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Module 5:Rapid response and survey techniques
Module 5:
Rapid response and survey techniquesObjectives• Participants will gain knowledge on the
survey techniques that can be used for pest fish, as well as the situations to which they are best suited
• Participants will be able to review and adjust current survey plans or develop new plans
Intended participants• Members of fish stocking groups, natural
resource management (NRM) groups, mining groups or government agencies that perform field work and may intend to carry out their own pest fish surveys
Key messages• Surveys are a vital component of pest
fish management• Several survey methods are available,
and the most suitable approach should be decided on a case-by-case basis
• The most accurate summary of the dynamics of a pest fish population requires the integration of several suitable survey methods
Learning resources• PowerPoint• Case studies• Learning activities• Publication: Australian Code of
Electrofishing Practice (Appendix F)• Field survey record sheet
Freshwater fishing restrictions Queensland:
visit <www.fisheries.qld.gov.au> and search for ‘fishing gear fresh waters’
New South Wales: visit <www.dpi.nsw.gov.au/fisheries> and search for ‘permitted methods and activities’
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Surveillance
Investigation surveys can reveal certain demographic and geographic factors that lead to a waterway being considered particularly vulnerable to a pest fish incursion (e.g. a currently uninfested catchment in close proximity to a pest fish infested area). Such identified waterways require regular surveillance in the form of pest fish surveys to ensure pest fish are not spreading. Pest fish surveillance of particular waterways can help ensure limited resources are used efficiently and increase the chances of early detection of any new infestations. It can also detect changes in overall river health and species composition over a long period of time.
Monitoring/evaluation
Once the most suitable management plan has been established for a particular incident, routine surveys are needed to evaluate management efforts. Such surveys need to be carried out not only after the implementation of management actions, but also throughout the management program. This constant influx of information allows management strategies to be adjusted if required.
Pre-intervention surveys are also important as they can be used as a reference for comparing with later surveys. If possible, it is preferable to conduct more than one pre-intervention survey to ensure that the survey wasn’t conducted during unusual conditions.
Pest fish surveys that continue long after the implementation of control actions are useful for assessing the result of specific techniques. They are therefore an important tool for recognising the most successful control methods for future pest fish incursions.
What are surveys used for?Surveys are an important tool for the management of pest fish populations, as they provide the information required to tackle the problem at hand. Pest fish surveys are conducted at many stages of a river management strategy and can be used for investigation, surveillance and monitoring/evaluation.
Figure 5.1 Field workers conducting a pest fish survey
Investigation
When a pest fish report is received for a waterbody previously considered uninfested, a preliminary survey is required to confirm the report and determine the spatial distribution of the pest fish in the waterbody. If the preliminary survey confirms the report, and finds it to be an early stage of a new incursion, spot removal may be possible before the species can become established in the catchment. The information from surveys is vital to determine the extent of the problem and the most suitable and effective management options. All pest fish investigations require consistency in their sampling effort and design to enable a comparison with other areas across the state. With this in mind, a standard procedure needs to exist for all investigation surveys.
In some cases, timely surveying and gathering of data on pest fish distribution can allow for the immediate removal or containment of the species if it is revealed to be limited to small areas and either removal or containment is considered feasible.
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Module 5:Rapid response and survey techniques
Survey methodsThere are a range of survey techniques available for gathering information on pest fish populations. Their suitability depends on:• specific features of the habitat• the species in question• the resources available• obtaining the relevant permits.
There are restrictions on the use of some fishing gear. Some of the methods involve fishing equipment that is usually not permitted to be used in freshwaters; this requires a general fisheries permit (GFP) in Queensland or a collection permit (CP) in New South Wales.
The required permits for each survey method are outlined in the following pages. Restrictions on the use of fishing gear in freshwaters can be found online. For Queensland go to <www.fisheries.qld.gov.au> and search for ‘fishing gear fresh waters’; for New South Wales, go to <www.dpi.nsw.gov.au/fisheries> and search for ‘permitted methods and activities’.
Line fishing
Line fishing is commonly used for initial investigation surveys. Specific baits are used to target different species of pest fish. Generally, earthworms and bread are used for targeting tilapia. Tilapia also respond well to the use of burley. Although line fishing in Queensland does not require a permit unless specified for a particular site or species, in New South Wales recreational line fishers are required by law to carry a receipt showing payment of the New South Wales Recreational Fishing Fee.
