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RISK-BASED APPROACH TO EVALUATE ALLIGATOR GAR ATRACTOSTEUS SPATULA AQUACULTURE IN FLORIDA
By
LAUREN N. LAPHAM
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
2019
© 2019 Lauren N. Lapham
To my family
4
ACKNOWLEDGMENTS
I thank the members of my supervisory committee, Drs. Jeff Hill, Quenton
Tuckett, and Josh Patterson, for their support and guidance with my research, scientific
writing, and professional development. Thanks also to my professors for their guidance
and education in the classroom.
I also thank those who assisted in my research, the project team and
stakeholders from the Florida Aquaculture Association, Florida Tropical Fish Farms
Association, Florida Department of Agriculture and Consumer Sciences, Florida Fish
and Wildlife Conservation Commission, U.S. Fish and Wildlife Service, Oklahoma
Division of Wildlife Conservation, University of Florida, and U.S. Geological Survey, who
were essential to the completion of this research. I thank the project team, Jeff Hill,
Quenton Tuckett, Josh Patterson, and Allison Durland Donahou, for their involvement
and input. In addition, I thank my family and friends for their continued support and
encouragement. I am particularly grateful to my parents and grandparents for their
support of my education.
Funding for this project came from the Florida Fish and Wildlife Conservation
Commission (FWC). The UF/IFAS Tropical Aquaculture Laboratory, director Craig
Watson, provided facilities for the stakeholder panel meeting. I especially thank the
grant management team, Kristin Summers, Sarah Funk, and Kelly Gestring (FWC); also
for assistance, David Boozer of the Florida Tropical Fish Farms Association, Tiffany
Conner of the Florida Aquaculture Association, and Chelsea Crandall (UF). Finally, I am
grateful for and thank the faculty, staff, and students at the UF/IFAS Tropical
Aquaculture Laboratory for their support.
5
TABLE OF CONTENTS page
ACKNOWLEDGMENTS .................................................................................................. 4
LIST OF TABLES ............................................................................................................ 7
LIST OF FIGURES .......................................................................................................... 8
LIST OF ABBREVIATIONS ............................................................................................. 9
ABSTRACT ................................................................................................................... 10
CHAPTER
1 INTRODUCTION .................................................................................................... 12
2 METHODS .............................................................................................................. 16
Biological Synopsis ................................................................................................. 16 Risk Screening ........................................................................................................ 17
Generic Analysis ..................................................................................................... 21
3 RESULTS ............................................................................................................... 29
Biological Synopsis ................................................................................................. 29 Alligator Gar Atractosteus spatula Biological Synopsis .................................... 34
Classification .............................................................................................. 34 Distribution ................................................................................................. 43 Biology ....................................................................................................... 58
Control ....................................................................................................... 65 Potential Florida Distribution ...................................................................... 66
Potential Impact ......................................................................................... 73
Risk Screening ........................................................................................................ 84 Generic Analysis ..................................................................................................... 87
Stakeholder Workshop and Generic Analysis .................................................. 87 Stakeholder Workshop Evaluation ................................................................... 94
4 DISCUSSION ....................................................................................................... 114
Data Gaps and Research Recommendations ....................................................... 118 Management Implications and Risk Mitigation ...................................................... 118
APPENDIX
A STAKEHOLDER GENERIC ANALYSIS WORKSHEET ....................................... 122
6
B WORKSHOP EVALUATION FORM ..................................................................... 126
LIST OF REFERENCES ............................................................................................. 128
BIOGRAPHICAL SKETCH .......................................................................................... 140
7
LIST OF TABLES
Table page 2-1 Stakeholder panel members’ affiliation and experience. Panel members were
not compensated or provided with travel funds by the project team for their participation ........................................................................................................ 26
2-2 Project team, affiliations, and title/expertise ....................................................... 27
2-3 Stakeholder presentations, presenters, and affiliations ...................................... 28
3-1 FISK scores for three assessors of Alligator Gar aquaculture in Florida (mean = 4; Δ = 2). The score is the overall score of each assessor, with the overall scores the sum of the scores in each section (Biogeography/Historical (1.01 to 3.05) and Biology and Ecology (3.01 to 8.05)). Scores <1 indicate low risk, scores ≥ 1 and ≤10.25 indicate medium risk ....................................................... 96
3-2 FISK version 2 assessment for Alligator Gar for Florida. The Q ID column corresponds to question identification codes in FISK. Answer codes are N = no, Y = yes, and ? = don’t know and are separated to show answers, justification, and certainty of the two independent assessors. Certainty codes are 1 = very uncertain, 2 = moderately uncertain, 3 = moderately certain, and 4 = very certain ................................................................................................... 98
3-3 Breakout groups and overall risk assessment results. Oponions different within groups where there are multiple risk ratings or certainty values. The composition of breakout groups differed for the two sections (establishment and consequences). Risk levels are H = High, M = Medium, and L = Low. Theoverall risk of establishment is the lower of the four ratings and the overall risk of consequences is the highest rating between environmental and economic (unless both are low, then social/political). The ORP is the average of establishment and consequences, rounded up. Certainty levels are as follows: VU = very uncertain, RU = reasonably uncertain, MC = moderately certain, RC = reasonably certain, and VC = very certain .................................. 112
3-4 Results of the evaluation of the stakeholder risk assessment workshop. All participation was anonymous, with seven attendees providing answers following the completion of the workshop ......................................................... 113
8
LIST OF FIGURES
Figure page 3-1 Alligator Gar........................................................................................................ 34
3-2 Juvenile Alligator Gar of normal and leucistic coloration .................................... 37
3-3 Juvenile Alligator Gar ......................................................................................... 38
3-4 Adult Alligator Gar .............................................................................................. 38
3-5 Adult world record Alligator Gar, 2.6 m, 148 kg .................................................. 39
3-6 Platinum (or snow) Alligator Gar ......................................................................... 41
3-7 Map of North American range occurrences of Alligator Gar, including the native range ........................................................................................................ 44
3-8 Known distribution of established Alligator Gar populations in the United States ................................................................................................................. 44
3-9 Map of sustaining, historic, remanent, and stocked populations of Alligator Gar throughout their native range ....................................................................... 45
3-10 Coloration of juvenile Alligator Gar ..................................................................... 62
3-11 Alligator Gar CLIMATCH source map ................................................................. 68
3-12 Alligator Gar CLIMATCH target map in Florida................................................... 69
3-13 RAMP map of climate match for Alligator Gar in the United States .................... 69
3-14 RAMP interpolated grid for A. spatula climate matching ..................................... 70
3-15 Bar chart of Alligator Gar literature produced from 1990-2018 ........................... 81
3-16 Distributions of certainty percentage for the answers to 49 questions of the FISK risk screening ............................................................................................ 97
3-17 Distributions of FISK risk category scores with the average and standard deviation ........................................................................................................... 111
4-1 FISK scores of five ornamental or food fish species compared to Alligator Gar ................................................................................................................... 121
4-2 Distribution of Alligator Gar in Mexico ............................................................... 121
9
LIST OF ABBREVIATIONS
ANSTF Aquatic Nuisance Species Task Force
BMP Best Management Practices
DPH Days Post Hatch
FISK Fish Invasiveness Screening Kit
FWC Florida Fish and Wildlife Conservation Commission
10
Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science
RISK-BASED APPROACH TO EVALUATE ALLIGATOR GAR ATRACTOSTEUS
SPATULA AQUACULTURE IN FLORIDA
By
Lauren N. Lapham
August 2019
Chair: Jeffrey E. Hill Major: Fisheries and Aquatic Sciences
Alligator Gar Atractosteus spatula is native to North America and has declined
throughout much of its range, including the Florida panhandle. Few data exist for
Alligator Gar in Florida; therefore, the Florida Fish and Wildlife Conservation
Commission implemented a harvest closure in 2006, making it illegal to take or possess
Alligator Gar without a permit. There is interest in Florida to culture Alligator Gar for food
and out-of-state ornamental sale, neither of which are currently permitted. Although
Alligator Gar is native, there is concern for invasiveness in areas of Florida outside of
the native range if commercial aquaculture were permitted. Before making decisions
concerning commercial culture, it is prudent to evaluate the risks of establishment and
impact in Florida. Invasiveness risk was assessed through an extensive literature review
and biological synopsis, risk screens, and a stakeholder-inclusive qualitative risk
assessment. The biological synopsis provided considerable information on invasive
potential and data gaps. The Fish Invasiveness Screening Kit (FISK) assessments
provided a preliminary risk estimate of non-invasive. An expert stakeholder panel
determined that the risk of Alligator Gar aquaculture was of moderate concern. The
overall risk of aquaculture was evaluated at the low end of medium and supported by a
11
federal risk screen. Discussion of risk mitigation concluded that aquaculture best
management practices are acceptable to reduce risks. Research and management
recommendations arising from the risk-based process are available for agencies and
industry to support decision making regarding permitting, restricting, or prohibiting
aquaculture of Alligator Gar and facilitate the development of risk management options.
12
CHAPTER 1 INTRODUCTION
Culture of non-native fish can be problematic because escape can result in
establishment and spread of non-native populations, which may cause negative impacts
such as habitat modification or native species decline (Cook et al. 2008; Hill 2008;
Cucherousset and Olden 2011). Yet, some of the most important aquaculture species
worldwide are cultured outside of their native range (e.g. carps and tilapia; Gozlan et al.
2010; Fitzsimmons et al. 2011). Non-native species dominate the largest segments of
Florida aquaculture, especially tropical aquarium fish (40% of Florida aquaculture value
in 2012; USDA-NASS 2013) and are important components of various commodity
groups. The use of native species in aquaculture could avoid negative impacts from the
introduction of non-native species and is important to consider (Ross et al. 2008).
Despite frequent calls in the literature, there are issues to consider with the use of
native fish in aquaculture (Ross et al. 2008; Cruz‐Casallas 2011; Saint-Paul 2017).
Native fish which escape from aquaculture may affect wild populations through
interbreeding, potentially reducing fitness of wild stocks (Weir and Grant 2005).
Therefore, cultured organisms not intended for local stocking, whether native or non-
native, are usually subject to regulations intended to reduce escape (FDACS 2016).
Risk analysis is an approach that can be used in aquaculture management to identify
hazards and resulting risks, and to effectively manage risks arising from potential
introduction of cultured organisms (Hardin and Hill 2012; Hill and Lawson 2015).
Interest in commercial culture of Alligator Gar in Florida as an ornamental and
food fish is increasing. Methodology for culturing Alligator Gar is well documented,
because the species is cultured in federal hatcheries (Private John Allen National Fish
13
Hatchery; Tishomingo National Fish Hatchery) for stock enhancement, and at
universities for research. Alligator Gar are easily maintained in captivity, spawn readily
under hatchery conditions, tolerate of a wide range of water quality conditions, and can
be raised entirely on artificial feed (Weed 1923; Mendoza et al. 2002a; Mendoza et al.
2002b; Clay et al. 2009). National and international ornamental markets and regional
food markets currently exist (Suttkus 1963; Buckmeier 2008; DiBenedetto 2009; Zullo
2009; Ichien 2011). However, the species is currently unavailable for commercial culture
in Florida due to the fishing ban which prohibits take or possession without a scientific
collectors’ permit (FWC 2019).
The Alligator Gar Atractosteus spatula is native to the western panhandle of
Florida, historically found west of the Econfina River (Lee et al. 1980; Boschung and
Mayden 2004; Froese and Pauly 2018). In recognition of population declines throughout
its native range and reduced catch in Florida, a harvest closure of Alligator Gar was
implemented in 2006 by the Florida Fish and Wildlife Conservation Commission (FWC
2019). The decline in Alligator Gar populations throughout their native range has been
attributed primarily to anthropogenic impacts including: habitat loss from stream
channelization, isolation of floodplains by levee construction and subsequent
development, and overharvesting (Etnier and Starnes 1993; Mettee et al. 1996).
Alligator Gar was historically targeted for eradication programs throughout their native
range because agencies considered Alligator Gar to be ‘trash fish’ and a nuisance
species, negatively impacting desired game fish (Scarnecchia 1992; Schultz 2004).
More recently, biologists and anglers consider Alligator Gar to be an integral component
14
of the native ecosystem as well as a valuable game and food fish (Scarnecchia 1992;
Fuller 2019).
The FWC determined that a risk analysis process would be necessary to
evaluate the potential for legal commercial culture of Alligator Gar in Florida. With the
ultimate goal of providing information for management decisions, an evaluation of
Alligator Gar aquaculture in Florida was completed under an expanded risk assessment
protocol. Risk assessment tools have been used extensively in Florida to support
agency management decisions (e.g. Arapaima Arapaima gigas (Hill and Lawson 2015);
Barramundi Perch Lates calcarifer (Hardin and Hill 2012); Grass Carp
Ctenopharyngodon idella (Zajicek et al. 2009); tilapia (Hill 2017); and marine
ornamentals (Zajicek et al. 2009)).
The risk assessment process for Alligator Gar aquaculture in Florida utilized an
established process consisting of three components: (1) a review of Alligator Gar
literature, (2) an internationally recognized rapid risk screen, and (3) a comprehensive
stakeholder meeting to perform a qualitative assessment of risk using a U.S. federal
methodology as framework. Of concern were potential risks associated with the
introduction of captive Alligator Gar into the environment (1) outside the native range in
north and peninsular Florida where they might establish, spread, and cause impacts
and (2) in the native range in the panhandle where they might negatively interact with
wild populations. The Fish Invasiveness Screening Kit (FISK) v2 (Lawson et al. 2013)
provided an initial estimate of risk and hazard analysis. Expert stakeholders completed
a comprehensive risk assessment using the U.S. Federal Generic Analysis approach
(ANSTF 1996). These components were used to complete the risk assessment
15
process, identify data gaps, compile and analyze data, and provide research and
management recommendations.
16
METHODS
Biological Synopsis
The biological synopsis is a compilation of Alligator Gar literature including
information on taxonomy, biology, and ecology, along with information that is useful for
the risk assessment process. The biological synopsis identifies data gaps and utilizes
information related to risk assessment, including factors indicative of invasion potential.
These factors include invasion history and establishment, climate matching, and
documented impacts. These elements are widely considered to be useful for
determining invasion potential (Kolar and Lodge 2002; Daehler et al. 2004; Marchetti et
al. 2004).
This component followed the standardized format used in previous evaluations of
non-native fishes (e.g. Arapaima, Barramundi, and Damselfish). Information for the
literature review was derived from primary literature, computer databases (Google
Scholar, Web of Science), invasive species database searches (USGS Nonindigenous
Aquatic Species database), and fish/aquatic life/distribution databases. Search terms
utilized during the literature review included the common names as well as current and
former scientific names for Alligator Gar (e.g. Lepisosteus spatula) and terminology
related to the various topics such as “Alligator Gar spawning period” and “Alligator Gar
aquaculture.” Literature was further analyzed using reference backtracking, citation lists,
perusal of investigators’ libraries, discussions with colleagues, hobbyist literature, and
online sources to supplement and fill relevant synopsis sections.
The biological synopsis provided information necessary for the risk screenings,
additional data for management agencies, and elucidates data gaps and future research
needs. Also included are sections where information is synthesized by the author to
17
discuss potential range and impacts in the risk assessment area. The biological
synopsis was included in stakeholder materials utilized for the completion of the
qualitative Generic Analysis and risk screens.
Risk Screening
The risk screen was completed for the assessment of Alligator Gar aquaculture
in Florida using the Fish Invasiveness Screening Kit version 2 (FISK v 2; Lawson et al.
2013). The FISK is an internationally recognized rapid risk screening tool used to
provide an initial estimate of risk, identify hazards, and determine if further assessment
is needed (Copp et al. 2005). The FISK is a semiquantitative tool that consists of
questions relating to biogeography/history and biology/ecology, resulting in an overall
risk score that is calibrated into three levels of potential risk, low, medium, and high
(Lawson et al. 2013). Increasing overall scores equate to increasing risks of
establishment and impacts for non-native freshwater fishes.
The FISK risk screening tool was developed from the Australian Weed Risk
Assessment model (Pheloung et al. 1999). The FISK tool was developed to assess
potential invasiveness of non-native freshwater fish in England and Wales, a temperate
zone climate (Copp et al. 2005, 2009; Lawson et al. 2013). In response to climate
limitations presented by FISK v1, the FISK v2 was developed to increase its utility in
warmer climates (Lawson et al. 2013). FISK questions and guidance were reviewed and
revised to extend climatic applicability to additional climatic regions (e.g. tropical and
subtropical environments; Lawson et al. 2013). The FISK has been applied in 35 risk
assessment areas in 45 countries, with 1,973 FISK assessments completed by 70 +
experts on 372 taxa (Vilizzi et al. 2019). There are at least five published applications
for Florida, or that include Florida in the risk assessment area (Lawson et al. 2013 –
18
FISK v2; Lawson et al. 2015 – Florida FISK calibration; Hill et al. 2014 – Glofish FISK,
Hill et al. 2017 – Ornamentals in the United States; Hill and Lawson 2015 - Arapaima;
see also Vilizzi et al. 2019).
For Florida, a FISK calibration threshold of 10.25 was calculated to distinguish
between invasive and non-invasive species (Lawson et al. 2015). The calibrated
threshold correctly classified 76% of invasive fishes and 88% of noninvasive fishes
(Lawson et al. 2015). In Florida, low risk scores are ≤ 0, medium risk scores are >0 to
10.25, and high scores are ≥10.25 (Lawson et al. 2015).
Risk assessment considers both potential invasiveness and the possible impacts
of invasion, with FISK guidance defining high risk species as potentially invasive while
low and medium scores are considered non-invasive. Low risk results principally mean
there is little need for further assessment, and high risk means there is a need to assess
further due to potential hazards presented. Medium risk is more complex because it can
mean to assess the species further (potentially hazardous) or to stop assessment
depending on the type of species and what factors added to or detracted from the
overall score. Generally, low and medium species are unlikely to have moderate to
severe impacts on the risk assessment area, while they have the potential to establish,
the risks and impacts are lower. Should a low or medium risk species establish, the
impacts are more likely be less noticeable or severe, while a high-risk species is more
likely to have noticeable impacts upon establishment and is more likely to establish.
The FISK consists of 49 questions that result in an overall risk score, or sum,
ranging from -11 to 53. The range of values for each question contributes to an overall
score that is calibrated to three levels of potential risk, low, medium, and high (Lawson
19
et al. 2013). Higher overall scores equate to increasing risks of establishment and
impacts for non-native freshwater fishes. The answers to FISK questions generate or
modify the score of other questions. Specific questions relate to biology and ecological
traits and can be answered by ‘yes’ or ‘no’, with justification allowing for explanations of
data interpretation and references. Particular questions were developed to allow for the
assessor’s judgement, such as questions regarding impacts of the species on the risk
assessment area.
Assessor expertise and risk sensitivity are important factors to consider for the
risk assessment process. The subjective assessors (screeners) are expected to follow
the explanatory guides to each question and provide brief justification (e.g. citations) for
responses and certainty associated with each answer. Justification provides
transparency in the risk assessment process, facilitates discussion upon disagreement,
and the opportunity for input as information or feedback is returned. Information and
questions can be interpreted differently by assessors, with similar justifications
associated with differing responses.
The FISK assessments were performed by three independent assessors to
provide an estimate of risk (Table 2-2), with one additional project team member
reviewing (Table 2-2) assessments to ensure quality control and identify potential errors
for assessors to review. Multiple assessors result in a mean FISK score that is closer to
the real risk value of the species (Copp et al. 2013). Training in risk assessment and
related tools was completed prior to the execution of the FISK screenings, with two of
the three assessors having numerous assessments and associated publications for
Florida. Assessor three completed two training sessions consisting of multi-day direct
20
training with the project director, several days of specific training, plus graduate level
coursework in risk assessment.
Utilized in the risk screen is the climate matching program CLIMATCH
(Australian Bureau of Rural Sciences 2010). CLIMATCH is a peer reviewed, publicly
available program that compares the similarity of climate stations in a source region and
target region based on similarity index of 16 factors (precipitation, temperature). The
software produces maps of the native region (source) and the risk assessment or target
region, with source locations derived from literature. The risk assessment area for
Alligator Gar is Florida. The source map (Figure 3-11) includes blue and red points, with
blue representing weather stations not used for the source map and red representing
stations that were used. A climate 6 score is the acceptable similarity or measure of
suitable climate between the source region and target region, with the algorithm of the
system determining the climate distance between the source map and target area, with
the level of the match determined by the closest standard score between input sites and
target sites. A climate 6 score or higher is considered suitable climate for the organism.
The area of the red points is proportional to the number of match cells that this data
point contributed to the target region. The target region map (Figure 3-12) was used to
calculate the proportion of weather stations in Florida with a comparable similarity value
(climate 6 score). The target region map uses a scale of 1 to 10, ten being the highest
match. The map illustrates the proportion of weather stations with climate 6 scores or
higher matching the source region. The USFWS federal protocol was used to determine
values for classifying CLIMATCH results for high (≥0.103), medium (0.005<x<0.103),
and low matches (0.000<x<0.005; Hoff 2016). The source location for Alligator Gar was
21
derived from the Global Biodiversity Information Facility (www.gbif.org/en) and
additional primary resources.