Permits required: None
Figure 5.2 Line fishing
Visual observation
Visual observation of pest fish can be done by scanning the waterbody from the land or a boat, or snorkeling. Snorkeling surveys are usually performed by following a series of set transects and identifying, counting and recording all fish seen along the transect. The use of video footage along transects at various depths can also be a useful survey technique. These sorts of observations are only effective when the water is clear enough.
Certain pest fish species leave behind unique traces of their presence, and the distribution and abundance of these traces can be used to deduce population parameters. An example is the nests built by male Mozambique tilapia for reproductive purposes. Information gathered can also come in the form of community reports of pest fish sightings or the observation of dead pest fish.
Permits required: None
Netting
Scoop nets or handheld dip nets can be used to capture and identify small fish accumulating near the edges of water bodies. All fish collected in the net can be emptied into a bucket full of water and sorted through; fish identified as native can be returned to the water unharmed and pest fish can be euthanised humanely.
Permits required: CP
Figure 5.3 Dip net and holding bucket
Seine nets are large fishing nets that hang vertically in the water with weights along the bottom edge and floats along the top. They are usually long and flat like a fence and may contain a pocket to help concentrate the catch for ease of removal. Seine nets are usually deployed along areas where fish are known to be accumulating. To be successful, the area to be seined should be clear of snags, large rocks and other obstructions that might catch the net and allow fish to escape.
Two people (sometimes more in heavily silted substrate) are needed to operate the net, deploying one end of the net from the water’s edge directly out towards the middle of the waterbody and then finally curving back towards the edge. Both net operators then drag their end towards themselves, each time making the area inside the net smaller. The operators must be careful not to lift the lead line of the net off the bottom, as fish will escape. The objective is to envelop the net around the fish and slowly move them toward the water’s edge so they can be manually removed and euthanised, if they are identified as a pest species.
This method may not be appropriate if native fish species such as bony bream are present within the survey area. These fish are delicate to handle, and can perish if meshed within the net.
Permits required: GFP and CP
Figure 5.4 Illustration of seine net operation
Important information!
It is sometimes very difficult to distinguish small native fish from juvenile pest fish. Therefore, before euthanising, fish should be identified by someone who has been well trained and is proficient at freshwater fish identification.
Cast nets are conical in shape with sinkers attached at regular intervals on a lead rope forming the circumference of the cone. They vary in length from approximately 4 m to 7 m. Some cast nets are designed with a lead rope tucked underneath and attached at intervals to the inner side of the net to form pockets for trapping fish.
A cast net is usually used in shallow waters and can be thrown from a riverbank, jetty or boat; it captures fish by falling and closing in on them. It takes some skill to successfully throw a cast net, as the net needs to unfold in the form of a large circle in the air and cover the largest possible area. The net then sinks to the bottom and entangles fish. As the net is brought back out of the water using a line, the sinkers come together, closing the circle around the fish as the net takes on its conical form once more.
When fishing for certain species of fish, the fisher usually sights the fish first and then throws the net, which encircles the exact spot where the fish were spotted. It is important to make sure the water is clear of any obstructions, such as snags and rocks, that might entangle and damage the cast net. Some fish species are difficult to capture with a cast net, as they quickly burrow in the substrate, avoiding capture as the sinkers close in above them. Tilapia capture via a cast net is most successful when used in conjunction with burley to aggregate the fish.
Permits required: GFP and CP
Figure 5.5 A cast net thrown into a waterbody; the structure of a cast net (right)
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Module 5:Rapid response and survey techniques
Fyke nets consist of cylindrical or cone-shaped netting bags mounted on rings with wings or leaders to guide fish towards the entrance of the bag. The end of the bag is tied closed when the net is set; when clearing the net, fish are ‘chased’ toward the end of the bag where they can be removed by undoing the tie and opening the end of the net into a large bucket of water.
A float is always placed toward the back of the net to keep an air pocket available for air breathing animals such as turtles. Metal vertical grill turtle excluders can be placed at the mouth of the fyke. This excludes most turtles from the fyke, but lets the majority of fish into the net, except for very large fish. Excluding turtles from the net protects native fish species in the cod-end of the net from predation and damage by turtles.
The nets are usually set in slow-moving or still water; nets cannot be set in fast-flowing water for logistical reasons, such as debris obstruction, damage and involuntary movement of the net downstream by currents. Burley can be used to attract fish to the net by placing a chicken pellet and corn mix (slightly wet and rolled into balls) into the bag and a trail into the wings. Stakes or weights are used to secure the wings at their desired angle as well as at the bag end to pull the net taut. Setting one wing of the net on the edge of the waterbody can prove successful as fish that feed along the edge are directed toward to trap. To take advantage of the movement of fish, the net can be set with the wings facing downstream, directing fish toward the trap as they move upstream.