Individual overall scores and the mean scores of the three assessors for Alligator
Gar were compared to calibrated threshold for Florida (10.25) to provide an estimate of
low, medium, or high risk for the risk assessment area (Florida). The FISK and
CLIMATCH results were used to ascertain research gaps and identify risks that may be
important for decision making in Florida. Recommendations were made for
management and future research needs to mitigate identified knowledge gaps.
Generic Analysis
The stakeholder workshop was assembled to complete a full risk assessment
with a panel of experts to evaluate the risks of, and respond to questions of concern, for
Alligator Gar aquaculture in Florida. The qualitative risk assessment conducted was
based on the federal Aquatic Nuisance Species Task Force (ANSTF 1996)
methodology (hereafter ‘Generic Analysis’). Risks were evaluated for north Florida and
peninsular Florida, regions outside of the native range of Alligator Gar in Florida, as well
as within the native range (the western panhandle). Risks were evaluated to determine
the risk potential of Alligator Gar establishment, spread, and impacts in peninsular
Florida and the potential and impacts of genetic interactions with cultured and wild
Alligator Gar in the panhandle.
A Generic Analysis of non-native species, or pathways of introduction, has been
used at the federal and state level to evaluate the risks of non-native species and
pathways (Hill and Zajicek 2007), including use by Florida agencies in the risk
assessment area (Zajicek et al. 2009; Hardin and Hill 2012). The Generic Risk Analysis
is a qualitative assessment of risk, resulting in an overall risk potential (ORP) of low,
22
medium, or high. For the Generic Analysis, a low risk rating means the organism is of
little concern, or acceptable risk, while medium and high risk are considered
‘unacceptable risk’ and require some level of mitigation (ANSTF 1996).
The qualitative analysis is composed of multiple sections; (1) probability of
introduction; (2) probability of establishment (i.e. colonization potential, spread
potential), and (3) consequences of establishment (i.e. economic, environmental
impacts). The sections consist of seven questions that each have an associated rating
level, certainly, and justification. The first four questions address the probability of the
organism being in the pathway, entry potential, colonization potential, and spread
potential (probability of introduction and establishment). The last three questions
address the impacts of establishment, specifically: economic impacts potential,
environmental impacts potential, and perceived social and political impacts. Each
question has a low, medium, and high rating for risk, and five associated certainty levels
ranging from Very Uncertain, Reasonably Uncertain, Moderately Certain, Reasonably
Certain, to Very Certain with associated justifications to evaluate invasive potential and
establishment impacts. Certainty, the level of confidence associated with a response,
levels can change as data becomes available and reflects the assessors risk tolerance
and experience with risk assessment.
To determine the overall risk of introduction and establishment, the lowest rating
of the four questions is selected. The lowest rating is selected as a conservative
measure, as each of the elements must occur (conditional probability) for an organism
to establish. The overall risk rating for impacts of establishment is determined by
selecting the highest rating between environmental and economic impacts. If both
23
environmental and economic impacts are rated low, the social/political ranking will be
used to determine the overall impacts of establishment. The Overall Risk Potential
(ORP) is the conservative average (rounded up) of the risk of introduction and
establishment and risks of impacts. Rounding up is a conservative measure to
counteract the uncertainty associated with the risk assessment process and biological
situations (ANSTF 1996).
An expert stakeholder panel was selected to represent a wide range of expertise
and experience, with eleven panel members recruited from state and federal agencies,
industry, and academia, including two members of the Alligator Gar Technical
Committee of the Southern Division of the American Fisheries Society (Table 2-1).
Stakeholders were selected by the project team or the entities that they represented,
and participation was confirmed by email. Stakeholders were invited to attend the
workshop and complete the qualitative risk assessment.
Panel members received information packets for the qualitative assessment by
email, two weeks prior to the workshop held at the UF/IFAS Tropical Aquaculture
Laboratory in Ruskin. The packet materials were comprised of the Alligator Gar
biological synopsis, the FISK risk assessments, two referred publications describing and
providing examples of the FISK assessment process (Lawson et al. 2013; Hill and
Lawson 2015), a report from the Aquatic Nuisance Species Task Force describing the
Generic Analysis (ANSTF 1996), and a publication providing an example of the use of
Generic Analysis (Hardin and Hill 2012). All panel members were asked to review
informational materials prior to the stakeholder workshop to familiarize themselves with
24
content and procedures, as well as to provide comments or corrections for the biological
synopsis and FISK assessments. Some of these materials are included in the results.
The stakeholder workshop and qualitative assessment took place over two days,
April 29 and 30, 2019. Eight stakeholders attended the workshop, with day 1 involving
introductions of stakeholders and the project team, an overview of the goals and
objectives, and five informal presentations (Table 2-3) to provide additional background
information on Alligator Gar, risk assessment, non-native species, and best
management practices, followed by a question and answer session. Day 2 included a
brief discussion of the agenda and a question and answer session prior to the
completion of the qualitative risk assessment.
The qualitative risk assessment was completed in two breakout group sessions
composed of varying stakeholder members, with the first session evaluating the
probability of introduction and establishment (Appendix A) followed by a group
discussion and a second breakout session discussing potential impacts of introduction
(Appendix A). The groups were selected to provide equal representation from all
stakeholder backgrounds and allow greater for the opportunity for stakeholders to put
forward thoughts, questions, and opinions. Each breakout group was assigned a project
team member to facilitate discussions, with a moderator available to answer questions
for all groups throughout the process. The group discussion following each breakout
group, as well as the final group discussion, was used to determine the ORP for each
breakout group as well as the collective stakeholder panel. The project team facilitated
the meeting and attempted to answer stakeholder questions throughout the risk
assessment related to facts, the process, or direct questions to the panel members. The
25
project leader (JEH) was the main facilitator and moderator for the workshop. Lastly, a
facilitated group discussion on impacts, the overall risk level, and risk mitigation
occurred after the completion of the generic risk assessment.
The overall group discussion following both breakout groups and subsequent
discussions attempted to result in a consensus for the risk level of Alligator Gar
aquaculture in Florida, but consensus was not required. A discussion of risk mitigation
was introduced after the Generic Analysis to discuss current best management
practices and whether there would need to be further changes in management and
protocols to mitigate risk to an acceptable level. Before concluding the stakeholder
workshop, panel members were invited to complete an anonymous qualitative
evaluation (Appendix B) assessing the stakeholders’ participation, satisfaction,
agreement, and requesting further comments of the stakeholder qualitative assessment.
Any further comments or edits from the stakeholder panel for the Alligator Gar biological
synopsis and FISK v2 risk screenings were solicited by the project team and requested
to be sent within three weeks of the stakeholder workshop. The deadline for comments
on the materials, process, outcome, or associated aspects of the risk analysis process
was May 22, 2019.
Information from the biological synopsis, FISK risk screen, stakeholder panel,
and Generic Analysis was analyzed to identify research gaps and risk factors that may
be important for management decisions in Florida, with recommendations made to fill
the research gaps. Additional management recommendations based on information
generated from this project was also provided.
26
Table 2-1. Stakeholder panel members’ affiliation and experience. Panel members were not compensated or provided with travel funds by the project team for their participation, though dinner (April 29), breakfast (April 30), and break refreshments (both days) were provided.
Stakeholder Affiliation Title/Experience
Brandon Barthel
Florida Fish and Wildlife Conservation Commission
Geneticist, Fish and Wildlife Research Institute
John Galvez U.S. Fish and Wildlife Service Project leader
Howard Jelks U.S. Geological Survey Research Fish Biologist, Wetland and Aquatic Research Center
Eric Johnson Florida Fish and Wildlife Conservation Commission
Regional Fisheries Administrator, Division of Freshwater Fisheries Management
Cortney Ohs University of Florida, Program in Fisheries and Aquatic Sciences
Associate Professor, Aquaculture, Indian River Research and Education Center
David Rawlins Florida Aquaculture Association Commercial Fish Farmer
Portia Sapp Florida Department of Agriculture and Consumer Services
Director, Division of Aquaculture
Andrea Sizemore
Florida Fish and Wildlife Conservation Commission
Risk Assessment Coordinator, Wildlife Impact Management Section
John Skidmore Florida Tropical Fish Farms Association
Commercial Fish Farmer
Richard Snow Oklahoma Department of Wildlife Conservation & SDAFS Alligator Gar Technical Committee
Biologist, Oklahoma Fishery and Research Laboratory
Matthew Wegener
Florida Fish and Wildlife Conservation Commission & SDAFS Alligator Gar Technical Committee
Biologist, Blackwater Research and Development Center
27
Table 2-2. Project team, affiliations, and title/expertise.
Project Team Affiliation Title/Expertise
Allison Durland Donahou University of Florida, School of Natural Resources and the Environment, Tropical Aquaculture Laboratory
Ph.D. Student under Dr. Jeffrey Hill; ecology and life history of non-native aquatic species, risk assessment
Jeffrey Hill University of Florida, Program in Fisheries and Aquatic Sciences, Tropical Aquaculture Laboratory
Associate Professor; ecology of non-native fishes; risk analysis; project principal investigator
Lauren Lapham University of Florida, Program in Fisheries and Aquatic Sciences, Tropical Aquaculture Laboratory
M.S. Student under Dr. Jeffrey Hill, risk assessment of Alligator Gar aquaculture in Florida
Josh Patterson University of Florida; Program in Fisheries and Aquatic Sciences, Florida Aquarium at Apollo Beach
Assistant Professor; restoration aquaculture, Alligator Gar aquaculture
Quenton Tuckett University of Florida, Program in Fisheries and Aquatic Sciences, Tropical Aquaculture Laboratory
Research Assistant Scientist; aquatic ecology and non-native species, risk analysis; project co-principal investigator
28
Table 2-3. Stakeholder presentations, presenters, and affiliations.
Presentation Title Presenter Affiliation
Alligator Gar Matthew Wegener FWC
Nonnative Fish in
Florida
Jeffrey Hill UF/IFAS Tropical Aquaculture
Laboratory
Aquaculture BMPs
and BMP evaluation
Portia Sapp
Quenton Tuckett
FDACS
UF/IFAS Tropical Aquaculture
Laboratory
Risk Assessment:
FISK and Generic
Analysis
Jeffrey Hill UF/IFAS Tropical Aquaculture
Laboratory
29
CHAPTER 3 RESULTS
Biological Synopsis
The study species for the biological synopsis was Alligator Gar Atractosteus
spatula, the genus Atractosteus consists of three species, with Alligator Gar being the
largest of the gar family and the most widespread of the genus. The historic range of the
species consists of 14 states, with six formally listing the species rare or extirpated
(Buckmeier 2008; Jelks et al. 2008).
Alligator Gar are the second largest freshwater fish in North America (Buckmeier
2008) and native to the southeast United States and Mexico; historically found in
coastal rivers of the panhandle of Florida, from the Econfina river west along the Gulf
Coastal Plain to Veracruz, Mexico, throughout the Mississippi in Alabama and brackish
water of the Gulf Coast and Mobile-Tensaw Delta, north in the Mississippi river basin
drainage to southwestern Ohio, Missouri, southern Illinois, and the lowermost
Cumberland and Tennessee Rivers (Lee et al. 1980; Boschung and Mayden 2004;
Froese and Pauly 2018). Literature indicates that Alligator Gar are the most salt tolerant
of the gar species, with adults being found to tolerate seawater up to 35 ppt (Suchy
2009; Green et al. 2015). The northernmost native range has temperatures reported as
low as 1℃, and high temperatures in the native range have been reported up to 30℃
(Salnikov 2010). The critical thermal maximums of Alligator Gar range from 39.2-44.7℃
(Fernando et al. 2015).
Primary literature indicates that Alligator Gar live over 50 years (Ferrara 2001;
Boschung and Mayden 2004; Roberts and Harrel 2006; Salnikov 2010; Buckmeier et al.
2016) with the minimum age of maturity ranging from 4-11 years. Recent research
30
indicates younger ages of sexual maturity (4-6 years; Boschung and Mayden 2004;
Salnikov 2010; Ferrara et al. 2015). Volitional spawning of males and females at 4 years
of age was observed after undergoing a rapid change in osmotic environment and
handling (Patterson et al. 2018). In literature, spawning is associated with flooded,
submerged, and weedy areas (Page and Burr 1991; Schultz 2004; Salnikov 2010;
Froese and Pauly 2018). Reproduction in Florida has been confirmed in the Escambia
River, with spawning occurring in flooded backwaters that need a minimum inundation
period of 5 days (ideally 60) with water temperatures between 20℃ and 30℃ (Echelle
and Riggs 1972). There are research gaps regarding spawning requirements for
Alligator Gar, meaning it is unknown whether these conditions are mandatory for
successful spawning and recruitment. If these conditions are necessary, these factors
would limit reproduction and successful recruitment in some regions of Florida.
Spawning requirements in aquaculture are well known. Alligator Gar is currently
cultured in federal hatcheries in the United States (e.g. the Private John Allen National
Fish Hatchery; Tishomingo National Fish Hatchery) for restoration purposes.
The most likely mechanisms of impact in the risk assessment area would be
predation on native species, competition with native species for food, and hybridization
with native gar. The introduction of other large, predatory fish has had negative impacts
documented in Florida. The predatory effects of the non-native Flathead Catfish
Pylodictis olivaris has reduced the abundance of Redbreast Sunfish Lepomis auratus
and two bullhead catfishes Ameiurus spp. the Apalachicola River (Dobbins et al. 2012).
Despite Alligator Gar being a large, predatory, piscivorous fish, reintroduction studies
(Richardson 2015) indicate that there is little evidence of prey depletion or competition.
31
Diet studies in a re-introduced population in western Kentucky suggests opportunistic
feeding behavior and a lack of diversity in abundant prey, resulting in dietary overlaps
for four sympatric gar species (Richardson 2015).
Hybridization has been documented in the wild and aquaria, with most concern
associated with native Longnose Gar Lepisoteus osseus. There is ongoing research in
Florida to assess the possibility of hybridization with other gar species in the Pensacola
Bay watershed (Wegener 2018).
Factors that consistently influence invasion success across taxa and regions
include invasion history, high climate match and propagule pressure (Hayes and Barry
2008; Copp et al. 2010). The literature review revealed minor history of introduction of
individuals outside of the native range of Alligator Gar, with no successfully established
populations indicated in literature (Fuller 2019). Alligator Gar have a high climate 6
score (0.92) in Florida, a characteristic that is indicative of higher invasion potential and
increased risk. The most suitable climate match for Alligator Gar was in the western
Panhandle, where Alligator Gar are native, as well as across north Florida towards the
east coast and south along the east coast to St. Lucie County. While these areas have
the highest climate match, the climate match illustrated that most of Florida is a suitable
climate for Alligator Gar with a similarity score of ≥ 6. Most of Florida has suitable
habitat for adult Alligator Gar, but there is uncertainty regarding potential habitat
availability for spawning and recruitment success.
Florida has seemingly suitable habitat in the coastal river systems along the
northern Gulf of Mexico coast east of the current range of Alligator Gar, including the
Suwannee River in Florida’s Big Bend. Most of these systems periodically flood
32
(SRWMD 2017) presenting potential spawning and nursery habitat for Alligator Gar.
Rivers draining on the west coast of Florida may be less suitable for Alligator Gar,
exceptions may include the Peace River, as most systems have relatively small
floodplains and short periods of floodplain inundation that are not ideal nursery or
spawning habitat for Alligator Gar. South Florida has extensive wetlands that may
provide suitable habitat if Alligator Gar can tolerate low water periods by utilizing canals
or solution holes as refuge habitat. Potential detractors for the suitability of the east
coast habitats is the few potential spawning/nursery areas, however, it was discussed
during the risk assessment process that Alligator Gar have exhibited volitional spawning
in earthen ponds following handling, transfer to a new pond, and a change in salinity
(Patterson et al. 2018). Lake Okeechobee or lakes within the St. Johns River basin may
present suitable habitat if Alligator Gar can spawn in more lentic systems. The
Longnose Gar is a lotic spawner that spawns in channels rather than backwaters,
however, the species successfully spawns and recruits in both systems (Holloway 1954;
Johnson and Noltie 1996; Gandy et al. 2012). An aspect of Alligator Gar biology that
may present limitations to movement is the timing of flooding. Literature states that
Alligator Gar spawning is associated with flood events (Page and Burr 1991; Schultz
2004; Salnikov 2010; Froese and Pauly 2018), while the Alligator Gar has an extended
spawning period across its native range (January to September; Echelle and Riggs
1972), flood periods in the peninsula may not coincide with spawning habits.
Research gaps identified in the literature review were associated with
reproduction, impacts of introduction, population genetics, and hybridization. There is
33
limited information for Alligator Gar in Florida, with movement and genetic research
ongoing (Wegener 2018).
Increased interest in Alligator Gar for sport and conservation purposes
(Buckmeier et al. 2016) was reflected in the literature review, with publications showing
a marked increase in the mid 2000’s (Figure 3-15). The decline of Alligator Gar
populations throughout most of their native range has resulted in an increased interest
in aquaculture of Alligator Gar. Resources for the literature review varied, with 115
references listed in the biological synopsis. The characterization of literature published
also reflects the change in perception regarding Alligator Gar. Web of Science
(wcs.webofkowledge.com) lists 84 publications for Alligator Gar, with nearly half (47%)
listed as fisheries publications.
Data and information that were found to be lacking during the literature review
was noteworthy as the lack of information would likely be interpreted as an element of
higher risk, potentially changing the risk assessment of Alligator Gar aquaculture in
Florida. It is important to identify information and data gaps to aid in providing
recommendations and identifying future research needs.
34
Alligator Gar Atractosteus spatula Biological Synopsis
Figure 3-1. Florida Fish and Wildlife Conservation Commission. Alligator Gar. May 30, 2014. Escambia River. Source: Florida Fish and Wildlife Conservation Commission. 2019. Florida Fish and Wildlife Conservation Commission, Tallahassee, Fl.
Classification
Taxonomy, common names, and references
Super Class: Actinopterygii
Class: Holostei
Order: Lepisosteiformes
Family: Lepisosteidae
Genus: Atractosteus
Atractosteus spatula (Lacepède, 1803)
English common names for the species include Alligator Gar, Gemfish, Great
Gar, Garpike, Mississippi Alligator Gar or Gator Gar (Ross 2001; Froese and Pauly
2018).
The Alligator Gar was first described in 1803 as Lepisosteus spatula (Lacepède,
1803); synonyms include Litholepis adamantinus Rafinesque, 1818, Atractosteus
adamantinus (Rafinesque, 1818), Lepisosteus ferox Rafinesque, 1820, Lepisosteus
35
berlandieri Girard, 1858, and Atractosteus lucius Duméril, 1870 (Froese and Pauly
2018). FishBase (Froese and Pauly 2018) also lists Esox cepedianus Shaw, 1804 as an
ambiguous synonym of the Alligator Gar. The name was changed to Atractosteus
spatula in 1976 by Wiley to recognize two genera of gars (Wiley 1976; Goddard 2009).
The genus Atractosteus derives from the Greek word for spindle, atractus, and osteos,
meaning bony. The species name spatula derives from the Latin derivative of the Greek
word spathe, which refers to a tool with a broad, flat blade.
The family Lepisosteidae represents two genera of gar, containing 7 species
total: shortnose or broadhead gars Atractosteus (Rafinesque 1820) and longnose gars
Lepisosteus (Lacepède 1803; Salnikov 2010). Lepisosteidae are survivors of a group
that first occurred in the upper Permian period and flourished in the Triassic and
Jurassic periods. The family is known for long, sharply toothed jaws; the placement of
dorsal and anal fins far back on the body; and diamond shaped ganoid scales (Page
and Burr 1991). Gars are considered primitive fish due to the characteristic ganoid
scales, abbreviated heterocercal tail, and highly vascularized physostomous swim
bladder that can be used as a lung to gulp air at the surface (Page and Burr 1991).
Atractosteus have two rows of conical teeth on the maxilla. One row of teeth is
located on the preorbital bone and is part of the maxilla while the second row is located
inside the first row and located on the palatal bone (Page and Burr 1991; Schultz 2004).
The genus Lepisosteus has only one row of teeth that are located on the preorbital bone
(Page and Burr 1991; Boschung and Mayden 2004). There are three species of
shortnose gars: A. spatula, Cuban Gar A. tristoechus, and Tropical Gar A. tropicus.
Alligator Gar is the largest of the seven species and the most widespread Atractosteus.
36
Alligator Gar is often mistaken with the more commonly encountered gar species
such as the Shortnose Lepisosteus platostomus or Spotted Gar Lepisosteus oculatus
(USFWS 2016) or the Florida Gar Lepisosteus platyrhincus in much of Florida. Of the 7
gar species, Alligator Gar is considered uncommon, with increased abundance in
swamps and bayous in the southern parts of the United States (Page and Burr 1991).
Physical description and identifying characteristics
Alligator Gar grows considerably larger than other gars found in North America,
Central America, and Cuba (Ross 2001; Boschung and Mayden 2004; Fuller 2019).
Alligator Gar has a distinctive broad snout which differentiates them from other gar
species in the United States. This species has a large, cylindrical body covered in
heavy, interlocking diamond shaped ganoid scales (Ross 2001; Schultz 2004). Alligator
Gar also has triangular and laterally compressed gill rakers (Ross 2001; Schultz 2004;
Froese and Pauly 2018). The broad short snout distinguishes the Alligator Gar from
other gar species in the United States. The species, like others of its genus, has two
rows of teeth on its upper jaw (Page and Burr 1991; Schultz 2004). Alligator Gar, similar
to other gar species, have a rounded heterocercal caudal fin, a single dorsal fin that is
placed far on the back and above the anal fin, and evenly spaced pectoral, ventral, and
anal fins on the lower half of the body (Schultz 2004). There are 34-38 transverse scale
rows between the anal fin and middorsal position (Ross 2001). Alligator Gar has a dark
olive brown color, occasionally black, on the dorsal and ventral planes that becomes a
yellow to white color towards the ventral side (Page and Burr 1991; Ross 2001;
Boschung and Mayden 2004; Schultz 2004). The body is occasionally spotted or
mottled with large black spots (Page and Burr 1991; Schultz 2004). The dorsal, anal,
37
and caudal fins have a dark brown background with dark spots (Ross 2001). The
Alligator Gar has 7-10 dorsal rays, 7-10 anal rays, and 11-15 pectoral rays (Ross 2001).
The species has 58-62 lateral scales, 48-54 predorsal scales, and 59-66 gill rakers
(Page and Burr 1991). The head, from tip of the snout to occipent is 3.1-4.6 inches total
length; from snout tip to the anterior rim of orbit is 4.7-6.4 inches total length (Boschung
and Mayden 2004).
Figure 3-2. U.S. Fish and Wildlife Service. Juvenile Alligator Gar of normal and leucistic coloration. March 3, 2015. Source: United States Fish and Wildlife Service. 2019. United States Fish and Wildlife Service, Washington, D.C. Reprinted with permission from the U.S. Fish and Wildlife Service Online, https://www.fws.gov/ (January 4, 2019).
38
Figure 3-3. Florida Fish and Wildlife Conservation Commission. Juvenile Alligator Gar. 2018. Source: Wegener, M. 2018. Annual Project Report: Florida Fish and Wildlife Research Institute - Freshwater Fisheries Research. Florida Fish and Wildlife Conservation Commission, Tallahassee, Fl.
Figure 3-4. U.S. Fish and Wildlife Service. Adult Alligator Gar. 2019. Source: United States Fish and Wildlife Service.2019. United States Fish and Wildlife Service, Washington, D.C. Reprinted with permission from the U.S. Fish and Wildlife Service Online, https://www.fws.gov/warmsprings/ (January 5,2019).
39
Adults, on average, are 1.2-1.8 meters total length, but the species can grow up
to 3.1 meters total length (Suttkus 1963; Boschung and Mayden 2004; Salnikov 2010;
Froese and Pauly 2018). Adults can weigh 45–73 kg; however, they have been found to
159 kg (Boschung and Mayden 2004; Salnikov 2010; FishBase 2018). The largest
Alligator Gar recorded in Florida was 60 kg, collected by researchers in 2011 in the
Yellow River (FWC 2019a).
The world record Alligator Gar was estimated to be 94 years old; it measured 2.6
meters and 148 kg (Figure 3-5; Gemming 2017). It was caught in 2011 in Lake Chotard,
Mississippi (Love 2011).
Figure 3-5. Travis Fillmen. Adult world record Alligator Gar, 2.6 m, 148 kg. July 2, 2015. Vicksburg, Central Florida Aquarium Society. Source: Fillmen, T. 2015. Massive 327 Pound Alligator Gar Measures Over 8 Feet Long. Central Florida Aquarium Society. Reprinted with permission from the Central Florida Aquarium Society, https://cflas.org/2015/07/02/massive-327-pound-alligator-gar-measures-over-8-feet-long/ (January 4, 2019).
40
Platinum or Snow Alligator Gars (Figure 3-6) are a color variant of the Alligator
Gar; the gar are completely white as a result of a pigmentation disorder, leucism, which
is a genetic mutation that inhibits pigment deposition resulting in white, pale, or patchy
coloration of the scales (https://www.merriam-webster.com/dictionary/leucism). Platinum
Alligator Gar are popular and highly valued in the ornamental fish trade, especially
overseas. The low occurrence of Platinum Alligator Gar makes them highly valued and
also expensive; recent prices for 6-inch Platinum Alligator Gar are ~$1,250 online
(https://exoticfishshop.net/product/platinum-aligator-gar/) and reported $5-20,000 for a
12” leucistic Alligator Gar (personal communication Craig Watson, University of Florida).
The value of normal coloration Alligator Gar is still high, with an estimated $15
wholesale price for a 4” juvenile.
41
Figure 3-6. Photo courtesy of author. Platinum (or snow) Alligator Gar. January 4, 2019. Source: Lapham, L. 2019. Platinum (or snow) Alligator Gar. University of Florida, Institute of Food and Agricultural Sciences, Tropical Aquaculture Laboratory. Ruskin, Fl.
Genetics
Initial genetic studies found little mixing of estuarine and river (interior) Alligator
Gar populations (Bohn et al. 2013). More recently, Bohn et al. (2015) sampled Alligator
Gar from 16 sites across their native range and genotyped them for 8 microsatellite loci.
This study found 5 genetically distinct regions: the Rio Grande River and Choke Canyon
Reservoir, the Brazos River, eastern Texas including the Trinity River, the Mississippi
River drainage, and the northern Gulf Coast including coastal sites from southern
Louisiana to the Florida panhandle.
Hybridization between Alligator Gar and Longnose Gar Lepisosteus osseus is
documented in captivity (Herrington et al. 2001). Hybridization between wild Alligator
42
Gar and Longnose Gar has been documented (Bohn et al. 2017). Hybridization has
never been documented in Florida, despite the sympatric occurrence of native Alligator
Gar, Longnose Gar, and Spotted Gar in the panhandle. Studies are currently underway
to examine whether hybridization is occurring in the Escambia, Blackwater, and Yellow
Rivers (Wegener 2018).
A combination of otoliths and mitochondrial DNA has been used to better
understand population structure of Alligator Gar in the Guadalupe River (Texas) where
freshwater systems transition to saltwater bays of the Gulf of Mexico (Daugherty et al.
2017b). Three distinct life histories were revealed: river resident, transient, and bay
resident. River resident species were considered exclusive to freshwater and found
most commonly in the upper reaches of the river. Transient fish used both river and bay
habitats and were most commonly found in the lower reaches of the river. Bay fish were
exclusive to brackish water (13 ppt) and were the least common (Daugherty et al.
2017b). Mitochondrial DNA indicated that haplotype diversity was lowest in the upper
river, indicating limited gene flow compared to the lower river and bay (Daugherty et al.
2017b). The differences in Alligator Gar movement and genetics along the interface of
the river bay continuum indicated a river resident stock that dominates the upper river
and a transient stock that dominated the lower river and bay (Daugherty et al. 2017b).
There is genetic differentiation between coastal and inland Alligator Gar
populations. Juvenile Alligator Gar were collected from an inland population (St.
Catherine Creek National Wildlife Refuge, Mississippi) and a coastal population
(Rockefeller State Wildlife Refuge, Louisiana) to compare salinity regulatory ability
(Allen et al. 2015). Allen et al. (2015) acclimated both populations for two weeks to 0 or
43
20 ppt and 10 or 30 °C. After the acclimation period survival, gill Na+, K+-ATPase
activity, plasma osmolality, and plasma and gut fluid ion concentrations were sampled
and found to be similar between populations despite genetic differentiation. It was noted
by Allen et al. (2015) that neither population regulated ions well at 10 °C and 20 ppt.
Distribution
Native range
Alligator Gar is native to North America from the Econfina River, Florida, west
along the Gulf Coastal Plain to Veracruz, Mexico, including the Mississippi Sound in
Alabama and brackish water of the Gulf Coast and Mobile-Tensaw Delta; north in the
Mississippi river basin drainage to southwestern Ohio, Missouri, southern Illinois, and
the lowermost Cumberland and Tennessee Rivers (Lee et al. 1980; Boschung and
Mayden 2004; Froese and Pauly 2018). The species ranges from 44-20° N and 101-
80°W (Salnikov 2010).
In the Florida panhandle, Alligator Gar are found in coastal rivers flowing into the
northern Gulf of Mexico (Boschung and Mayden 2004). Recent studies indicate that
Alligator Gar only occur in Gulf Coast rivers west of the Apalachicola River; historic
records indicate populations of Alligator Gar in Choctawhatchee River, Escambia River,
and Econfina Creek (Hoehn 1998). Wegener (2018) notes personal observations of
Alligator Gar in the Yellow and Blackwater Rivers. There are reports of Alligator Gar in
the Gulf of Mexico; however, those sightings are
rare(https://www.nationalparkstraveler.org/2017/07/alligator-gar-spotted-along-floridas-
gulf-islands-national-seashore).
44
Figure 3-7. GBIF. Map of North American range occurrences of Alligator Gar, including the native range. Occurrences in Peninsular Florida are misidentifications and not representative of established populations of Alligator Gar. December 20, 2019. Source: Global Biodiversity Information Facility (GBIF). 2019. http://www.gbif.org.
Figure 3-8. United States Geological Survey. Known distribution of established Alligator Gar populations in the United States. September 1, 2018. Source: United States Geological Survey. 2019. Alligator Gar Atractosteus spatula. United States Geological Survey. https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=755
45
Figure 3-9. Florida Fish and Wildlife Conservation Commission. Map of sustaining, historic, remnant, and stocked populations of Alligator Gar throughout their native range. 2019. Source: Florida Fish and Wildlife Conservation Commission. 2019. Alligator Gar presentation, Alligator Gar stakeholder meeting. Florida Fish and Wildlife Conservation Commission, Tallahassee, FL.
Expansion/contraction
Alligator Gar are imperiled or rare throughout much of their native range,
particularly around the perimeter of the native range (Buckmeier 2008). Abundance in
some regions has declined due to unregulated fishing, eradication efforts, and habitat
loss beginning in the 20th century (Scarnecchia 1992; Buckmeier 2008; Buckmeier et al.
46
2017). Habitat loss and hydrologic changes (e.g., dams) have reduced or restricted
access to spawning floodplains (Mettee et al. 1996).
Alligator Gar is extirpated from much of its historic northern range in the
Mississippi River basin in Missouri, Illinois, Ohio, and Kentucky (Buckmeier 2008). For
example, Alligator Gar is designated extirpated in the Wabash River drainage in the
midwestern United States. The species was associated with the wetlands that surround
the Wabash River, but have not been collected there since the 19th century, likely due
to the draining of the wetlands beginning in the late 19th century (Simon 2006).
Individuals of the species have been reported outside their native range, but not
established, in South Carolina and California (Fuller 2019).
Relative abundance
There is a closed harvest on Alligator Gar in Florida because of limited data for
Florida populations; however, research on abundance and distribution is ongoing to
determine the appropriate status and management of Alligator Gar in Florida. Wegener
(2018) reports that less than 10 Alligator Gar have been captured in Pensacola Bay
rivers other than the Escambia but that 212 Alligator Gar were captured in the Escambia
River in 2015 (Wegener 2018). Research indicates that the estimated population in
Pensacola Bay drainages consists of at least 212 individuals with a calculated 95% C.I.
up to 328 individuals (Wegener 2018). While conducting a telemetry study in 2016 in
Pensacola Bay, Florida, no Alligator Gar was collected in the Yellow River, however,
personal observations recorded in Wegener (2018) note observations in the Yellow and
Blackwater Rivers. This might indicate a small, non-existent, or non-permanent
population in the Yellow River (Wegener 2018). Hoehn (1998) categorized Alligator Gar
47
in Florida as very rare and local throughout its native range (6-20 occurrences or less
than 10,000 individuals) or found locally in a restricted range. In this case, threatened is
defined (by FWS) as a species that may be relatively abundant but is subjected to
serious adverse pressures throughout their range (Hoehn 1998).
Of the 14 states where Alligator Gar were native historically, 6 now consider the
species to be rare or extirpated (Buckmeier 2008; Jelks et al. 2008). Populations are
facing declines due to habitat loss, overfishing, and impacts from historic removal efforts
(Scarnecchia 1992; Ferrara 2001; Buckmeier 2008; USFWS 2017). Alligator Gar has
been extirpated from Ohio and Illinois and is considered imperiled or critically imperiled
in Alabama, Arkansas, Indiana, Oklahoma, Kentucky, Mississippi, and Tennessee
(Brinkman 2003). Alligator Gar is considered vulnerable in Florida. It is estimated that
Alligator Gar populations have experienced a 30-70% decline from historic levels
throughout their native range (www.natureserve.org). However, populations are
considered robust in Texas and Louisiana (Brinkman 2003).
Studies suggest some populations are far below historic levels and continue to
decline, to the point of requiring reintroduction through stocking (USFWS 2016). The
American Fisheries Society identifies Alligator Gar as vulnerable (Hassan-Williams and
Bonner 2013) and numerous states are in the process of changing management and
conservation regulations as well as considering stocking (Buckmeier 2008; USFWS
2016).
Alligator Gar populations in the Vincente Guerrero Reservoir (Mexico) do not
appear vulnerable to overfishing, likely because fishing is confined to 7 months of the
48
year and harvest is biased towards males (Garcia de Leon et al. 2001). Populations in
Mexico support an active gill net fishery (Garcia de Leon et al. 2001).
Threats
Harvest has been a threat to Alligator Gar over long time periods. Native
Americans once used Alligator Gar scales as arrowheads, ornaments, tools, and
consumed Alligator Gar. Early settlers used Alligator Gar hides to cover wooden
plowshares in addition to consuming this fish (Scarnecchia 1992; Schultz 2004).
Alligator Gar and other “rough fish” were the targets of eradication efforts to improve
fishing for more desirable species (Scarnecchia 1992; Schultz 2004). Recreational and
commercial fishing still occur in some regions, though under more directed fisheries
management than in the past (Binion et al. 2015). Human impacts and predation by
alligators Alligator mississippiensis are listed as threats to Alligator Gar (Ross 2001).
Habitat alteration and loss have been major pressures on Alligator Gar
populations (Etnier and Starnes 1993). Dams have been constructed that limit
movement of this species (Etnier and Starnes 1993; Mettee et al. 1996). Stream
channelization, destruction of bottomland forests, separating floodplains from river
channels by constructing berms, and other alterations have negatively affected Alligator
Gar populations in some regions (Etnier and Starnes 1993).
Alligator Gar are vulnerable to overfishing despite their long lifespan and high
fecundity because of the low population numbers and late sexual maturity to a minimum
population doubling time of over 14 years (Froese and Pauly 2018).
If there are no length restrictions, Smith et al. (2017) estimate that harvest rates
of 6.5% a year would result in overharvesting of Alligator Gar. Males are thought to be
49
more vulnerable to harvest because they remain in the spawning area for extended
periods (Suttkus 1963; Garcia de Leon et al. 2001).
The small, isolated population of Florida’s Alligator Gar is a threat to the
population as the populations could easily be reduced or extirpated as a result of human
activity. While the harvest closure in Florida protects the species from fishing pressures,
the population is threatened by development. If there is a reduction or obstruction to
floodplain spawning grounds, the species cannot successfully reproduce.
Habitat and Movement
Physical (substrate, temperature, flow, depth)
Alligator Gar are demersal and inhabit large bays, rivers, swamps, bayous, lakes
and coastal marine waters (Lee 1980; Froese and Pauly 2018). Alligator Gar exhibit
preferences for weedy and shallow backwater sites with slow moving to moderate
currents (Kluender 2016) or oxbows, reservoirs, and brackish estuaries along the Gulf
of Mexico (Page and Burr 1991; Schultz 2004; Salnikov 2010; Allen et al. 2014;
Kluender 2016; Froese and Pauly 2018). Literature suggests that Alligator Gar
populations (e.g. brackish populations) in the eastern Gulf of Mexico rarely travel very
far upstream, primarily remaining in coastal streams along the northeast Gulf of Mexico
(Boschung and Mayden 2004; Buckmeier et al. 2013). Populations found in the
Mississippi are known to travel far upstream (Mettee et al. 1996; Boschung and Mayden
2004).
In Alabama they are commonly found over sand, gravel, silt, or mud (Mettee et
al. 1996). The maximum reported depth for Alligator Gar is 60 m (Gulf Base 2016).
Schultz (2004) notes that the species can survive hot, stagnant waters and they are
50
rarely found in brackish and marine waters (Page and Burr 1991). Ross (2001) reports
that Alligator Gar have the highest tolerance for saltwater of all gar species, they have
been observed in the Gulf of Mexico waters from Louisiana through Destin, Florida.
Alligator Gar is found in the Pensacola Bay System of Florida, which is a river
dominated system where freshwater flows influence salinity. The system encompasses
the Escambia River and Blackwater River where temperature ranges from 8℃ to 33.7℃,
averaging 22.2℃ (USEPA 2004). The pH for the system ranges from 4.1-9.1, with an
average of 7.8 (USEPA 2004). Hobbyist literature (www.numa.sk) notes that the
temperature can range from 15-32℃. The Warm Springs Hatchery uses filtered pond
and spring water to culture Alligator Gar (USFWS 2014). The water temperatures are
gradually increased through the production season by blending spring and pond water
to increase temperatures from 21℃ in May to near 28℃ in July (USFWS 2014).
Alligator Gar has a wide geographic range that encompasses 44-20° N and 101-80° W,
in the northernmost native range has temperatures have been reported as low as 1℃
and recorded highs of the native range have been 30℃ (Salnikov 2010). Fernando et al.
(2015) proposed that thermal tolerance may vary among Alligator Gar populations due
to local adaptations. Juvenile Alligator Gar from three populations in the Mississippi
River were studied at temperatures of 25-35℃ for thermal tolerance consistency and
critical thermal maximum tolerance among populations (Fernando et al. 2015). Results
demonstrated consistency of thermal tolerance among populations, with individual
critical thermal maximums ranging from 39.2-44.7℃ (Fernando et al. 2015).
General (terrestrial, estuarine, marine, freshwater)
51
While Alligator Gar is a freshwater species more commonly found in fresh than
brackish or saltwater (Froese and Pauly 2018), Suttkus (1963) notes that the species
(under L. spatula) is considered a common inhabitant of brackish water in Louisiana.
Suttkus (1963) discusses that multiple specimens have been found from in the Gulf of
Mexico, on the Gulf side of Breton Island and Grand Isle, Louisiana, and at Destin,
Florida. In Texas, Alligator Gar is routinely captured in estuarine habitats with salinities
over 20 ppt (Buckmeier 2008).
Alligator Gar is the most saline tolerant of all gar species; however, they only
spawn in freshwater (Mettee et al. 1996; Boschung and Mayden 2004). It has been
observed that larval Alligator Gar cannot tolerate salinities higher than 8 ppt; however,
adults can thrive in seawater up to 35 ppt (Suchy 2009; Green et al. 2015). Juveniles
under one year can tolerate salinity of 24 ppt for 30 days but show reduced growth
attributed to decreased appetite (Schwarz and Allen 2013).
Alligator Gar larvae over 40 DPH (Days Post Hatch) can survive salinities up to
18 ppt (Green et al. 2015). Based on LC50 dose response values, salinity tolerance of
larval Alligator Gar increased in stages, with the first increase occurring at 10 DPH and
another increase at 25-30 days post hatch (Green et al. 2015). Observed biomarkers for
ion analysis and NKA activity and noted changes as acute salinity tolerance increased
again from 15 to 40 DPH (Green et al. 2015). Based on salinity tolerance development,
Green et al. (2015) proposed a developmental response to salinity that is conserved
among coastal and inland populations.
Chemical (pH, salinity, dissolved oxygen)
52
Alligator Gar are a freshwater fish with adults exhibiting a high tolerance to
salinity levels. Alligator Gar larvae cannot tolerate salinity over 8 ppt; however, adults
can tolerate salinity levels over 35 ppt (Buckmeier et al. 2008; Suchy 2009; Green et al.
2015; Daugherty et al. 2017a). Gars can also tolerate a range in pH and water hardness
levels and their highly vascular air bladder enables them to thrive in a low dissolved
oxygen environment by taking in air at the surface (Schultz 2004). Hobbyist literature
(www.numa.sk) notes the preferred pH range is 6-8, hardness 90-450 ppm, and that
filtration is a big concern in aquaria due to the meaty, high protein diet, and waste
levels.
Alligator Gar is found in the Pensacola Bay System of Florida, which is a river
dominated system where freshwater flows influence salinity. The system encompasses
the Escambia River and Blackwater River. The pH for the system ranges from 4.1-9.1,
with an average of 7.8 (USEPA 2004).