The use of fyke nets has proven to be a very successful technique for catching small tilapia, especially in heavily vegetated areas where other techniques are difficult to implement. Fyke nets can be left in place for many days; however, the net must be checked and cleared daily to avoid damage to non-target animals. Setting a portion of the net above water ensures that air-breathing wildlife can be released with minimal harm.
Permits required: GFP and CP
Figure 5.6 Two fyke nets set adjacently in a waterway
Figure 5.7 A single fyke net
Figure 5.8 Bars within a fyke net act as a turtle excluder
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Trapping
A range of currently available funnel traps are useful in determining the presence of juvenile tilapia. Baits can be used in these traps to attract tilapia; this can consist of dry cat or dog biscuits, wet loaf-style cat meat, chicken pellets, bread and goldfish pellets. Traps need to be checked at least daily in order to re-bait and release bycatch.
Permits required: CP
Figure 5.9 Bait trap
Important information!When using nets and traps, keep in mind the health and safety of workers and the public. Nets and traps should only be used by suitably trained people. There are specific safety requirements that must be followed during the storage and transport of nets and traps to ensure no animals or people are injured. Equipment should not be used in areas where its operation might interfere with boat traffic and equipment must be thoroughly decontaminated to prevent the spread of aquatic weeds and animals between waterbodies. This can be done by either using chemicals such as chlorine (in low doses to prevent damage to net fabric, etc.) or by drying the gear in the sun for a few days. All visible pieces of aquatic weed should be removed.
Electrofishing
Electrofishing uses electricity to control and capture fish and can be useful for capturing larger tilapia. The electricity is generated by applying a high voltage potential between two or more electrodes that are placed in the water. The usual practice is to apply a direct current which affects the fish by causing uncontrolled muscular convulsions. This results in the fish swimming toward the anode and allows for capture (using a scoop net). Electrofishing gear comes in the form of a backpack (for shallow small streams) or can be boat mounted, where the boat itself is the cathode and the anode/s is generally mounted off the bow.
Figure 5.10 Backpack electrofishing equipment
Figure 5.11 Boat electrofishing
Due to the inherent dangers of combining water and electricity, there are important occupational health and safety issues to be considered when operating electrofishing equipment. All operators must be familiar with and comply with the Australian Code of Electrofishing Practice,
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undergo relevant training sessions and pass an electrofishing medical. Appropriate protective equipment must be worn (including rubber boots, 1000V-rated linesmen gloves and life jackets) and a qualified senior operator must be present to supervise and check equipment, clothing and operation.
Electrofishing operators must also be aware of other fauna that might be harmed. Operations must be stopped within 15 m of any animals standing in or about to drink from the waterbody, or in contact with a wire fence that enters the water. The utmost care must be taken to avoid shocking platypus, birds and other native aquatic fauna.
Permits required: GFP and CP
Figure 5.12 Backpack electrofishing
Figure 5.13 Boat electrofishing
Survey designAfter the survey methods that would best suit the site have been agreed, survey operations must follow a standard design. This allows for consistency, comparison and statistical integrity between sample sites and over time.
The following example shows the survey results for a site that was sampled using an ad hoc method in an electrofishing boat.
Pre-tilapia removal:Time arrived at site: 8.00 am
Time left site: 12 noon
Total tilapia captured: 55
Post-tilapia removal:Time arrived at site: 9.00 am
Time left site: 4.00 pm
Total tilapia captured: 107
It might appear from the survey results that the removal operation did not reduce the tilapia population size at all, as more tilapia were captured after the removal exercise than before. However, the time spent at the site on the post-removal survey was almost double that of the pre-removal survey. Without the actual ‘fishing’ time being recorded accurately (i.e. the total amount of seconds the electrofisher is sending current into the water, or the amount of time a net is set), the total amount of fish captured at that site cannot be compared to any other results.
A well-designed survey requires that the survey method be implemented in a specific way and that various pieces of information be recorded. Points at the survey site should be identified and should be spread over the distance of the site; they should also include a representative of each habitat type present. These points are called ‘shots’. Electrofishing surveys are done in 50 m shots. Each individual net set or trap set is also a shot. The greater the number of shots, the more representative the catch is likely to be. However, there is a trade-off between what is ideal and what is practical given the time available to run a survey and the number of sites that need to be covered. For example, it may only be practical to do six 50 m electrofishing shots at a site and to set six fykes. All data collected from these shots should be recorded on a survey record sheet (an example of a pest fish survey record sheet can be found on page 68).