Warm Springs Hatchery uses filtered pond and spring water to culture Alligator
Gar (USFWS 2014). The constant temperature of the water was buffered to an alkalinity
of at least 51 and a hardness of 83 ppm. Fluidized high calcium content limestone was
utilized in the buffering system to keep pH between 6.5 and 7.
Biological (plant cover, species associations)
Alligator Gar spawns annually if seasonal flooding conditions are met (Schultz
2004). Spawning is associated with floodplain habitats or flooded and submerged,
shallow, and weedy areas (Page and Burr 1991; Schultz 2004; Salnikov 2010; Froese
and Pauly 2018). The optimal substrate for spawning is herbaceous wetlands; however,
53
woody debris and scrub bushes are also suitable (Buckmeier et al. 2017; Most and
Hudson 2018).
Habitat Movement and Use
During cold months (December-March), Florida Alligator Gar show strong site
fidelity to off-channel habitats and travel less frequently than in warm months (April-
November) (Wegener et al. 2017). As temperatures become warmer, Alligator Gar
relocate into the main channel and aggregations disperse (Brinkman 2003; Kluender
2016; Wegener et al. 2017). Previous telemetry projects in Pensacola Bay (2016)
showed seasonal variation in habitat use (Wegener 2018). Bay habitats were used
more frequently than river habitats in colder months (December-April) and use of river
habitats increased from May to October (Wegener 2018). It is proposed that the habitat
shifts are due to thermal refuge or changes in food availability (Wegener 2018). There
are indications that Alligator Gar in the Escambia River use off-channel habitats and
move less in the winter than warmer seasons (May-October), while they use both main
and off channel habitats in the warm season (Wegener et al. 2017).
Alligator Gar are capable of long-distance migration but have been observed to
have a small home range. Buckmeier et al. (2013) suggest that estuarine Alligator Gar
do not move far upriver. Throughout the year, the linear home range for Alligator Gar in
Pensacola Bay averaged 41.32 km and ranged from 0.89-101.58 km (Wegener et al.
2017). Wegener also notes that the linear home ranges and rate of travel for Alligator
Gar differed between seasons.
Telemetry studies in the Alligator Gar’s native range has provided insights into
movement and habitat use. These studies provide insights into how habitat loss and
54
alterations can impact Alligator Gar. In Alabama, the greatest recorded distance for
Alligator Gar movement is 10.2 km, while the average daily travel is 1.56 km (Boschung
and Mayden 2004). In Texas, tagged individuals were observed to have a linear home
range of less than 60 km; however, several individuals have a home range over 100 km
(Buckmeier et al. 2013). Sakaris et al. (2003) and Brinkman (2003) discuss the linear
home range of Alligator Gar to vary from 6.57-16.7 km and the mean areal home range
was 1170 ha; these data indicate that adult Alligator Gar exhibit large home ranges and
are highly mobile. Alligator Gar in Florida exhibit similar large home ranges and high
mobility in warmer weather (Wegener et al. 2017).
Irwin et al. (2001) and Sakaris et al. (2003) suggest that larger Alligator Gar
move more than smaller individuals but found no seasonal effects on movement rates in
the Mobile-Tensaw Delta (Alabama). High catch rates (Irwin et al. 2001) and multiple
recaptures (Sakaris et al 2003) for small Alligator Gar suggests site fidelity is more likely
for juvenile Alligator Gar. In their native range, dams have limited access and movement
to spawning floodplains (Mettee et al. 1996) which has altered habitat use and
movement as well as spawning patterns and success.
In the winter, Alligator Gar are found in deeper waters, as evidenced by trawl
nets pulling up Alligator Gar from deep holes and estuaries in Louisiana (Suttkus 1963).
In the summer months, Alligator Gar frequent the surface and are known to exhibit a
rolling behavior at the surface, especially in the late summer months when temperatures
rise, and dissolved oxygen levels drop (Mettee et al. 1996).
Seasonal movement patterns may be a result of resource partitioning among
individual Alligator Gar and are similar to other piscivorous ambush predators
55
(Buckmeier et al. 2013; Solomon et al. 2013). In site fidelity and movement
experiments, Alligator Gar exhibited a range of high site fidelity, long distance
movement, and a combination of both characteristics (Allen et al. 2014). Thirteen
Alligator Gar exhibited site fidelity throughout a study in the St. Catherine Creek
(floodplain connected to the lower Mississippi River) whereas five Alligator Gar showed
highly variable movement patterns (Solomon et al. 2013). Alligator Gar that exhibited
site fidelity occupied small areas ranging from 4.8-12.9 ha while the variable group
exhibited an average range of 11.8 ha (Solomon et al. 2013).
Introduced range
No known populations of Alligator Gar exist outside of the historic native range
despite the occurrence of individuals collected in other U.S. states and in Asia.
Florida has a single record of Alligator Gar outside its native range in Pellicer Creek,
near to the coast in Flagler County, Florida from January 1970 (Fuller 2019). There are
no known established non-native populations of Alligator Gar in Florida.
The U.S. Geological Survey Alligator Gar species profile state list of non-
indigenous occurrences reports one Alligator Gar removed from Lake Wateree in
Fairfield, South Carolina in 2010. The status of Alligator Gar in the lake and nearby
Catawba River is reported as unknown; however, this is the only report of occurrences
in South Carolina noted by USGS (Fuller 2019).
The California Department of Fish and Game (now known as the Department of
Fish and Wildlife) recorded an individual Alligator Gar in the San Joaquin Delta,
California in September 1991 (Raquel 1992). The individual collected was 145.5 cm in
total length, 59 cm girth, and weighed 18.6 kg. The record states that the most likely
56
method of introduction was aquarium release and it has been recorded as failed to
establish in the area (Raquel 1992). The temperature and salinity at the point of capture
was 25℃ and 4.5 ppt, respectively. The most recent recorded observation of Alligator
Gar in California was in 2013; an individual Alligator Gar was collected from Lincoln
Park Lake in Los Angeles (Fuller 2019). The status of this introduction is considered
unknown. The introduction vector for this individual is thought to be aquarium release
(Fuller 2019). Similar to Florida, no verified non-native populations are known to exist in
California.
There are two reports of non-indigenous occurrences of Alligator Gar in Texas, in
2015 and 2016, both stocked for sport (Fuller 2019). Alligator Gar was introduced into
Lake Fairfield, Freestone Texas, in 2015 by the Texas Parks and Wildlife Department.
USGS (Fuller 2019) and Texas Parks and Wildlife Department (2018) report that 146
juvenile Alligator Gar were stocked for sport in an HUC of the Lower Trinity River, Lake
Fairfield, an area just outside of the historic native range. The status of the population in
Lake Fairfield is considered unknown (Fuller 2019). In 2016, three individuals were
collected with gill nets from Gonzales Reservoir, in Gonzales County, Texas over a 10-
night sampling effort (Binion 2016). Binion did not list the Alligator Gar in the stocking
history of the Gonzales Reservoir; however, Texas Parks and Wildlife Department and
USGS (Fuller 2019) note that the species is established in the area.
Alligator Gar is a valuable ornamental and non-native sport fish in Southeast
Asia. In 2009 an article titled “Monster exotic fish found in Hong Kong ponds”
(https://news.abs-cbn.com) reported that at least 16 Alligator Gar were removed from
retention ponds in a Hong Kong park. One of the individuals removed from the ponds
57
was one meter long. In Malaysia, Alligator Gar is one of the 24 introduced freshwater
species, most introduced for aquaculture, with a few from aquaria or sport (Chong et el.
2010). Chong found reports of the species being released by pet owners in Malaysia
concerning; however, they note that “there had been no serious attempt to list the
Alligator Gar as an introduced species nor to identify threats they posed” and there has
been no data collected concerning reports of introduction. FishBase (Froese and Pauly
2018) reports 4 records of occurrence in Thailand. The individuals collected ranged
from 85-116 cm; however, occurrence records are undated (Database of IGFA angling
records until 2009). The occurrences in Thailand are likely the result of stocked ponds
for sport fishing. USGS (Fuller 2019) reported a collection of a single Alligator Gar in
Meulaboh, Indonesia in 2011.
An individual Alligator Gar was caught in Marivan Lake, Iran in 2015 (Fuller
2019). On November 2008, an Alligator Gar was caught by anglers in the southern
Caspian Sea near the coast of Turkmenistan (Salnikov 2010). Conditions in the Caspian
Sea and nearby water bodies are similar to the species environmental preferences
exhibited in the native range (Salnikov 2010), but the likelihood of reproduction may be
low because no other individuals were captured. Alligator Gar were first reported in Iraq
in September 2016; a single specimen was collected in the southern part of the Shatt al-
Arab River, at Om-al-Rasas Island during an ichthyologic survey using gillnets (Mutlak
and Faisal 2017). The individual was determined to be an immature male, 900 mm in
total length. Mutlak and Faisal (2017) suspect that the aquarium trade is responsible for
the introduction of the individual. There are no further records of Alligator Gar in either
region.
58
In 2017, Kawase et al. (2017) published a report of the current state of non-
native fishes in the Yodo River, the report involved a field study where the Alligator Gar
was reported for the first time in the Yodo River Basin, Japan.
Biology
Reproduction
Alligator Gar are oviparous and usually spawn from April to June, correlating with
seasonal flooding (Suttkus 1963; Allen et al. 2014). Spawning only occurs in freshwater
environments (Boschung and Mayden 2004; Kluender 2016). The species exhibits
external fertilization and no parental care (Mettee et al. 1996; Boschung and Mayden
2004). Ideal water temperature for spawning was reported to be 18-23℃ (Most and
Hudson 2018); however, Alligator Gar were observed to spawn at temperatures of 23-
26℃ in the lower Mississippi drainage (Allen et al. 2014). The minimum duration of
inundation for spawning and hatching is 5 days (Buckmeier et al. 2017), while the ideal
duration of inundation is 60 days (Most and Hudson 2018) with a water temperature
between 20-30℃ (Echelle and Riggs 1972).
It is thought that spawning occurs in flooded backwater areas, but the empirical
evidence for the necessity of flooded backwaters is lacking (Buckmeier 2008). Lateral
spawning migrations were observed in floodplain areas associated with increased river
stages and higher temperature (Buckmeier 2008). Spawning has been linked to
seasonal flooding, which can lead to infrequent successful recruitment (Buckmeier
2008). Female Alligator Gar lay relatively large (2.0 ± 0.7 mm; Clay et al. 2009)
adhesive dark green eggs at a depth of 0.3-1.3 m that adhere to vegetation or substrate
until they hatch (Shultz 2004; Buckmeier et al. 2017; Most and Hudson 2018). The
59
optimal substrate for spawning is herbaceous wetlands; however, woody debris and
scrub bushes are also suitable (Buckmeier et al. 2017; Most and Hudson 2018).
Spawning behavior is like other lepisosteids, where 1-4 males pursue a single
female into shallow water and fertilize the eggs with milt (Mettee et al. 1996; Clay et al.
2009). While spawning, Alligator Gar thrash at the surface with their tails while releasing
sperm and eggs. Once fertilized, eggs settle to the bottom and stick to substrate,
including aquatic vegetation, tree limbs, and other debris (Mettee et al. 1996). When
spawning is complete, Alligator Gar return to deeper water and hatching occurs after
48-72 hours of incubation (Mettee et al. 1996; Mendoza et al 2002a; Buckmeier et al.
2017).
Time of year
Alligator Gar spawns are reported in spring (Fuller 2019) and early summer
(April-June in the United States) in shallow bays and sloughs (Schultz 2004), which
coincides with seasonal flooding of swamps (Simon and Wallus 1990; Boschung and
Mayden 2004; Buckmeier 2008). Cook (1959) observed apparent spawning in late May
and notes that during spawning, gars strike the surface of the water and create
commotion (Ross 2001).
It is reported that Alligator Gar spawn in May in Oklahoma (Ross 2001) as well
as January to September in Oklahoma and Texas (Echelle and Riggs 1972). In
Alabama, Alligator Gar were observed by Mette et al. (1996) to spawn from late March
to early June. In northeast Mexico, Alligator Gar have been observed to spawn from
July to August (Garcia de Leon et al. 2001).
Minimum age
60
The minimum age of sexual maturity for female Alligator Gar is thought to be 11
years of age while the males are younger, reported sexually mature at 6 years of age
(Boschung and Mayden 2004; Salnikov 2010).
In Louisiana, the sexual maturity of coastal Alligator Gar populations is earlier
than commonly reported, with females spawning at 4-6 years, and males at 3 years
(Ferrara et al. 2015).
Volitional spawning of males and females at 4 years of age was observed after
undergoing a rapid change in osmotic environment and handling (Patterson et al. 2018).
These fish were originally from Louisiana stock but were kept under aquaculture
conditions.
Frequency
Frequency of spawning is thought to coincide with seasonal flooding (Suttkus
1963). Seasonal flooding generally corresponds with April to June in the southeastern
United States (Suttkus 1963; Allen et al. 2014). Literature suggests that Alligator Gar
are periodic strategists, spawning when requirements for freshwater flooding, inundation
period, and temperature are met (Boschung and Mayden 2004; Kluender 2016).
Fecundity
The fecundity of Alligator Gar correlates with size; absolute fecundity is reported
from 130,000-157,000 eggs per female and 4.1 eggs/g body weight; however, fecundity
is highly variable (Boschung and Mayden 2004; Buckmeier 2008, Salnikov 2010).
Early life history
Alligator gar hatch after 48-72 hours of incubation (Mendoza et al. 2002a;
Buckmeier et al. 2017). After hatching, larvae average 7 mm TL and use a terminal
61
adhesive disk on the snout to adhere to substrate (Clay et al. 2009). Newly hatched
larvae have a visible yolk sac and adhere to vegetation for five days (or 13.5mm TL)
while feeding endogenously on yolk sac contents (Mendoza et al. 2002a; Mendoza et
al. 2002b; Clay et al. 2009). Yolk absorption takes 5-10 days, after which gar larvae
disperse and do not exhibit a pronounced tendency to school (Simon and Wallus 1990).
While capable of swimming, larvae are not strong swimmers and if larvae are detached
from substrate they will sink unless actively swimming (Mettee et al. 1996; Ross 2001).
Simon and Wallus (1990) observed that post yolk sac larvae are 14.9-57.3 mm TL and
that fin rays are present in the median and pectoral fins by 14.9 mm TL.
The color pattern of 24 mm Alligator Gar was described by Simon and Wallus
(1990) as jet black dorsum with vivid white areas and a white mid dorsal stripe form the
tip of the snout to the dorsal fin (Boschung and Mayden 2004; Aguilera et al. 2011).
Juveniles are solitary and float at the surface like sticks, after the yolk is absorbed the
gar can rest motionlessly in a horizontal position at any depth (Simon and Wallus 1990;
Schultz 2004). Very young Alligator Gar have a prolonged notochord that the caudal fin
is attached to, the notochord extends into a fleshy posterior filament (Boschung and
Mayden 2004).
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Figure 3-10. Kentucky Department of Fish and Wildlife. Coloration of juvenile Alligator Gar. July 14, 2009. Source: Kentucky Department of Fish and Wildlife. 2019. Alligator Gar. Kentucky Department of Fish and Wildlife. https://fw.ky.gov/Fish/Pages/Alligator-Gar.aspx
At five to ten DPH larvae lose their suctorial disk (14.9 mm TL) and begin free
swimming and feeding on zooplankton and invertebrates (Simon and Wallus 1989;
Mendoza et al 2002a). The transitional stage when larvae obtain nourishment from the
yolk reserves and active predation is known as the lecitho-exotrophic feeding stage
(Mendoza et al. 2002b). Exogenous feeding begins between 12.5 and 22.5 mm TL
(Clay et al. 2009). Mendoza et al. (2002a) conducted histological studies that reveal that
the digestive tract is fully formed by 5 DPH, signaling the start of lecitho-exotrophic
feeding. Complete exogenous feeding beings at 22 mm TL (Mendoza et al. 2002b).
Juvenile alligator gars range in total length from 98.0 to 117.0 mm (Simon and Wallus
1990).
63
Juvenile gars have distinctive irregular black stripes on the ventral sides and a
whitish stripe bordered by dark lines extending from somewhat behind the origin of the
dorsal fin to the snout (Ross 2001; Aguilera et al. 2011).
Age and growth
Female Alligator Gar exhibit larger maximum size and age than males; most
literature indicates that females live an average of 50 years while males live an average
of 26 years (Ferrara 2001; Boschung and Mayden 2004; Roberts and Harrel 2006;
Salnikov 2010). Some primary literature indicates that Alligator Gar live over 50 years
(Buckmeier et al. 2016). Growth is rapid in the first years of life before slowing as they
age. By the first year of age Alligator Gar grow 25-30 cm (Salnikov 2010); it takes an
average of 10 years to grow to 1 m, and 30 or more to grow to 2 m (Buckmeier 2008).
Until 10 DPH, larvae grow 1.5 mm/day, after 10 DPH growth rate increases to 5.06
mm/day until a total length of 50 mm is reached, generally around 15 DPH (Mendoza et
al 2002a; Aguilera et al. 2011). By 30 DPH, the larvae are considered juveniles, they
average 130 mm total length and no longer exhibit a dorsal line (Mendoza et al 2002a).
The average Alligator Gar grows up to 2 m TL and 45 kg; however, Alligator Gar
have been reported up to 3 m TL and 160 kg (Suttkus 1963; Salnikov 2010). Personal
correspondence (S.F. Hildebreans, F.A. Cook 1959) describes a 3.7-meter Alligator Gar
caught in 1933 in Lake Washington, Mississippi (Ross 2001).
FishBase (Froese and Pauly 2018) estimates that resilience of the species is
very low, with a minimum population doubling time of more than 14 years due to late
sexual maturation. However, recent studies have indicated that coastal Alligator Gar in
Louisiana mature faster than literature suggests (Ferrara et al. 2015). Age of maturity
64
was determined from otoliths, inspection of gonads, and histological analysis from two
southern Louisiana coastal populations. Ferrara et al. (2015) observed that females
matured at 4-6 years but at slightly smaller sizes (1,100-1,400 mm TL) than inland
females (11-14 years; 1,500 mm TL). Coastal males were also observed to mature
earlier, at 3 years, but at similar sizes to inland Alligator Gar (1,000 mm TL; Ferrara et
al. 2015).
Diet
Six to eight days after hatching larvae begin the transitional lecitho-exotrophic
feeding stage, when larvae obtain nourishment from the yolk reserves and active
predation of zooplankton and invertebrates (Mendoza et al. 2002a; Mendoza et al.
2002b; Aguilera et al. 2011). Exogenous feeding begins between 12.5 and 22.5 mm TL
(Clay et al. 2009). Mendoza et al. (2002a) conducted histological studies that reveal that
the digestive tract is fully formed by 5 DAH, signaling the start of lecitho-exotrophic
feeding. Complete exogenous feeding beings at 22 mm TL (Mendoza et al. 2002b).
Alligator Gar are described as an ambush predator and a scavenger (Froese and
Pauly 2018). They predominantly eat forage fishes; however, birds, invertebrates, and
fishing tackle have been found in their stomachs (Buckmeier 2008). Prey size for
Alligator Gar is related to snout size (Mendoza et al. 2002b). While their diet varies
considerably, it tends towards piscivory as body size increases (Echelle and Riggs
1972).
The size and shape of the Alligator Gar body and head is ideal for quick, short
dashes and ambush feeding. Alligator Gar float motionless, often getting mistaken for
branches or logs, until the gar performs quick lateral head movements, swallowing prey
65
whole (Mettee et al. 1996; Boschung and Mayden 2004). Brackish water Alligator Gar
have been known to feed on blue crabs as well as fish, invertebrates, sea birds and
other small mammals (Ross 2001; Froese and Pauly 2018). Studies have revealed that,
while Alligator Gar are infamous for eating anything, most of their diet consists of
Gizzard Shad Dorosoma cepedianum, Threadfin Shad D. petenense, Golden Shiners
Notemigonus crysoleucas, and rough or coarse fish species (Schultz 2004). FishBase
(Froese and Pauly 2018) notes that the trophic level is 4.0 (± 0.67) based on food items,
indicating a tertiary consumer.
Parasites and disease
The species is not susceptible to OIE reportable diseases (www.oie.int). Alligator
Gar are susceptible to pathogens including; Cestoda Proteocephalus ambloplitis,
Trematoda Clinostomum and Rhipidocotyle Lepisostei, Nemata Contracaecum
spiculigerum and Dechelyne lepisosteus (Wardle 1990; Mayberry et al. 2000),
Crustacea Ergalis versicolor (Hoffman 1967; Hassan-Williams and Bonner 2013), and
Macroderoides texanus in Texas (Tkach et al. 2008). There is no indication in literature
that these parasites are of concern in Florida (FDACS 2019b).
Control
Methods
Eradication efforts (e.g. dynamite and trapping; Scarnecchia 1992) and
overfishing have been effective in reducing Alligator Gar populations in their native
habitat (Buckmeier 2008). Alligator Gar spawning aggregations have been used to
facilitate eradication efforts in the past (Scarnecchia 1992).
Controlling populations of Alligator Gar would be possible through harvesting, as
harvesting over 6.5% of the population annually is estimated to be unsustainable (Smith
66
et al. 2017). Gill nets are commonly used by fishermen and scientists to collect Alligator
Gar in Mexico (Garcia de Leon et al. 2001) and the United States.
Case studies
Mutlak et al. (2017) states that there is no published information on the
establishment of Alligator Gar outside of their native range. Thus, there are no case
studies documenting the control of Alligator Gar.
While there are no case studies, there is some primary literature on eradication
efforts to cull gar, including Alligator Gar, populations. Scarnecchia (1992) notes that
methods include dynamite, particularly when the fish are congregated for spawning,
was highly successful. Johnston (1961) was quoted “During one day's operation, over
3.5 tons of gar were removed.” Burr (1931) developed early methodology for eradicating
gar through electrocution, after being shocked the gars would sink to the bottom and
drown. Gar trapping devices that took advantage of the gar’s size and reduced flexion
were used to trap and remove gar from river systems as well (Scarnecchia 1992).
Potential Florida Distribution
Hospitable Habitat
Florida has seemingly suitable habitat in coastal river systems along the northern
Gulf of Mexico coast east of the current range of Alligator Gar, including the Suwannee
River in Florida’s Big Bend. Many of these systems periodically flood surrounding
hardwood forest, backwaters, and coastal marshes (SRWMD 2017), presumably
suitable spawning and nursery habitat for Alligator Gar. Coastal rivers along the west
coast of Florida likely vary in habitat quality for Alligator Gar, particularly in spawning
and nursery habitat. With some exceptions, such as possibly the Peace River, most
systems have relatively small floodplains and short periods of floodplain inundation.
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Southern Florida has extensive wetlands that may prove suitable if Alligator Gar
is capable of using canals, solution holes, and sloughs as refuge habitat during low
water periods and successfully spawning and recruiting during high waters in flooded
marsh habitat.
East coast habitats may prove suitable for Alligator Gar survival but have
relatively few potential spawning/nursery areas. Inland areas of the Kissimmee River-
Lake Okeechobee system and the St. Johns River basin may have considerable
suitable habitat depending on the ability of Alligator Gar to successfully spawn and
recruit in more lentic systems. The Longnose Gar is a lotic spawner and successfully
spawns and recruits in both systems (Holloway 1954; Gandy et al. 2012). However, this
species spawns in channels rather than backwaters (Johnson and Noltie 1996).
Timing of flooding may be important, though Alligator Gar has an extended
spawning period across its native range (January to September depending on region;
Time of Year, above).
Climate matching (CLIMATCH, Australian Bureau of Agricultural and Resource
Economics) of the native range of Alligator Gar and the risk assessment area of Florida
shows a high climate match with a climate 6 score (Bomford et al. fish climate match
paper) of 0.920 (Hill, unpublished data; Figures 3-11; 3-12). Suitable climate occurs
throughout nearly all of Florida though the highest match occurs in the panhandle and
northern Florida (Figure 3-12). Eastern Florida has a higher match than western or
south Florida, with west-central Florida having the lowest match (Figure 3-12). The
climate stations in the western panhandle with a similarity value of 10 are climate
stations within the current Alligator Gar range (Figure 3-12). The climate matching
68
completed by the USFWS using RAMP is similar, though the pattern of highest match
differs with higher match in portions of southwest and central Florida and lower match
on the east coast (Figure 3-13).
Figure 3-11. Alligator Gar CLIMATCH source map (Hill, unpublished data).
69
Figure 3-12. Alligator Gar CLIMATCH target map in Florida (Hill, unpublished data).
Figure 3-13. RAMP (Sanders et al. 2014) map of climate match for Alligator Gar in the United States (USFWS 2017).
70
The Fish and Wildlife Service performed a climate match (Figure 3-13) for the
contiguous United States resulting in a Climate 6 score of 0.328 (scores >0.103 are
classified high) indicating a high climate match for the United States (USFWS 2017).
The climate match was high in the southeastern U.S., including peninsular Florida and
Texas. The climate match was performed with RAMP, a system that utilizes specific
weather stations as sources for the climate match (Figure 3-14; USFWS 2017).
Figure 3-14. RAMP (Sanders et al. 2014) interpolated grid based on weather stations showing spots for climate locations estimated based on grid, climate locations estimated (red) and non-source locations (gray) for A. spatula climate matching (USFWS 2017).
The northern most native range of the Alligator Gar has reported temperatures as
low as 1℃ and recorded highs of 30℃ (Salnikov 2010). Florida Springs average 22℃
year-round, well within the recorded thermal preferences for Alligator Gar. The Gulf
Coast of Florida has reported temperatures of 13℃ in January and 31℃ in August
(https://www.nodc.noaa.gov/dsdt/cwtg/all_meanT.html).
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Ecologically similar species
Florida Gar, Spotted Gar, and Longnose Gar are also large-bodied, piscivorous
fish that share habitat and food preferences with Alligator Gar. However, Alligator Gar is
much larger as an adult than these three species. Spotted Gar and Longnose Gar
naturally co-occur with Alligator Gar (Wegener 2018). Other relatively large piscivorous
fish that inhabit Florida and would likely interact with Alligator Gar if this species were to
establish within the state include Largemouth Bass Micropterus salmoides, Bowfin Amia
calva, Flathead Catfish Pylodictis olivaris, Channel Catfish Ictalurus punctatus, and Blue
Catfish I. furcatus, plus some large euryhaline species such as Atlantic Tarpon
Megalops atlanticus and Common Snook Centropomus undecimalis. All these species
naturally overlap with Alligator Gar somewhere within its native range.
Although Alligator Gar would overlap in habitat use with all these species to a
certain extent, all these species also occur in habitats that would generally lack Alligator
Gar. Potential for competition among these species would hinge not only on the shared
use of prey resources, but the limiting nature of these resources and their depletion
dynamics.
Introduction pathways
The most common introduction pathways for Alligator Gar in the literature are
aquarium release and deliberate release as a sport fish (USGS NAS 2019).
Release from captive populations
There is no commercial production of Alligator Gar in Florida; however, there is a
research population at the University of Florida/IFAS Tropical Aquaculture Laboratory in
Ruskin. These fish are held under permit and the facility is permitted by the Division of
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Aquaculture, Florida Department of Agriculture and Consumer Services (FDACS 2019)
for containment of conditional, non-native species. The facility operates under
mandatory Best Management Practices (BMPs) that includes provisions for containment
of conditional and non-native species (FDACS 2019). The facility is regularly inspected
for BMP compliance by FDACS. A recent evaluation of the Florida Aquaculture BMPs,
including the facility holding Alligator Gar, showed effective enforcement and high levels
of compliance with the conditional and non-native species provisions of the BMPs
(Tuckett et al. 2016).
If commercial aquaculture were allowed in Florida, all producers of Alligator Gar
would be certified by FDACS and would have to follow mandatory Florida Aquaculture
BMPs. This program is designed, in part, to reduce the potential for escape of
aquaculture stocks into the environment. Specific risk-mitigating practices can be
incorporated into the BMPs or culture regulations for conditional species (e.g., Lates
regulations; Hardin and Hill 2012).
Release of Alligator Gar into Florida as a sport fish is illegal without a permit from
the Florida Fish and Wildlife Conservation Commission (Florida Administrative Code:
Chapter 68-5).
In the United States, aquarium release is a primary vector of introduction of non-
native fishes. Aquarium release is cited as the most likely vector of individuals found
outside of their native range, second is stocking. The large size of Alligator Gar (2-3 m)
is likely the motivation for aquarium release as they quickly outgrow aquaria (i.e.
tankbuster; Holmberg et al. 2015). In Florida, the single reported introduction was
thought to have been an aquarium release (Fuller 2019). Under current regulations it is
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illegal for the general public to possess Alligator Gar as an ornamental species (Florida
Administrative Code: 68A-27.005).
Direct importation
There is no federal regulation prohibiting direct importation of Alligator Gar into
the United States and the species is cultured on fish farms in Asia. Importation,
possession, and sale of Alligator Gar in Florida is currently restricted and allowed only
under permit from FWC (FWC 2019b; Florida Administrative Code: 68A-27.005).
Incidental importation
There is no evidence of incidental importation of Alligator Gar. It is unlikely to be
confused with other gar because juvenile and adult Alligator Gar are distinctive, and
trade is restricted.
Range extension
There is no evidence of range extension for the Alligator Gar. While it has been
reported and collected in multiple countries outside of its native range, there is no
evidence of establishment outside of their native range
Potential Impact
Ecological
Potential to eliminate or significantly reduce native species
Although gar have long been thought to represent a threat to more desirable native
species, thinking has shifted considerably in recent decades to a more balanced stance
which views gar more similarly to other species in fish communities (Scarnecchia 1992).
Alligator Gar naturally overlaps in range with the predatory fishes it would encounter if it
were to establish in other regions of Florida. Food competition might occur but the
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effects of competition, if any, would hinge on the use of the resource, its limiting nature,
and its depletion/production dynamics.
Predation on native fishes and other organisms may be a concern for such a
large-bodied predator. Non-native Flathead Catfish has had large predatory impacts on
the abundance of Redbreast Sunfish Lepomis auratus and two bullhead catfishes
Ameiurus spp. in Florida (Dobbins et al. 2012). Concerns over predation by the large-
bodied Barramundi Perch Lates calcarifer contributed to a high-risk score for
environmental impacts in a Florida risk assessment (Hardin and Hill 2012).
Nevertheless, the potential impacts of Alligator Gar on prey populations are less clear.
No populations of established, non-native Alligator Gar exist to determine if impacts
have occurred. The few studies of re-introduced Alligator Gar suggest little evidence of
competition or prey depletion. For example, diet studies in a re-introduced population in
western Kentucky suggests opportunistic feeding behavior and a lack of diversity in
abundant prey for four sympatric gar species (Richardson 2015).
There are concerns that hybridization with native gar species (Spotted Gar and
Longnose Gar) or between cultured and native Alligator Gar, may result in negative
impacts and loss of adaptations of the native species currently within its native range.
Bohn et al. (2017) has documented hybridization between Alligator Gar and Longnose
Gar in the wild. Research suggests that the large size of female Alligator Gar make
them attractive to other native gar species, potentially resulting in loss of genetic
diversity and adapted traits specific to coastal or inland individuals (Wegener 2018). In
aquaculture, fish from different sources (e.g. coastal vs inland) are recommended to be
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separated reproductively by behavior as the estuarine (coastal) fish do not move far
upriver (Buckmeier et al. 2013; Fernando et al. 2015).
Studies that are ongoing in Florida to assess if hybridization has occurred in
Pensacola Bay, Florida, between these species (Wegener 2018). Hybridization between
Alligator Gar and Longnose Gar has been documented in captivity and the wild
(Herrington et al. 2011; Bohn et al. 2017). Potential risks of hybridization if the Alligator
Gar were to establish in other regions of Florida would increase if the species would be
more likely to hybridize within the new range. Of the two species that have hybridized
with Alligator Gar in their native range, Spotted Gar does not occur naturally in Florida.
It is not known if the most common gar in the state, Florida Gar, can hybridize with
Alligator Gar.
History of range extension, high population growth rate, tendency to monoculture
Alligator Gar exhibit low population growth rates and the estimated population
doubling rate is over 14 years (Froese and Pauly 2018) due to the late maturation of the
species.
While there are Alligator Gar reported outside of the United States, there is no published
information on Alligator Gar establishing populations outside of North America (Mutlak
et al. 2017).
Alligator Gar exhibit no tendency to monoculture; adults can be found in small
aggregations, as evidenced by the success of the use of the Judas technique to locate
untagged adults in Alligator Gar telemetry studies (Wegener 2018); however,
aggregations disperse during warmer seasons (Brinkman 2003; Wegener et al. 2017).
Potential to adversely impact listed species
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Florida has few imperiled species that are likely to interact with Alligator Gar if
this species were to establish populations outside its native range in Florida. Many listed
fish species naturally overlap in range with Alligator Gar (e.g. Gulf Sturgeon Acipenser
oxyrhynchus desotoi; Blackmouth Shiner Notropis melanostomus, Saltmarsh
Topminnow Fundulus jenkinsi).
Potential for habitat alteration
Alligator Gar are not known to alter habitats directly or indirectly.
Human Impact
Despite the intimidating size and sharp teeth of the Alligator Gar, there are no
records of the Alligator Gar negatively impacting human health. Fishbase (Froese and
Pauly 2018) lists the Alligator Gar as harmless to human health. There are no
documented attacks on humans and observations indicate that when disturbed by
fishermen or swimmers, Alligator Gar swim deeper and away from contact (Suttkus
1963).
Alligator Gar meat is safe for human consumption; however, the eggs are toxic if
ingested by mammals, reptiles, and crustaceans (Boschung and Mayden 2004;
Broussard 2009). While Alligator Gar are not known for presenting a danger to humans,
handling them can result in injury due to their sharp teeth and head plates (Mettee et al.
1996). It is noted that Alligator Gar have potential to damage boats and fishing gear due
to their large size and teeth (Scarnecchia 1992).
Economic
Biofouling
No evidence of biofouling in native range.
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Competition with agriculture/cultured crops
No evidence of competition with agriculture or cultured crops.
Impact agriculture/cultured crops
No evidence of impacts to agriculture or cultured crops.
Socio-economic impacts
Positive socio-economic impacts of Alligator Gar result from ornamental sales
through the aquaculture industry and the increased interest and market as a sportfish
and for food. In Alabama and in the Rio Grande River there is a thriving recreational
bow fishery for Alligator Gar (www.fws.gov). In Texas there is the belief that angling
activity for Alligator Gar has increased (Buckmeier 2008). Guided gar fishing trips are
valued up to $750 a day (www.reeis.usda.gov) and Alligator Gar meat is sold in the
French market in New Orleans, the southern United States (valued at $3/pound in
Arkansas), and Mexico (Suttkus 1963; Garcia de Leon et al. 2001; Buckmeier 2008).
Alabama Game and Fish Division also note a growing demand for Alligator Gar meat in
the southeastern United States which has resulted in increased commercial fishing
(Mettee et al. 1996).
The impact of Alligator Gar to sportfish is negligible. In Texas, Alligator Gar have
been found to benefit healthy sportfish populations by eating weaker fishes, increasing
growth rates and stock health. In Texas, it was noted that lakes great for sportfishing
have healthy Alligator Gar populations (Felterman 2015; https://tpwd.texas.gov).
The negative social perceptions of the species as a monster fish may result in
management and removal costs if the species was to establish outside of its native
range and was perceived to be a threat to humans.
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Human Use
Aquaculture
Alligator Gar aquaculture has been successful due to the species high fecundity;
broodstock can easily be maintained, readily spawn in captivity, can tolerate poor water
quality, and can be reared entirely on an artificial diet (Weed 1923; Mendoza et al.
2002a; Mendoza et al. 2002b; Clay et al. 2009).
There is interest in Florida to culture Alligator Gar for food and out-of-state sale
for the aquarium trade; however, the activity is not currently permitted. Scarnecchia
(1992) notes "the flesh of gars is not only edible, but highly palatable… compares
favorably with the flesh of highly regarded game and food species." Biologists note
there is a growing interest in Alligator Gar overseas for sport (Fuller 2019).
There is potential for culture of Alligator Gar for conservation and restoration.
There are currently three federal fish hatcheries culturing and producing young Alligator
Gar to supplement wild populations; the Private John Allen National Fish Hatchery
(Tupelo, Mississippi); Tishomingo National Fish Hatchery (Tishomingo, Oklahoma); and
Aquaculture Center ‘Tancol’, Tampico, (Tampaulipas, Mexico) (Buckmeier 2008,
USFWS 2016). The Warm Springs National Hatchery is part of the restoration efforts for
the Mobile and Mississippi River drainage basins (USFWS 2014). The Natchitoches
National Fish Hatchery is working with the Private John Allen National Fish Hatchery
and Tennessee Wildlife Resource Agency to produce Alligator gar to aid in developing a
recreational fishery in west Tennessee (USFWS 2016).
Commercial value
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Alligator Gar are highly desired in the aquarium trade in Asia, the value of an 8
foot Alligator Gar is reported to be $40,000 in Japan
(https://www.courthousenews.com/a-strange-case-a-strange-fish/). In 2003, commercial
fisheries landings for gars in Louisiana (alligator gar, longnose gar, shortnose gar, and
spotted gar combined) was valued at greater than $515,000 (LDWF 2005). In 2007,
commercial anglers in Texas reported gar harvests of 1,000 lbs. or less (Buckmeier
2008). The average commercial harvest of alligator gar in Louisiana from 1999-2006
was 523,617 pounds/year and the 2003 commercial fisheries landings for gars (Alligator
Gar, Longnose Gar, Shortnose Gar, and Spotted Gar) was valued at greater than
$515,000 (LDWF 2005; DiBenedetto 2009). In Baton Rouge, Louisiana, at the local
seafood market, gar filets sell up to $3/pound (Buckmeier 2008; DiBenedetto 2009;
Zullo 2009). Guided gar fishing trips can cost up to $750 a day (www.reeis.usda.gov).
The Aquaculture Center Tancol in Tampico, Mexico is producing Alligator Gar for
food use (Buckmeier 2008). Suttkus (1963) writes that Alligator Gar meat is sold in the
French market in New Orleans and the southern United States. Alabama Game and
Fish Division note a growing demand for Alligator Gar meat in the southeastern United
States which has resulted in increased commercial fishing (Mettee et al. 1996). In
Florida, there is an interest in culturing Alligator Gar for food. Buckmeier (2008)
addresses an article titled “Gar in the Pan” that notes that Alligator Gar meat sells for
$3/pound in Arkansas and was more popular than catfish. The FAO notes that there is
aquaculture of Alligator Gar in Mexico, where it is highly valued as a food fish (Garcia
de Leon et al. 2001; Buckmeier 2008).
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Sport fishing for Alligator Gar has become popular in recent years in Louisiana,
Arkansas, Mississippi, and other states in the Mississippi Valley (Suttkus 1963), in
Alabama, Alligator Gar is a popular sport fish (Mettee et al. 1996). Mettee estimates that
several hundred gars (species not specified) are harvested annually in Alabama for
sport. In Alabama and in the Rio Grande River there is a recreational bow fishery for
Alligator Gar (www.fws.gov). In Texas, although there are no data to support it, there is
the belief that angling activity for Alligator Gar has increased (Buckmeier 2008).
Conservation and Restoration
Supplemental stocking has been proposed as a conservation measure to
supplement or reintroduce Alligator Gar within their native range (Barnett et al. 2011;
Perschbacher 2011). Precautions are taken in hatchery management to prevent mixing
broodstock from distinct populations and losing population adaptions as a result of
inbreeding (Fernando et al. 2015).
The Private John Allen National Fish Hatchery in Mississippi serves as the Fish
and Wildlife Service’s lead for restoring Alligator Gar in the Southeast United States by
providing juveniles for stocking efforts in Tennessee, Kentucky, Missouri, Kansas, and
Illinois (www.fws.gov). Warm Springs National Fish Hatchery in Georgia, in association
with hatchery services, provides continuing research in genetics, development of
intensive culture and production techniques, stocking support, and tagging/marking to
aid in Alligator Gar conservation efforts (USFWS 2016). The Tishomingo National Fish
Hatchery in Oklahoma set a record for Alligator Gar growth and production; the gars
were transferred to Missouri to be stocked for conservation (USFWS 2016).
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Research in Florida to provide better provide population estimates and
movement and habitat use is continuing to allow for better management regulation
reflective of the population status in the state. There has been research in tagging
individuals to better understand habitat use and movement, as well as better estimate
population size in Florida. In Florida, genetic studies to determine if genetic variation
events have occurred between gar species and Alligator Gar in the past.
Research
Current research encompasses federal and state agencies, universities, and
departments that study movement and habitat use, reproduction, biology, aquaculture,
and restoration efforts. Ongoing research efforts and facilities are noted on the Southern
Division American Fisheries Society Alligator Gar Technical Committee website
(https://units.fisheries.org/sdafsalligatorgarcommittee/research/).
Figure 3-15. Bar chart of Alligator Gar literature produced from 1990-2018. Photo courtesy of author (Web of Science).
Historic Use
Alligator Gar were used for meat and tools; the scales were used by Native
Americans for as arrowheads, jewelry, and other instruments. Gar skin was used for
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leather and by farmers to cover their wooden plowshares (Weed 1923; Scarnecchia
1992; Schultz 2004). Stuffed gars were noted in literature to be given as gifts (Boschung
and Mayden 2004; Salnikov 2010).
Social
Alligator Gar were historically viewed as “weeds and wolves among fishes” and
students were taught that gars made nuisances of themselves by becoming entangled
in nets. Under (repealed) Iowa statutes, it was not legal to release the gar alive
(Scarnecchia 1992). There is now a more positive perception of the species due to its
value as sport and food fish (Sutton 1998).