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When conducting backpack electrofishing, surveyors would typically walk up the creek holding the power on the backpack for 450–600 seconds (depending on the complexity of the environment) over the 50 m length of the shot, collecting fish that are affected by the current in a bucket. If nets are being used to survey the site, they would be deployed at a point within the 50 m shot (taking a GPS coordinate to enable redeployment at the same point during the next survey). The set and clear time of the net would be recorded so that total set time could be calculated.
The following information should be recorded if possible during each survey:• date• survey team members• river• site name• GPS point latitude and longitude of shot• method (i.e. electrofishing, fyke net)• shot number (1 to 6)• shot length (usually 50 m) if electrofishing• shot area if seining• fyke set width (if applicable)• water depth• width of river• electrofisher settings (if applicable)• electrofisher power-on time (if applicable)• net or trap set time (if applicable)• net or trap clear time (if applicable).
All captured fish are then identified and measured. A total count of each species should be recorded as well as the total length. Lengths of fish captured during surveys can give an insight into the population dynamics of a pest species. For example, for a sustained management intervention to be successful, a greater number of adult fish needs to be removed than new recruits in the population. Therefore, a reduction in the larger fish size classes would be recorded during the surveys over time.
Important information!Animal surveys conducted in Queensland that record information or are of a scientific nature may require the approval of an Animal Ethics Committee (AEC). Please contact a Queensland AEC or visit <www.dpi.qld.gov.au> for more information.
All surveys conducted in New South Wales require AEC approval. Please contact a New South Wales AEC or visit <www.dpi.nsw.gov.au> for more information.
Important information!An effective way for surveyors to target tilapia for capture is to exploit habitats within a waterbody that consist of the invasive wetland weed, para grass (Urochloa mutica). This is because tilapia are known to thrive in such habitats. Any para grass habitats present in the survey site should therefore be included in the survey design.
Figure 5.14 Area infested with para grass (Urochloa mutica)
Figure 5.15 Para grass (Urochloa mutica)
Module 5:Rapid response and survey techniques
Sam
ple
of a
pes
t sur
vey
reco
rd s
heet
MDB
sta
ndar
d sh
ot d
ata
Dat
e: _
____
____
__/
____
____
_/ _
____
____
_
Nam
es o
f sur
veyo
rs: _
____
____
____
____
____
____
____
____
____
____
____
____
____
____
____
____
____
____
____
_
Rive
r: __
____
____
____
____
____
____
____
____
____
_
Site
nam
e: _
____
____
____
____
____
____
____
____
_
Site
type
: Lag
oon
/ Ri
ver /
Ana
bran
ch /
Tri
buta
ry
GPS
poi
nt: L
at. _
____
____
____
_0
Long
. __
____
____
____
____
_0
Hyd
rogr
aphy
: Bas
e /
Rise
/ P
eak
/ Fa
ll /
No
flow
Fyke
cod
-end
: Ups
trea
m /
Dow
nstr
eam
Shot
num
ber:
___
____
____
____
__ S
hot l
engt
h (m
): __
____
____
__
Max
imum
dep
th (c
m):
____
____
___
Wid
th (m
): __
____
____
_ Fy
ke s
et ti
me:
___
____
___
pH
: ___
__
Riffl
e ru
n %
: __
____
____
____
___
Po
ol %
: ___
____
____
____
____
_ Co
nduc
tivi
ty (μ
S): _
____
____
____
__
Wat
er te
mp
(o C):
____
____
__
Fyke
che
ck ti
me:
___
____
____
__
Met
hod:
Bac
kpac
k /
Smal
l boa
t / L
arge
boa
t / F
yke
/ M
ini f
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S
ettin
gs:
volt
s ___
____
_%
gain
___
____
_pp
s __
____
___
BPS
___
____
___
Pow
er o
n tim
e (s
ec) _
____
___
Spec
ies
Coun
tLe
ngth
(cm
)
12
34
56
78
910
1112
1314
1516
1718
1920
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Case studies
State government surveillanceThe Queensland Government is tackling the state’s pest fish problem by giving priority to vulnerable catchments and hot spots within those catchments. Catchments identified as vulnerable include the Murray–Darling Basin (tilapia), the Gulf of Carpentaria (tilapia) and Lake Eyre (carp). The government investigates reports of new pest fish sightings made by the public and conducts ongoing surveillance surveys in hot spots to allow for early detection of pest fish incursions.