There has been positive publicity as possible means to control Asian carp;
Michigan Sea Grant writes that while the Alligator Gar is not the only solution, they
would likely take advantage of the abundance of carp in the Mississippi River and
Illinois River which would help reduce Asian Carp populations (MSU 2016). Other
articles titled “How to combat Asian carp? Get an Alligator Gar” (www.latimes.com) and
“Conservation of Ancient Fishes: Reintroducing the Alligator Gar; and What About
Those Carp?” (https://blog.nationalgeographic.org) briefly discuss the positive impacts.
While these articles do not discuss that Alligator Gar are not the only solution, they
reflect a more positive social view of Alligator Gar than historically seen.
In Hong Kong, Alligator Gar were reported in a public pond because park visitors
feared for their safety (https://news.abs-cbn.com). Individuals unaware of the Alligator
Gar’s diet may find the presence of Alligator Gar distressing, resulting in negative
publicity. A National Geographic article (https://www.nationalgeographic.com) describes
characteristics of Alligator Gar as “menacing looking behemoth” and “prehistoric mega
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fish with a tooth filled mouth and broad alligator like head”, which would be intimidating
to the public. The intimidating presence of the fish has been reinforced by popular
television shows such as “River Monsters” that had an episode on Alligator Gar. The
episode description describes the species as a “fish reputed to have committed a series
of violent attacks on humans, said to be as vicious as a shark and as big as a gator.”
The large size of the Alligator Gar can be intimidating, but Scarnecchia (1992)
attributes the large maximum size and distinctive characteristics to have helped the
Alligator Gar become more desirable as a trophy fish. Increased interest in angling for
Alligator Gar and better understanding of the role Alligator Gar provide in aquatic
ecosystems (Ross 2001) have resulted in efforts to actively manage and provide more
information on Alligator Gar populations and behavior.
Legal
In Florida, a closed harvest on Alligator Gar was enacted in 2006, making it
illegal to take or possess Alligator Gar without scientific permits (FWC 2019b).
Tennessee is restocking fish and does not allow harvest (Buckmeier 2008) and
Oklahoma has closed a known spawning area for fishing during spawning season.
Several additional states are stocking or considering stocking Alligator Gar.
Seven states have imposed fishing regulations that restrict or prohibit harvest
(Binion et al. 2015). Harvest regulations vary by state, bag limits are as follows:
Alabama (1/day); Arkansas (2/day); Florida (harvest prohibited), Mississippi (2/day);
Texas (1/day), and Oklahoma (1/day) (DiBeneditto 2009). The state of Louisiana has no
bag limit, size limit, commercial license limitations, or closed season regulations
(Ferrara 2001; DiBeneditto 2009).
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Conservation Status
In 2006 Florida Fish and Wildlife Conservation Commission (FWC 2019b)
implemented a harvest closure in response to limited data regarding native Alligator Gar
populations. It is also illegal in Florida to take or possess an Alligator Gar without a
permit. Florida Fish and Wildlife Conservation Commission will issue permits for
scientific research and management efforts (FWC 2019b).
Risk Screening
The mean FISK score for Alligator Gar was 4, with a low individual score of 3 and
a high score of 5 (Table 3-1). All scores are on the lower end of medium risk (non-
invasive) given a calibrated non-invasive/invasive threshold value of 10.25 for
peninsular Florida (Lawson et al. 2015).
Alligator Gar have no history of establishment outside of their native range and a
low average score for undesirable traits (Figure 3-17); if these characteristics are
present, they increase FISK score as they are traits of invasive species. The lack of
establishment, despite introduction, and few undesirable traits contribute to the lower
FISK risk level. Salinity tolerance (35 ppt; Suchy 2009; Green et al. 2015) and lack of
data for minimum population size to maintain a viable population are undesirable traits
that increase the FISK score. The lack of invasion history and undesirable traits
contributed to the mean score of 4 for the FISK risk screening of Alligator Gar
aquaculture in Florida.
The main factors that increased the score were high climate match, introduction
of individuals outside the native range, large body size, high salinity tolerance for
dispersal, ability to breathe air, potential for hybridization with native species, potential
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for humans to illegally stock this species, wide dispersal and movement of adults, and
resilient physiology (Table 3-2). Factors that decrease the overall score included the
lack of establishment history outside of the native range, lack of impacts in introduced
populations, lack of invasive relatives, lack of OIE-reportable pathogens, presentation of
no threat to human health, no parental care, and long generation time (Table 3-2).
Assessors indicated similar overall certainty levels, with assessor one at 0.79,
assessor two at 0.84, and assessor 3 at 0.75. The overall certainty level is computed by
the FISK software from certainty responses. The certainty level corresponds to the
confidence level that the assessor associated with the risk response (FISKv2 2013).
The confidence level is indicative of the level of certainty (or uncertainty; Copp et al.
2009), with the index ranging from a low of value 0.25 to a high value of 1 (Almeida et
al. 2013; Vilizzi and Copp 2013). Certainty can be influenced by the quality of literature
available, tool guidance, and the risk tolerance and experience of the assessors.
While overall certainty was similar for all three assessors, there was some
variation in certainty among all assessors over the 49 questions of the Alligator Gar
FISK risk screening (Figure 3-2). Assessor two had no ‘very uncertain’ classifications on
the overall risk assessment, while assessors one and three respectively had 2 and 3
responses marked as ‘very uncertain’. In the overall assessment, there were very few
responses among all three assessors that were marked as ‘very uncertain’. The highest
level of certainty (0.84) was associated with assessor two, who also had the highest
level of ‘very certain’ responses. Assessor three had the lowest overall certainty level
and exhibited the lowest number of ‘very certain’ responses for the risk screen, with
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18% fewer ‘very certain’ responses than assessor two and 10% fewer than assessor
one.
The review process did not change the mean scores and only a minor change
was made to the overall certainty of one assessor. There was a four-point difference in
the answers to both the biogeography and biology/ecology sections questions, with
persistence attributes having the most disagreement (five-point difference). The overall
certainty of the assessors was similar, with the least experienced assessor having the
lowest certainty. After review, this assessor adjusted the certainty upwards slightly
(+0.05). The justifications and responses of each assessor were generally in agreement
with only one unclear question response (6.05). The major differences in answers
stemmed from differing interpretation of the data. For example, Alligator Gar are air
breathers. Two assessors interpreted this as enough evidence for it to be able to
survive out of water, while one assessor did not (question 4.09). Answers to question
8.04, about the species benefiting from disturbance, differed as well. One assessor
provided flooding as a benefit while the other two provided dams as an impediment to
Alligator Gar spawning. Additionally, there was disagreement in responses to question
6.03 (about hybridization potential) based on the interpretation of the limited information
available about hybridization of this species. Incomplete data also affected the
responses to question 5.01 (about adverse foraging effects) with all assessors
answering differently with varying levels of uncertainty. Overall, the assessors and
reviewer agreed with the FISK results, with data deficiency and interpretation explaining
the differences in responses.
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The FISK risk screen score indicated that further, comprehensive risk
assessment needed to be performed to more accurately assess the risk of Alligator Gar
aquaculture in Florida.
Generic Analysis
Stakeholder Workshop and Generic Analysis
The stakeholder workshop was attended by eight of the eleven stakeholder panel
members. The stakeholder qualitative assessment utilized the biological synopsis, FISK
risk screenings, and the expertise of the stakeholder panel to perform the
comprehensive risk assessment suggested by the FISK risk screen. During the initial
discussion sessions prior to the qualitative assessment, the panel posed the question of
if there was enough expertise to be able to perform this assessment. Following
discussion, the panel concluded that the panel was trained and knowledgeable enough
to complete the Generic Analysis. The conclusion was reiterated in the post workshop
evaluation, where 100% of respondents felt the panel represented an appropriate
composition of expertise and backgrounds.
Breakout groups were utilized to facilitate initial discussion of questions regarding
the probability of establishment and the impacts of establishment. Breakout groups
were unable to come to a complete consensus on risk levels for consequences of
introduction or establishment, resulting in multiple risk levels and associated certainty.
Each breakout group resulted in an overall probability of introduction, consequences of
establishment, and overall risk potential. The average risk level for probability of
introduction was medium for group 1 and low-medium for group 2. The overall risk level
for consequences of establishment was the same for each respective group, both
groups averaging medium. The overall risk potential for each breakout group was
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medium, consistent with the overall group’s overall risk potential (ORP). Medium risk in
the Generic Analysis indicates that the organism is of moderate concern and that risk
mitigation is justified (ANSTF 1996).
The breakout groups gave consistent risk ratings for the presence in the pathway
and introduction, high risk, with varying certainty (Table 3-3). Group 1 was more certain
that Alligator Gar would be in the pathway while Group 2 had variation in certainty at the
extreme ends of each spectrum. Some members of Group 2 were very certain that
Alligator Gar would be in the pathway as there is are already an ornamental wholesale
pathway in Florida as well illegal sales. Colonization potential was also ranked similarly
between the groups, with medium or low-medium, but with similar low certainty (VU and
RU). Spread potential results differed among the groups despite the rating listed as the
same, medium. Group 1 had the highest variation (low and high) and somewhat less
certainty (RU and MC). The two groups differed slightly in the overall risk rating for
establishment, with Group 1 rating medium and Group 2 a low-medium.
There were greater differences in results for environmental impacts between the
two breakout groups, with Group 1 rating medium risk and Group 2 rating low and
medium for an overall low-medium (Table 3-3). Certainty also varied, ranging from VU
to RC. Economic impacts were rated similarly (M for Group 1 and L-M for Group 2) with
some variation in certainty. Group 1 rated the social/political impacts low (and VU) while
Group 2 ranked impacts higher (L-M and M), but with higher certainty (MC and RC).
The overall risk rating for impacts for both groups was medium. Combining the
averages of both groups ratings resulted in the same medium overall risk potential
outcome regardless of which group combinations were used.
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The group discussion largely mirrored the breakout groups, with slight
differences that suggested somewhat lower perceptions of risk, though certainty
remained the same or decreased slightly (Table 3-3). The group concluded that risk of
presence in the pathway and introduction risk were both high and, for this element,
certainty increased overall (RC and VC). The group ratings and certainty for
colonization were nearly identical to the results from the breakout groups (M), with a
slight increase in certainty. Spread risk was also similar among the overall group and
breakout groups at medium. The overall risk of establishment was the lowest of the four
ratings (L).
Environmental and economic risks were rated by the group as medium, with a
spread in ratings from low, low-medium, and medium with low certainty (RU) for
environmental impacts and higher certainty (MC) for economic impacts. The
social/political risk rating was low-medium, with a decline in overall certainty to
reasonably uncertain. The ORP, using medium for establishment and medium for
impacts/consequences, was medium. Medium indicates that Alligator Gar is of
moderate concern, and risk mitigation is recommended.
Several topics arose during the breakout groups and overall group discussion.
Topics important for establishment and spread included risks of introduction from the
pathways, reproductive requirements, the reproductive status of potential brackish water
populations, lack of establishment outside of the native range despite introductions, and
the lack of natural spread east and south beyond the western panhandle. Topics related
to the consequences of establishment were predation impacts directly on native species
and indirectly through competition for resources, hybridization with native gars, genetic
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interactions with native Alligator Gar, and potential economic impacts of control
programs for a cryptic species. Potential benefits of Alligator Gar culture were also
discussed, with economic benefits from culture and trade, increased biosecurity
resulting from decreased illegal trade and introduced diseases, potential to reduce
illegal trade, increased research of captive stocks, and increased awareness of an
imperiled, native species.
Some stakeholders expressed concern that a risk assessment was unnecessary
or counterproductive. Comments solicited from stakeholders after the workshop
addressed this point: “FWC’s webpage highlights the historic and declining range of
alligator gar and details the need for conservation of this species. Alligator gar is a
native species to Florida so a risk assessment to investigate the risk of colonization or
range expansion seems counterproductive when the species has not spread, and
considerable research and funds are being spent to conserve the species in Florida.
Aquaculture can provide valuable insight into the reproductive biology and habits of fish
to inform conservation efforts.”
During breakout and group discussions, the panel considered the risk of
introduction of Alligator Gar high. The certainty for this question was mostly moderate. A
discussion of risk mitigation took place at the end of the workshop, with panel member’s
opinions regarding the effectiveness of the Florida aquaculture BMPs as risk mitigation
solicited. The panel generally agreed that current regulations and practices were
sufficient to mitigate risk if containment, record keeping, and enforcement of these
practices were raised to be equivalent to species on the conditional, non-native species
list. During this conversation, concern was expressed again for potential internet pet
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sales that may be released in Florida, with the panel acknowledging that this was an
inevitable risk whether culture was permitted or not. Concerns for introduction in the St.
Johns watershed were noted, as there would be no barrier to prevent Alligator Gar
spreading north to Georgia. Appropriate site location for aquaculture facilities was
discussed to mitigate this concern.
The reproductive requirements of Alligator Gar and the Florida regions where
conditions would be suitable was a topic repeated throughout the workshop. Literature
provides little indication of the potential for Alligator Gar to spawn and recruit in other
aquatic habitats and high environmental specificity for successful spawning and
recruitment. The occurrence of rare volitional spawning of various gar species in
captivity as well as volitional spawning in earthen ponds (Patterson et al. 2018) led to
questions regarding the ability of Alligator Gar to spawn and recruit in the rivers, lakes,
and marsh systems that make up peninsular Florida. Additionally, frequent discussion
focused on the population of Alligator Gar that remain in brackish water bays and
marshes of the native range, that potentially spawn in tidal creeks or other areas with
freshwater inflow. Panel members speculated that these populations may be able to
spawn in estuarine conditions, however, little is known about the prevalence, biology, or
ecology of these populations, especially in Florida.
Several panel members noted the lack of successful invasion history of Alligator
Gar in discussion, particularly in reference to the lack of movement into peninsular
Florida. The native range of Alligator Gar extends south into Mexico, further highlighting
questions as to why Alligator Gar have not occupied similar latitudes in Florida. The
high salinity tolerance of adults and considerable migration and movement potential of
92
adults also made this discussion a highlight for future research and questions of
invasion potential. Habitats east of the current Alligator Gar distribution appear suitable
for the species, yet there is no evidence of the presence of Alligator Gar historically or
currently in the area beyond occasional sightings. The panel and project team are
unaware of any specific barrier that is preventing Alligator Gar from spreading naturally
east in the panhandle or south into peninsular Florida. This issue was important for
several panel members, who viewed this element as a telling characteristic of the
reduced potential for establishment outside of the native range in Florida.
Many panel members felt that predation impacts were medium risk in breakout
groups but changed the risk ranking to low or low-medium in the overall group
discussion, with some maintaining medium risk level. Alligator Gar is a large,
piscivorous predator, however, the panel noted that there was a lack of evidence for
clear predation or competition effects within the native range or where the species has
been re-introduced.
Hybridization was a primary concern and discussion point throughout the
workshop, with impacts to native gars, especially Longnose Gar a considerable concern
for some panel members. Some panel members consider this a minor issue, as
Alligator Gar in the panhandle coexist with Longnose Gar naturally. There was relatively
little concern from the panel for potential genetic exchange between wild and cultured
Alligator Gar, but this risk was not unimportant. One panel member discussed that
suspected hybrids had been found in Florida, and that genetic samples were collected.
There is currently no evidence to confirm hybridization in Florida. This concern is not
more alarming due to the common practice of stock enhancement and reintroduction
93
programs by federal and state agencies in many parts of the historic native range of
Alligator Gar (e.g. Texas, Illinois, Kentucky).
The primary economic cost associated with establishment of Alligator Gar
discussed by the panel was potential control costs. There was some disagreement
among the panel if the state (FWC) would attempt to control the species and, if so, what
the cost of control would be. It was noted that while Alligator Gar are large, they can be
cryptic in a large system, increasing the control costs as they would be more difficult to
find, capture, and remove. The preliminary difficulties encountered by researchers in
Florida finding and collecting Alligator Gar was discussed in support of the difficulty,
time, and cost that would be associated with removal efforts. The panel agreed that
costs could be high, upwards of $1,000,000 should control efforts be attempted for a
large, interconnected system. Social impacts of the release of a large, predatory fish
were also connected to higher control costs. Social impacts were also observed to be
low by some panel members, as Alligator Gar are not highly visible in large systems,
reducing the social impacts. Conversely, several panel members noted that controlling
populations through increased harvest pressure would likely result in reduced potential
economic costs as Alligator Gar appear highly susceptible to exploitation.
The direct and indirect benefits of permitting commercial Alligator Gar culture
included economic gains accrued by individual fish farms and the aquaculture industry.
Industry representatives stated that only five to six ornamental farms have the technical
ability and space to raise Alligator Gar for ornamental trade, with even fewer (two to
three) interested in culturing them until the market was more developed. The sale of
Alligator Gar would likely be profitable for ornamental farms, with more time needed to
94
develop broodstock, saleable inventory, and markets for food production of Alligator
Gar. Other potential benefits to the state include a large, easily obtained supply of
juvenile Alligator Gar for stock enhancement or reintroduction programs as well as
considerable research on the reproduction and behavior of Alligator Gar in captivity.
Additionally, stakeholders commented that the increased presence of Alligator Gar in
trade and on local farms may increase awareness of an imperiled, native species, and
provide an example of a native fish in aquaculture.
Alligator Gar are currently produced on farms in Southeast Asia (personal
communication Craig Watson, University of Florida) and shipped live to consumers. A
legal, healthy, and inspected stock of ornamental Alligator Gar in Florida may replace
this trade and would improve biosecurity for cultured fishes as well as wild stocks in
Florida.
Stakeholder Workshop Evaluation
Results of anonymous evaluation were positive (Table 3-4), with all participants
providing the highest possible rating for panel composition and solicitation of input along
with categories addressing communication, participation, and interaction of the panel
and project team members. High scores were given for communication of objectives
and ability to capture panel feedback, with the panel found useful by all respondents.
The overall meeting was rated good to excellent with all respondents stating they would
attend a meeting of this type in the future.
Optional comments on ways to improve the meeting were included at the end of
the survey, with three participants electing to provide feedback. Two participants
commented that adding more time would be beneficial and allow for more discussion.
There were multiple comments that the panel was very informative and organized well,
95
with a good variety of stakeholder interests and backgrounds represented. One
participant commented that, while the facilitator did a good job, having a completely
impartial facilitator may be beneficial for separating facilitation and discussion, as well
as would reduce the potential of conflicts of interest.
96
Table 3-1. FISK scores for three assessors of Alligator Gar aquaculture in Florida (mean = 4; Δ = 2). The score is the overall score of each assessor, with the overall scores the sum of the scores in each section (Biogeography/Historical (1.01 to 3.05) and Biology and Ecology (3.01 to 8.05)). Scores <1 indicate low risk, scores ≥ 1 and ≤10.25 indicate medium risk (Lawson et al. 2015).
Variable Assessor 1 Assessor 2 Assessor 3
Score 5 4 3
Risk Category Medium Medium Medium
Biogeography/Historical -1 3 0
1. Domestication/Cultivation 0 2 1
2. Climate and Distribution 1 1 1
3. Invasive Elsewhere -2 0 -2
Biology and Ecology 6 1 3
4. Undesirable Traits 3 2 3
5. Feeding Guild 2 0 0
6. Reproduction -2 1 -1
7. Dispersal Mechanisms 0 0 0
8. Tolerance and Attributes 3 -2 1
97
Figure 3-16. Distributions of certainty percentage for the answers to 49 questions of the
FISK risk screening by three assessors (Assessor 1 [blue bars], Assessor 2 [orange bars], and Assessor 3 [gray bars]) for Alligator Gar aquaculture in Florida. X-axis abbreviations are as follows: VU = very uncertain, MU = mostly uncertain, MC = mostly certain, and VC = very certain.
98
Table 3-2. FISK version 2 assessment for Alligator Gar for Florida. The Q ID column corresponds to question identification codes in FISK. Answer codes are N = no, Y = yes, and ? = don’t know and are separated to show answers, justification, and certainty of the two independent assessors. Certainty codes are 1 = very uncertain, 2 = moderately uncertain, 3 = moderately certain, and 4 = very certain.
Q ID
Question Answer Justification Certainty
1.01 Is the species highly domesticated or widely cultivated for commercial, angling or ornamental purposes?
N Cultured by agencies for stock enhancement in a few states and some culture as an ornamental in SE Asia but not widely cultivated.
3
Y There is no indication that the taxon has been grown deliberately for at least 20 generations, however, Alligator Gar are known to be easily reared in captivity to provide broodstock for angling and restoration in several federal hatcheries in the US. Broodstock are easily maintained and spawn readily in captivity (Mendoza et al. 2002).
3
Y It is not clear whether this species is highly-domesticated and reared for 20 generations, which would extend back at least 60 years. However, Chong et al. (2010; Journal of Fish Biology) indicate that Alligator Gar are cultivated in Malaysia. Patterson et al. (2018; North American Journal of Aquaculture) report on Alligator Gar volitionally spawning in small aquaculture ponds designed for small ornamental fish.
3
1.02 Has the species established self-sustaining populations where introduced?
N No evidence of establishment outside native range (USGS NAS; FishBase)
3
N While the species has been identified in several countries outside of its native range, there is no indication that the species is establishing self sustaining populations where introduced. The propagule pressure is likely low where introduced (Scarnecchia 1992), but the status of some of the introduced populations is "uncertain" leading to lack of certainty
3
? There are numerous records for Alligator Gar, including Texas in the USA and globally in Malaysia, Thailand, Iraq, and Indonesia. Fishbase indicates introductions to Hong Kong and Malaysia, but also indicate that it is not known whether they are established (https://www.fishbase.se/Introductions/IntroductionsList).
3
1.03 Does the species have invasive races/varieties/subspecies?
N No evidence of this and no established populations. 3
N There is no indication in literature of the species having invasive races/varieties
3
N No evidence for invasive races, as likely none have been produced.
4
99
Table 3-2. Continued
2.01 Is the species reproductive tolerance suited to climates in the risk assessment (1-low, 2-medium, 3-high)?
3 High climate match from CLIMATCH software for Florida (see report).
4
3 The CLIMATCH software resulted in climate 6 score of 0.92 (scores over 0.103 are high) for Florida (see report)
4
3 The Climate 6 score for the potential non-native range in Florida was calculated to be 0.92, a high climate match using Climatch.
4
2.02 What is the quality of the climate match data (1-low, 2-medium, 3-high)?
3 CLIMATCH climate matching program 4
3 The native range of Alligator Gar (southeastern US) is well researched and supported in primary literature
4
3 Alligator Gar have a well-known distribution in the southern US.
4
2.03 Does the species demonstrate broad climate suitability?
N Koppen-Geiger publication by Peel et al. 2007 4
N Alligator Gar are confined to Cfa (Koppen-Geiger publication by Peel et al. 2007)
4
N Alligator Gar are largely confined to Cfa (warm temperate; fully humid; hot summer).
3
2.04 Is the species native to, or has established self-sustaining populations in, regions with similar climates to the RA area?
Y Alligator Gar is native to a small portion of the RA in NW Florida and naturally occurs in similar climate to a large portion of the RA. (Biological Synopsis and Peel et al. 2007)
4
Y Alligator Gar native range in the Florida panhandle corresponds to the Cfa area that encompasses most of the RA area (peninsular Florida). The southern tip of Florida is part of the RA area and not within the Cfa range of climate.
3
Y The Cfa climate region extends south in Florida approaching Naples on the west coast and Jupiter on the east coast.
4
100
Table 3-2. Continued
2.05 Does the species have a history of being introduced outside its natural range?
Y Some instances of single specimens collected outside native range (USGS NAS, FishBase) and some stocking in SE Asia as a sportfish.
4
Y Yes, there are multiple reports documented where the species has been recorded outside of its native range (Malaysia, Hong Kong, cultured in SE Asia; Biological synopsis) for sport and ornamental interests.
4
Y USGS NAS (https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=755) indicates nonindigenous occurrences in California, South Carolina, and Texas. The species has also been reported from the east coast of Florida. Chong et al. (2010; Journal of Fish Biology) also reports the Alligator Gar from Malaysia and Fishbase (Froese and Pauly 2019) list Hong Kong and Malaysia as sites of introduction.
4
3.01 Has the species established one or more selfsustaining populations beyond its native range?
N No known established populations (USGS NAS, FishBase)
3
N There is no indication of the species establishing one self sustaining population, so more is not likely. The status of the Alligator Gar found outside of their native range is extirpated, not reproducing, or unknown
3
? Noted from Malaysia, Thailand, Iraq, and Indonesia. Fishbase indicates introductions to Hong Kong and Malaysia, but also indicate that it is not known whether they are established (https://www.fishbase.se/Introductions/IntroductionsList.php?ID=1073GenusName=Atractosteus&SpeciesName=spatula&fc=34&StockCode=1089).
4
3.02 In the species’ introduced range, are there impacts to wild stocks of angling or commercial species?
N No established populations. 3
N There is evidence that, while the species is mostly piscivorous, the majority of its diet is made of rough fishes. It has been established that Alligator Gar are not voracious predators of game fish or commercial species
2
N No known impacts to wild stocks of angling or commercial species; this species has no verified non-native populations that are self-sustaining.
3
101
Table 3-2. Continued
3.03 In the species’ introduced range, are there impacts to aquacultural, aquarium, or ornamental species?
N No established populations 3
N There is little information on impacts recorded in the species introduced range as they have not been established outside of their native range
3
N No known introduced populations which are self-sustaining; thus no known impacts, where the Alligator Gar would be unlikely to interact with aquacultural or ornamental species
4
3.04 In the species’ introduced range, are there impacts to rivers, lakes or amenity values?
N No established populations. 3
N There is little information on the species in its introduced range, there is no indication that the species has an impact on rivers, lakes, or amenity values in the native range
3
N No evidence for impacts to rivers, lakes, or amenity values.
3
3.05 Does the species have invasive congeners?
N The congeners Tropical Gar A. tropicus and Cuban Gar A. tristoechus are not known to be invasive. No Lepisosteus gar known to be invasive.
3
N There is no indication of invasive congeners in literature 4
N There are two related species, Cuban Gar Atractosteus tristoechus and Tropical Gar Atractosteus tropicus, both of which do not have known introductions according to Fishbase (Froese and Pauly 2019).
4
4.01 Is the species poisonous/venomous, or poses other risks to human health?
N Not poisonous/venomous. No known threat to human health. Gar eggs are toxic if eaten (Fuhrman et al. 1969). Fuhrman, F.A., Fuhrman, G.J., Dull, D.L. and Mosher, H.S., 1969. Toxins from eggs of fishes and Amphibia. Journal of Agricultural and Food Chemistry, 17:417-424.
3
N The species is not poisonous or venomous to human health, the large size is intimidating but there is no record of the species being harmful to human health. There are indications that the species is more inclined to avoid human contact. The eggs of the Alligator Gar are toxic to mammals (Boschung and Mayden 2004)
3
N While the Tropical Gar is considered poisonous to eat (Froese and Pauly 2019), the Alligator Gar is not considered venomous, poisonous, or a risk to human health, River Monsters, notwithstanding (http://www.animalplanet.com/tv-shows/river-monsters/fish-guide/alligator-gar-texas-usa/).
4
102
Table 3-2. Continued
4.02 Does the species out-compete with native species?
N No established populations and thus no evidence of this. 1
N There is no indication in literature of this, there is evidence that Alligator Gar feed mostly on rough fishes and little on game species. Felterman (2015) found that Alligator Gar were beneficial to sportfish populations which could be indicitive of the relationship with native species. Texas Parks and Wildlife Department state that water with healthy Alligator Gar populations have healthy sportfish populations. Scarnecchia (1992) views Alligator Gar as a natural species in the ecosystem community
3
N No evidence for competition with native species. 3
4.03 Is the species parasitic of other species?
N Not a parasite. 4
N There is no indication that the species is parasitic of other species in literature
4
N No evidence for the Alligator Gar being parasitic of other species.
4
4.04 Is the species unpalatable to, or lacking, natural predators?
N Humans fish for Alligator Gar, resulting in many declining and imperiled populations (Scarnecchia 1992; Buckmeier 2008). Small juveniles likely vulnerable to a wide range of predators.
4
N Alligator Gar have few natural predators, especially beyond the larval stage as they grow quickly. Their meat is safe for consumption but the eggs are toxic to mammals, reptiles, and crustaceans (Boschung and Mayden 2004; biological synopsis) and the only noted natural predators are humans and alligators (Ross 2001)
2
N Human harvesting can lead to an unsustainable population if harvest exceeds 6.5% (Smith et al. 2017; Transactions of the American Fisheries Society). Further, natural predation is likely, at least up to a certain size.
4
4.05 Does the species prey on a native species previously subjected to low (or no) predation?
N Florida has other large predatory fishes (e.g., Common Snook Centropomus undecilmalis, Atlantic Tarpon Megalops atlanticus; Longnose Gar Lepisosteus osseus). Otherwise, this species is unlikely to occur in habitats in close proximity to imperiled species.
3
N Florida has large predatory fishes and there is literature on the beneficial effect of Alligator Gar on native sportfish populations or commercially important native fish (TPWD; Scarnecchia 1992; Felterman 2015)
1
N The question help suggests the species should be likely to establish in a system where fish are likely to be absent; however, Alligator Gar inhabit large systems such as bayous, swamps, rivers, etc.., locations which are unlikely to be fishless.
4
103
Table 3-2. Continued
4.06 Does the species host, and/or is it a vector, for one or more recognized nonnative infectious agents?
N No OIE-listed notifiable pathogens (OIE) 3
N There is no indication in literature, no OIE listed pathogens
3
N There are no known OIE reportable diseases of the Alligator Gar; further, with close proximity to the risk assessment area, non-native infectious agents are unlikely.
3
4.07 Does the species achieve a large ultimate body size (i.e., >15 cm total length) (more likely to be abandoned)?
Y Maximum length about 3 m and commonly up to 2 m (FishBase)
4
Y The species does achieve a large ultimate body size (3m), as ornamental species the large size may make it more likely to be abandoned.
3
Y Fishbase (Froese and Pauly 2019) indicate a maximum length of 305 cm.
4
4.08 Does the species have a wide salinity tolerance or is euryhaline at some stage of its life cycle?
Y Adults survive in 35 ppt sea water (Suchy 2009; Green et al. 2015). Juveniles and larvae are less tolerant of elevated salinity (Schwartz and Allen 2013; Green et al. 2015).
4
Y The species has a salinity tolerance of 35 ppt (biological synopsis) but no euryhaline life cycle stage
4
Y Juveniles can tolerate salinity at 24 ppt for 30 days (Schwarz and Allen 2013; Comparative Biochemistry and Physiology), but larvae exhibit lower tolerance (8 ppt). Adults can tolerate salinity at 35 ppt (Buckmeier 2008; https://tpwd.texas.gov/publications/nonpwdpubs/media/gar_status_073108.pdf).
4
4.09 Is the species able to withstand being out of water for extended periods (e.g., minimum of one or more hours)?
Y Air-breather (Omar-Ali et al. 2016). Omar-Ali, A., Baumgartner, W., Allen, P.J. and Petrie-Hanson, L., 2016. Fine Structure of the Gas Bladder of Alligator Gar, Atractosteus spatula. Int. J. Sci. Res. Environ. Sci. Toxicol. 1:1-8.
4
Y There is no literature on the ability of the species to withstand being out of water for extended periods, however, anecdotal evidence and tagging processes (Wegener 2017;2018) indicate some ability to withstand being out of water for periods of time
2
N No evidence for Alligator Gar exhibiting desiccation tolerance.
3
104
Table 3-2. Continued
4.10 Is the species tolerant of a range of water velocity conditions (e.g., versatile in habitat use)
N Mostly occurs in sluggish rivers and streams and their backwaters (Biological Synopsis).
3
N Alligator Gar exhibit preferences for slow moving rivers and oxbows, however, they have found that there are distinct populations that also exhibit preferences for estuarine bays compared to rivers and oxbows
3
N Alligator Gar exhibit a preference for lower to moderate flowing water (Kluender 2016; Ecology of Freshwater Fish).
2
4.11 Does feeding or other behaviours of the species reduce habitat quality for native species?
N No evidence of this was found. 3
N There is nothing in the literature to indicate that the feeding or behavior of Alligator Gar reduces the habitat quality for native species. Alligator Gar feed on rough fishes, but there is no local extirpation of rough fishes noted in native areas and they are considered beneficial for sportfish populations (biological synopsis). They do not forage or burrow
3
N No evidence for eco-engineering activities which would reduce the habitat quality for native species.
4
4.12 Does the species require minimum population size to maintain a viable population?
? No evidence for this was found. 2
? There is nothing in literature to specifically indicate a minimum population size to maintain viable populations
3
Y Smith et al. (2017: Transactions of the American Fisheries Society) report that a modest harvest of 6.5% a year would result in overharvesting, which is quite different than some commercially-harvested species. This would seem to suggest that a minimum population size would be required. Smith et al. (2017; Transactions of the American Fisheries Society) suggest: "Alligator Gar populations were highly sensitive to exploitation in our model simulations."
2
5.01 If the species is mainly herbivorous or piscivorous/carnivorous (e.g., amphibia), then is its foraging likely to have an adverse impact in the RA area?
Y Very large, predatory species (>2 m in total length). May increase predation pressure on native fish, crustaceans, and amphibians/reptiles.
1
N The species is mainly piscivorous, however, it has been indicated that it is beneficial to sportfish despite its feeding habits (biological synopsis)
2
? Alligator Gar do not have reported impacts in their native range, which could be due to the lack of research or that they occur at relatively low density. However, Alligator Gar were also deliberately culled, leading to extirpation in some regions. There is some suggestion that this could be due to their impact on sportfish populations.
3
105
Table 3-2. Continued
5.02 If the species is an omnivore (or generalist predator), then is its foraging likely to have an adverse impact in the RA area?
N Not an omnivore. 3
N The species is mainly piscivorous, but also considered an opportunistic feeder noted to have blue crabs and human waste products found in their stomachs (biological synopsis). There is no indication in literature that Alligator Gar are adversely impacting the surrounding area
2
N While Alligator Gar will undergo ontogenetic dietary changes, however this species is not an omnivore
2
5.03 If the species is mainly planktivorous, detritivorous or algivorous, then is its foraging likely to have an adverse impact in the RA area?
N Not in these trophic groups. 4
N The species is not planktivorous, detritivorous, or algivorous
4
N Not considered mainly planktivorous, detritivorous, or algivorous.
4
5.04 If the species is mainly benthivorous, is its foraging likely to have an adverse impact in the RA area?
N Mainly a piscivore, but does consume some crustaceans.
3
N The species is mostly piscivorous and an ambush predator, waiting for fish to swim right by its head to feed (biological synopsis)
4
N Not considered mainly benthivorous, but will consume benthic organisms such as Blue Crabs.
4
6.01 Does the species exhibit parental care and/or is it known to reduce age-at-maturity in response to environment?
N No parental care (Boschung and Mayden 2004). 4
N In the wild and captivity, once eggs are fertilized there is no further parental care (biological synopsis)
4
N Alligator Gar do not exhibit parental care. 4
6.02 Does the species produce viable gametes?
Y Numerous references. 4
Y When spawning conditions are met, Alligator Gar produce viable gametes in captivity and the wild. There are no functionally sterile Alligator Gar noted in literature
4
Y Not a sterile hybrid. 4
106
Table 3-2. Continued
6.03 Is the species likely to hybridize with native species (or use males of native species to activate eggs) in the RA area?
N Evidence of confirmed hybridization occurred in captivity between Alligator Gar and Longnose Gar. Herrington, S.J., Hettiger, K.N., Heist, E.J. and Keeney, D.B., 2008. Hybridization between longnose and alligator gars in captivity, with comments on possible gar hybridization in nature. Transactions of the American Fisheries Society 137:158-164.) A small percentage of Alligator Gar and Longnose Gar in Texas were hybrids (Bohn et al. 2017). The authors noted that these species spawn in different habitats, making hybridization less likely. Hybridization, though possible, would most likely be rare.
2
Y There is evidence of hybridization in the wild and captivity of Alligator Gar with Longnose Gar (biological synopsis). There is ongoing research to examine if hybridization has occurred in Florida
2
Y Herrington et al. (2008; Transactions of the American Fisheries Society) indicate: "This conclusive evidence of intergeneric hybridization in the gars may provide insights into phylogenetic relationships in Lepisosteidae and hybridization theory and may explain unsubstantiated reports of gar hybridization in nature and the pet trade." However, without data from the wild, it is not known how likely this will be, especially for Longnose Gar in regions where Alligator Gar are not native, which might lead to a lack of reproductive isolation.
3
6.04 Is the species hermaphroditic?
N No evidence found. 3
N There is no evidence in literature of hermaphordites 3
N No evidence that the Alligator Gar exhibits routine or even occasional hermaphroditism.
3
6.05 Is the species dependent on the presence of another species (or specific habitat features) to complete its life cycle?
N Alligator Gar spawns often in flooded backwaters in association with aquatic vegetation, submersed terrestrial vegetation, or woody debris (Metee et al. 1996).
3
Y No dependence on another species. Alligator Gar are dependent on freshwater for successful spawning, mostly on floodplains during flooding periods and over submerged vegetation for the eggs to adhere to (biological synopsis)
3
? No evidence for dependence on other species. 3
107
Table 3-2. Continued
6.06 Is the species highly fecund (>10,000 eggs/kg), iteropatric or has an extended spawning season relative to native species?
N Average fecundity is about 4 eggs/g female body weight (= 4,000 eggs/kg). Metee et al. 1996.
4
N Alligator Gar fecundity increases with size, periodic life history strategists. They spawn when conditions for spawning are met (biological synopsis) and produce up to 4.1 eggs/g (4100eggs/kg) (Ferrera 2001; biological synopsis)
2
? Fecundity is thought to be highly variable (https://tpwd.texas.gov/publications/nonpwdpubs/media/gar_status_073108.pdf), but could be around 4.1 eggs per gram of body weight (Ferrera 2001; Dissertation; Auburn University). Ultimately, this is thought to be a mean estimate and higher estimates could be reasonable.
3
6.07 What is the species’ known minimum generation time (in years)?
4 Patterson et al. 2018. 4
4 4-10, minimum recorded age of sexual maturity and spawning is 4 (biological synopsis, Patterson et al.) however, average accepted sexual maturity is 6 (males) and 11 (females) (biological synopsis; Boschung and Mayden 2004)
3
>10 FishBase (Froese and Pauly 2019) indicate low resilience, late sexual maturation, and average fecundity, to contribute to a high population doubling time. There are few ways to actually determine whether this is actually the case; thus, selected "mostly uncertain".
2
7.01 Are life stages likely to be dispersed unintentionally?
N Little chance of unintentional dispersal. 3
N Human movement not likely as eggs are submerged and adhesive to plant material, young/larval stage do resemble sticks but are recognizable for movement and not likely to be overlooked
3
N No evidence for unintentional dispersal. 3
108
Table 3-2. Continued
7.02 Are life stages likely to be dispersed intentionally by humans (and suitable habitats abundant nearby)?
Y Humans frequently move fish of food or sportfish importance.
4
Y There are places (SE Asia, Texas) that value Alligator Gar for fishing potential. There were dispersals intentionally by humans in Hong Kong, releasing Alligator Gar that were bought for (presumably; USGS) ornamental purposes in a retention pond in a park (biological synopsis)
2
Y According to USGS NAS (quoted as a personal communication with Pam Fuller: ttps://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=755), Alligator Gar are popular in the aquarium trade, exhibit large maximum body size (potential tank buster), which would be most likely to be released. However, the question remains, are there suitable habitats outside of the panhandle region of the state. This is not entirely clear; thus, selected mostly uncertain.
2
7.03 Are life stages likely to be dispersed as a contaminant of commodities?
N Unlikely to be a contaminant of other commodities. 3
N In RA area, there will be no live Alligator Gar sold for meat, and only live sale will be for out of state ornamental sale
3
N No evidence for dispersal as a contaminant; while considered popular in the aquarium trade (https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=755), unlikely to accompany other shipments.
4
7.04 Does natural dispersal occur as a function of egg dispersal?
N Alligator Gar eggs are adhesive and stick to vegetation or sediments.
4
N Eggs are adhesive and attach to substrate once laid and fertilized in low flow flooded area until hatching (biological synopsis)
4
N Eggs are adhesive, limiting egg dispersal (Mettee et al. 1996; Fishes of Alabama and the Mobile Basin).
4
7.05 Does natural dispersal occur as a function of dispersal of larvae (along linear and [or] ‘stepping stone’ habitats)?
? No information found. 2
N There is no direct literature regarding currents and Alligator Gar larvae, however, eggs and larvae are laid in low flow, shallow, flooded areas (biological synopsis). The likelihood of natural dispersal is low
2
? Thought to sink if not actively swimming (Mettee 1996; Fishes of Alabama and the Mobile Basin).
3
109
Table 3-2. Continued
7.06 Are juveniles or adults of the species known to migrate (spawning, smolting, feeding)?
Y Alligator Gar move more during warmer months and some individuals may travel long distances (Wegener et al. 2017)
3
Y Adult Alligator Gar move large distances, potentially due to resource partitioning (Weneger 2017;2018; Biological Synopsis). In Florida, there is seasonal variation in movement, with most happening in the warmer months. The linear home range for Alligator Gar in Florida was 41.32 km, in Alabama the greatest recorded movement for Alligator Gar is 10.2 km (Boschung and Mayden 2004; biological synopsis)
4
Y Highly mobile species depending upon habitat: 1) 0.89 to 101.58 km in Pensacola Bay (Wegener et al. 2017); 2) home ranges to 60 km, with some to 100 km (Buckmeier et al. 2013); 3) home range from 6.57 to 16.7 km (Sakaris et al. 2003; Brinkman 2003).
4
7.07 Are eggs of the species known to be dispersed by other animals (externally)?
N No evidence found 2
N There is no evidence of this in literature 3
N No evidence for dispersal by other animals externally. 4
7.08 Is dispersal of the species density dependent?
? No information found. 1
? There is nothing in literature to indicate that dispersal is species density dependent. During the winter and spawning Alligator Gar form larger aggregations, in the warmer months they are farther dispersed (Wegener 2017; 2018; biological synopsis)
1
? No evidence for density dependent dispersal, which could be due to difficulty in assessing the population status of Alligator Gar, or that they naturally occur at lower density than most fish species.
3
8.01 Are any life stages likely to survive out of water transport?
Y Larger juveniles and adults can survive periods out of water (air breather).
4
Y No literature that specifically references ability to survive outside of water, adults have been noted to survive periods of time out of water (air breathers)
3
? No specific evidence for ability to survive out of water transport. However, there are anecdotal accounts of extended periods out of the water.
3
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Table 3-2. Continued
8.02 Does the species tolerate a wide range of water quality conditions, especially oxygen depletion and temperature extremes?
Y Air-breathing allows Alligator Gar to use hypoxic waters (Schultz 2004; Omar-Ali et al. 2016). The species also tolerates a wide temperature range (Biological Synopsis).
4
Y Alligator Gar are found in a range of water quality conditions and are noted to survive low DO (air breathers), temperatures from 1-30C (biological synopsis)
4
Y The native distribution of Alligator Gar extends to Illinois, with temperatures below 5C; at the southern portions of the range temperature can exceed 30C. Can tolerate a range of DO because of a modified swim bladder.
3
8.03 Is the species readily susceptible to piscicides at the doses legally permitted for use in the risk assessment area?
Y Gar are frequently collected using rotenone, often at lower doses than allowed by the label (e.g., 3 vs 5 ppm). However, gar are more resistant than many fishes (Hubbs 1963). Hubbs, C., 1963. An evaluation of the use of rotenone as a means of" improving" sports fishing in the Concho River, Texas. Copeia, 1963(1), pp.199-203. Some gar may survive rotenone treatments.
2
Y Little literature on the topic; gar are collected with rotenone at levels lower than recommeneded on label. Gars are more resistant than other species as they are air breathers (Hubbs 1963). EDIS recommends 2 ppm and 5% rotenone applied at 1.5 ppm did not effect Alligator Gar (Harris et al. 1973) but did affect other gar species.
2
Y Higginbotham and Steinbach (Renovation of Farm Ponds; TAMU extension) indicate gar (not specific to Alligator Gar) can be difficult to kill with rotenone. Hoyer and Canfield (1994; Handbook of Common Freshwater Fish in Florida Lakes) routinely sampled gar with rotenone and blocknets. Thus, Alligator Gar may exhibit at least a baseline susceptibility to rotenone. Lower certainty was selected.
3
8.04 Does the species tolerate or benefit from environmental disturbance?
Y Flooding benefits reproduction and potentially recruitment of Alligator Gar through increased access to spawning habitat and juvenile/nursery habitat.
3
N Environmental disturbances are not tolerated by Alligator Gar, the specific needs for spawning are impaired by environmental disturbance and reduce successful spawning (e.g. building of dams restricting floodplains)
3
N No evidence that the Alligator Gar benefits from disturbance; in fact, it may be just the opposite. Dam construction has altered habitat availability, which is thought to have contributed to a decline of the Alligator Gar in part of its range (Mettee et al. 1996. Fishes of Alabama and the Mobile Basin).
3
111
Table 3-2. Continued
8.05 Are there effective natural enemies of the species present in the risk assessment area?
N Although some predators would consume larval and juvenile Alligator Gar, adults would be resistant to most predators except for Alligators, Otters, and Humans.
3
N Alligator Gar have few natural enemies, but the RA area has both alligators and humans in close vicinity. Alligator Gar outgrow alligator quickly and the human impact is low
3
Y At least for larval, juvenile, and subadult Alligator Gar, effective predators would be other gar species, catfish, bass. However, when they reach a certain size, only alligators and humans would be effective predators.
3
Figure 3-17. Distributions of FISK risk category scores with the average and standard deviation.
112
Table 3-3. Breakout groups and overall risk assessment results. Opinions different within groups where there are multiple risk ratings or certainty values. The composition of breakout groups differed for the two sections (establishment and consequences). Risk levels are H = High, M = Medium, and L = Low. The overall risk of establishment is the lower of the four ratings and the overall risk of consequences is the highest rating between environmental and economic (unless both are low, then social/political). The ORP is the average of establishment and consequences, rounded up. Certainty levels are as follows: VU = very uncertain, RU = reasonably uncertain, MC = moderately certain, RC = reasonably certain, and VC = very certain.
Risk Type Category Group 1 Group 2 Overall Group
Risk Level
Certainty Risk Level
Certainty Risk Level
Certainty
Probability of Establishment
Presence in Pathway
H
RC
H H
VU VC
H H
RC VC
Introduction H
MC
H H
RC MC
H H
MC RC
Colonization M L-M
VU VU
M L-M
L
RU RU RU
L-M M
VU RU
Spread L L H
RU MU RC
M MC L M H
MC MC MC
Overall M L-M L-M
Consequences of Establishment
Environmental M VU L L M
RC MC RU
L-M M
RU RU
Economic M M
RU MC
L L M
RC MC MC
M L
MC MC
Social/political L VU L-M M
RC MC
L-M RU
Overall M M M
Overall Risk Potential (ORP)
M M M
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Table 3-4. Results of the evaluation of the stakeholder risk assessment workshop. All participation was anonymous, with seven attendees providing answers following the completion of the workshop. Please rate how well this meeting did each of the following:
(Not at all) 1 2 3
(Very Well) 4
Informed about the objective of the meeting/panel
29% 71%
Informed about risk assessment and management
43% 57%
Gathered participants of varying expertise for the stakeholder panel
100%
Gathered input from participants 100%
Accurately captured the output (Generic Analysis and risk management) of the panel
14% 86%
Please state your level of agreement with the following statements:
Strongly Disagree
Disagree Agree Strongly Agree
I was able to communicate my ideas 100%
Others heard my ideas 100%
I heard the ideas of others 100%
To what extent did you find the stakeholder panel useful? (Not at
all) 1 2 3 4 5 (Very)
- - - 57% 43% How would you rate the meeting overall?
(Poor) 1 2 3 4 5 (Excellent)
- - - 43% 57% Would you attend future meetings of this type?
No Maybe Yes
- - 100%
114
CHAPTER 4 DISCUSSION
Increasingly, natural resource managers are concerned with the impacts of
introductions of non-native species on native species and ecosystems (Elvira and
Almodóvar 2001; Gozlan et al. 2010; Cucherousset and Olden 2011). Overall Alligator
Gar risk to Florida, in the native and non-native range, was determined to be medium.
The risk screen estimated a low-medium risk level for Alligator Gar, an outcome largely
in agreement with the comprehensive assessment completed by a stakeholder panel.
Factors increasing the invasion potential of Alligator Gar were salinity tolerance, high
migration potential, and data gaps in Alligator Gar biology. Factors that decreased the
risk potential of Alligator Gar aquaculture in Florida were the lack of invasion history and
lack of documented impacts in and outside of the native range. Ultimately, the risk
assessment concluded that if cultured responsibly, this native fish in aquaculture
presents a low-medium invasion potential.
The FISK and Generic Analysis results were similar to a U.S. federal risk screen
of Alligator Gar (USFWS 2017). The U.S. Fish and Wildlife Service completed an
Ecological Risk Screening Summary (ERSS) screening of Alligator Gar for the entire
United States and found that the perceived risk of Alligator Gar outside of their native
range is uncertain, their equivalent to medium risk, indicating additional assessment
was needed (U.S.F.W.S. 2017). The FISK results did not necessarily mean that
additional assessment was required, conservative risk tolerance led to the additional
assessment of a Generic Analysis. On further assessment, the medium risk rating was
confirmed.
115
The risk assessment of Alligator Gar suggested lower risk than that determined
by previous risk assessments of large-bodied, predatory fishes in Florida. Arapaima risk
for the state was medium overall, with a minimal high score in subtropical and tropical
south Florida (Hill and Lawson 2015). Management agencies determined that current
conditional species regulations provided adequate risk mitigation to allow culture (Hill
and Lawson 2015). The Barramundi Perch assessment resulted in a high risk rating, yet
the agencies concluded that increased more stringent conditional provisions were
acceptable risk mitigation to allow commercial culture (Hardin and Hill 2012). The main
change mandated indoor, tank culture only.
Additionally, many ornamental species that are currently in the aquarium trade in
Florida have higher FISK risk scores than Alligator Gar. The Neon Tetra Paracheirodon
innesi, Guppy Poecilia reticulata, and Betta Betta splendens all have FISK scores of 5
for Florida (Lawson et al. 2015; Figure 4-1). These small ornamental species have
comparable low-medium risk scores to Alligator Gar.
High numbers of historic introductions of freshwater fishes, both successful and
failed, provide insights into the types of fishes most likely to prove invasive. Life history
traits characteristic of species with success potential in Florida include parental care, air
breathing, no fluvial dependence, moderate or large body size, and large eggs (Lawson
2018). Successful species trend towards the equilibrium strategy within the Winemiller
and Rose (1992) triangular life history model (Lawson 2018). Non-native species with
no parental care have a history of failing to establish in Florida, with one exception
(Oriental Weather Loach Misgurnus anguillicaudatus; Lawson 2018). Alligator Gar is a
periodic life history strategist (Winemiller and Rose 1992) with late sexual maturity and
116
a partially fluvial-dependent reproductive strategy, both traits are not associated with
success in establishing outside of their native range in Florida (Lawson 2018).
Florida has seemingly suitable habitat in the coastal river systems along the
northern Gulf of Mexico coast, including the Suwannee River in Florida’s Big Bend.
While the Alligator Gar have an extended spawning period across its native range
(January to September; Echelle and Riggs 1972), flood periods in the peninsula may
not coincide with spawning habits.
Specific questions related to potential establishment in Florida include the lack of
observed population increases within the native Florida range despite more than a
decade of harvest closure and protection as well as failure to move beyond the western
panhandle. There is no explanation in literature for why Alligator Gar have not moved
into peninsular Florida. The lack of movement suggests a strong barrier to spread and
establishment is present, that the low-density populations of Alligator Gar in Florida may
represent a peripheral population that exists at the edge of their native range, and it has
been proposed that eastern populations of Alligator Gar are more marginal and have
less reproductive output.
The Longnose Gar Lepisosteus osseus displays similar distribution to Alligator
Gar in the southeast United States; found in Gulf Slope drainages from central Florida
to Rio Grande drainage in Texas and Mexico as well as the panhandle (Froese and
Pauly 2019). Dispersal does not appear to be the barrier, as long-range movement
(linear home ranges up to 101 km in Florida; Wegener et al. 2017) has been recorded
across the native range, the wide salinity tolerance of adults, and the propensity to use
bays, estuaries, and marine habitats for habitat and dispersal. The species native range
117
extends further south latudinally through Mexico, to the Rio Papaloapan Basin in
Veracruz, Mexico (Figure 4-2; Miller 2005). The CLIMATCH map (Figure 3-11) indicates
that a large proportion of the number of match cells at this data point in Veracruz,
Mexico contributed to the target region match score and contribution to the CLIMATCH
locations. Seasonal variation in ovarian weight indicated peak spawning in July and
August in northeastern Mexico (Garcia de Leon et al. 2001) while April to June is
generally accepted as the spawning season for Alligator Gar throughout their native
range (Suttkus 1963; Garcia de Leon et al. 2001; Miller 2005). Oklahoma, Texas, and
Alabama report a broader spawning period, January to September. Spawning
throughout the native range of Alligator Gar is reported with flooding (Suttkus 1963;
Garcia de Leon et al. 2001; Miller 2005), with the highest rainfall in Mexico reported in
June to September, consistent with the peak spawning period indicated by Garcia de
Leon et al. (2001; https://weather-and-climate.com/veracruz-July-averages). Peninsular
Florida and the native range of Alligator Gar in Mexico are very similar in latitude,
rainfall, and temperature (CLIMATCH). A high climate match does not mean the habitat
is suitable for an organism, as evidenced by the potential barriers preventing successful
spawning and recruitment.
General comments on the benefits of Alligator Gar aquaculture are positive if risk
mitigation (FDACS) is updated to reflect and manage the potential genetic implications
(e.g. Longnose Gar and Florida Gar) in the peninsula. Risk of escape was considered
low at the production level due to risk mitigation factors, including BMPs and potential
increased regulations for production, permitting, and transfer. There are further scientific
benefits of understanding Alligator Gar biology and reproduction, as well as potential for
118
Alligator Gar stock enhancement in Florida. Allowing commercial culture of Alligator Gar
also presents a chance to reduce illegal trade and introductions of unknown diseases as
a result of import for sale.
Data Gaps and Research Recommendations
Several data gaps, identified throughout the risk assessment process, exist for
Alligator Gar. Some of the listed data gaps are currently under research by FWC. Data
gaps provide guidelines for research recommendations and identification of potential
hazards to inform management decisions. Additional research and assessment would
decrease uncertainty of risk perception and inform the risk potential for Florida.
Research recommendations (some are currently undertaken or planned with
FWC) that would fill or partially fill data gaps include: effects of hybridization of Alligator
Gar with other species, population dynamics and spread potential, investigation of
“brackish water” populations, reproduction requirements, potential genetic impacts on
native Alligator Gar from commercial aquaculture, potential to use commercial
aquaculture as a source for Alligator Gar stock enhancement, predator-prey dynamics,
and population dynamics and spread modeling studies. Recent and ongoing studies by
agencies throughout the native range of Alligator Gar would provide data sources and
procedures to support similar evaluations and projects in Florida.
Management Implications and Risk Mitigation
Allowing commercial culture of Alligator Gar in Florida would be consistent with
the outcome of the risk assessment effort. Also, culture of Alligator Gar would already
be legal if not for the fishing and possession ban imposed on Alligator Gar in Florida
due to uncertainty concerning abundance and dynamics in Florida.
119
The predicted risk assessment was based on no live sales in Florida, other than
to those who hold necessary permits. If live sales are considered, the question of if
there would be an increase in risk would need to be further assessed. Discussion on
this topic determined that as it is present already, it would likely be a marginal increase.
Aquaculture of a medium risk species in Florida is common and consistent with
aquaculture BMPs in general (FDACS 2019), and for some medium risk species with
specific concerns, the conditional species provisions. A number of species that are
classified high risk are cultured under conditional species provisions (e.g. Barramundi
Perch, Hardin and Hill 2012; Arapaima, Hill and Lawson 2015). Conditional species
provisions include strict containment, sales, and record keeping practices, and, in some
cases, indoor culture. If restricted species are permitted to be cultured outdoors, the
lowest point of the top edge of the pond berm must be one foot above the 100-year
flood elevation issued by FEMA (FDACS 2019).
Florida aquaculture BMPs provide risk mitigation concerning escape from
aquaculture facilities of all cultured species (Tuckett et al. 2016; 2016b). Mitigation
efforts would need to be primarily focused on biosecurity, record keeping, and limits as
to who can possess Alligator Gar in Florida. If additional risk mitigation was deemed
necessary, extra conditions would be placed on Alligator Gar aquaculture. Conditional
species level containment would include no live sales in the state to anyone without the
appropriate permits; this would preclude sales of live food fish, ornamentals, or pond
stockers. Additional site restrictions can also be imposed to prevent culture in the
watershed of the native range of Alligator Gar. Should additional research and
assessment be completed, the recommendations would be adjusted accordingly.
120
Understanding the risk potential of Alligator Gar in Florida is important to support
management decisions, for management or policy recommendations and risk mitigation
methods. The risk assessment process identifies the level of acceptable risk and
concerns of stakeholders, which are used to determine risk mitigation methods and
support future management decisions based on a spectrum of risk tolerance.
121
Figure 4-1. FISK scores of five ornamental or food fish species compared to Alligator Gar. The orange line represents the calibrated 10.25 invasive/non-invasive threshold for Florida.
Figure 4-2. Distribution of Alligator Gar in Mexico (Miller 2005).
122
APPENDIX A STAKEHOLDER GENERIC ANALYSIS WORKSHEET
Group Number_____
Probability of Establishment Rating: L = Low, M = Medium, H = High Certainty: VU = Very Uncertain; RU = Reasonably Uncertain; MC = Moderately Uncertain; RC = Reasonably Certain; VC = Very Certain
1. Nonindigenous Aquatic Organisms Associated with Pathway (at Origin) - Estimate the probability of the organism being on, with, or in the pathway (e.g. does the organism show a convincing temporal and spatial association with the pathway?).
2. Entry Potential - Estimate the probability of the organism surviving in transit (characteristics of this element include hitchhiking ability in commerce or whether it is deliberately introduced (e.g. biocontrol agent or fish stocking)).
Rating: L M H Certainty: VU RU MC RC VC
Rating: L M H Certainty: VU RU MC RC VC
Justification: Justification:
123
3. Colonization Potential - Estimate the probability colonizing and maintaining a population (characteristics include the organism coming in contact with adequate food resource, encountering appreciable abiotic and biotic environmental resistance, and the ability to reproduce in the new environment).
4. Spread Potential - Estimate the probability of the organism spreading beyond the colonized areas (characteristics of this element include ability for natural dispersal, ability to use human activity for dispersal, and the estimated range of probable spread).
Rating: L M H Certainty: VU RU MC RC VC
Rating: L M H Certainty: VU RU MC RC VC
Justification: Justification:
124
Group Number_____
Consequences/Impacts of Establishment Rating: L = Low, M = Medium, H = High Certainty: VU = Very Uncertain; RU = Reasonably Uncertain; MC = Moderately Uncertain; RC = Reasonably Certain; VC = Very Certain
1. Economic Impact Potential - Estimate economic impact if established (e.g. economic importance of host or control costs).
2. Environmental Impact Potential - Estimate environmental impact if established (e.g. ecosystem destabilization).
Rating: L M H Certainty: VU RU MC RC VC
Rating: L M H Certainty: VU RU MC RC VC
Justification: Justification:
125
3. Perceived Impact (Social and Political Influences) - Estimate impact from social and/or political influences (e.g. aesthetic damage).
Rating: L M H Certainty: VU RU MC RC VC
Justification:
126
APPENDIX B WORKSHOP EVALUATION FORM
Please read this document carefully before participation in this study.
The purpose of these evaluations is to assess the success of the meeting.
There is no compensation for participation but know that your participation is
important. The survey is anonymous; be assured that in our analysis and
reporting of results your answers will not be connected with you. There are no
risks to you from participating in this study. Your participation in this study is
completely voluntary, you have the right not to answer any specific questions and
you may withdraw your consent at any time. There is no penalty for not
participating.
If you have any questions concerning this study, please contact: Lauren Lapham, Graduate Student Tropical Aquaculture Laboratory University of Florida Ruskin, FL 33570 Phone: (813) 671-5230 E-mail: [email protected] Whom to contact about your rights as a research participant in the study: UFIRB Office Box 11225 University of Florida, Gainesville, FL 32611-2250 Phone: (352) 392-0433 Please rate how well this meeting did each of the following:
(Not at all) 1 2 3
(Very Well) 4
Informed about the objective of the meeting/panel
Informed about risk assessment and management
Gathered participants of varying expertise for the stakeholder panel
Gathered input from participants
Accurately captured the output (Generic Analysis and risk
127
management) of the panel
Please state your level of agreement with the following statements:
Strongly Disagree
Disagree Agree Strongly Agree
I was able to communicate my ideas
Others heard my ideas
I heard the ideas of others
To what extent did you find the stakeholder panel useful?
(Not at all) 1 2 3 4 5 (Very) How would you rate the meeting overall?
(Poor) 1 2 3 4 5 (Excellent)
Would you attend future meetings of this type?
No Maybe Yes How would you improve this meeting or panel?
128
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BIOGRAPHICAL SKETCH
Lauren was born in Houston, Texas, where her family lived until moving to
Florida when she was young. Lauren has spent most of her life in Florida, growing up
swimming and riding horses. Her interest in fisheries and aquatic sciences grew with
her time on the water and outdoors.
While pursuing a Bachelor of Science in natural resource conservation at the
University of Florida, she had the opportunity to work as a science diver in Silver
Springs, assisting with collection and analysis of aquatic vegetation and increasing her
interest in the aquatic environment. In summer 2016, she had the opportunity to intern
for Sea Grant, acting as coordinator for education and outreach efforts related to
conservation and aquatic science. After graduating in 2016, Lauren began a graduate
certificate program in aquaculture and fish health with the University of Florida. She
completed her graduate certificate while working as a science diver, participating in
coral restoration, fisheries, and marine research in the Cayman Islands.
The opportunity to attend the University of Florida for a Master of Science in
fisheries and aquatic sciences arose in the Spring of 2018. Lauren began working as a
research assistant at the UF/IFAS Tropical Aquaculture Laboratory in Summer 2018,
participating in risk assessments for non-native species in Florida and assisting with
non-native species and fisheries research.