In 2006, New South Wales developed a Monitoring, Evaluation and Reporting (MER) Strategy to better understand changes in the overall health of natural resources. Surveillance for pest fish is conducted under the current MER Strategy (2010–2015), as well as other research projects, and involves comprehensive statewide monitoring of native and non-native species.
Cape Cleveland pest fish surveyIn 2001, a pest fish survey was conducted by the Northern Fisheries Community and Fishway Monitoring Team at a number of locations in the Cape Cleveland area, east of Townsville in North Queensland. The survey was conducted to verify reported occurrences of Mozambique tilapia and to determine the extent of the infestation and the chances of eradicating the species from this area. The area was considered high priority, as the study site drains into the lower section of the Haughton River, an area recognised as a barramundi breeding habitat.
As most of the area was heavily vegetated with dense weed growth and a poorly defined creek line, netting and trapping methods were considered to be too cumbersome and ineffective in this case. Therefore, electrofishing (both backpack and boat-mounted form) was used in conjunction with visual observations.
The backpack electrofishing method was found to be highly inefficient, due to some physiological factors specific to the species. Boat-mounted electrofishing was more effective, but tilapia were still hard to capture this way. Visual observation of tilapia in the water proved to be the most reliable method of tilapia detection.
Tilapia were detected in 10 of the 26 sites surveyed in the area. Tilapia were found alongside native fish fauna, with a higher diversity of native species being present in areas where tilapia were absent. Tilapia abundance was the highest in areas associated with weed beds and snag piles.
The survey acted as a starting point for the development of a management plan. It concluded that further investigation would be needed to determine whether eradication by poisoning was a possibility in this case.
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Module 5:Rapid response and survey techniques
Learning activitiesPest fish survey methods
Purpose: To help participants understand how to apply knowledge of pest fish survey methods to a real situation in a formal scientific manner.
Think of a section of creek in your local area and, as a group, design a survey plan to detect the presence or absence of tilapia. You will need to consider all possible survey methods available and make decisions based on the pros and cons of each technique for this particular case. Remember to implement a combination of several methods in order to get the best result. Justify your choice of methods. You should also design a data recording sheet for your survey that includes calculations to convert your data into statistics for interpretation and analysis.
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Quiz1. What are the three reasons for the use of
pest fish surveys?a) Control, eradication and monitoring/
evaluationb) Investigation, surveillance, monitoring/
evaluationc) Investigation, control and monitoring/
evaluationd) Education, eradication and evaluation
2. Which of the following statements is true?a) Contrary to what is suggested by its
name, electrofishing does not involve electricity
b) Non-fish fauna are not affected by electrofishing
c) Electrofishing causes fish to involuntarily swim towards the anode
d) Electrofishing results in the fish being electrocuted, allowing for easy collection of the dead fish
3. Which of the following is not used for pest fish surveys?a) Seine netsb) Fishing rodsc) Funnel trapsd) Fish poisonse) Snorkels
4. Which of the following survey methods does not require a general fisheries permit or a collection permit?a) Seine netsb) Electrofishingc) Cast netsd) Line fishing
5. Fish surveys conducted in Queensland that record information or are of a scientific nature may require approval by:a) The Prime Ministerb) An Animal Ethics Committeec) The head surveyord) The person who first discovered the
pest fish in question
Answers
1. b) Investigation, surveillance, monitoring/ evaluation
2. c) Electrofishing causes fish to involuntarily swim towards the anode
3. d) Fish poisons
4. d) Line fishing
5. b) An Animal Ethics Committee
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Module 5:Rapid response and survey techniques
How do I pay my recreational fishing fee for fishing in New South Wales?New South Wales recreational fishing fees can be paid online at <www.dpi.nsw.gov.au>, by calling 1300 369 365, from fishing fee agents (listed online) or from most Kmart stores in New South Wales.
Is it possible to organise some in-field training for some of the survey techniques?This may be possible; for information please contact DEEDI on 13 25 23 or send an email to [email protected].
FAQsHow do I apply for a general fisheries permit or a collection permit?For a Queensland general fisheries permit, contact DEEDI on 13 25 23 or fill out a permit application online by visiting <www.fisheries.qld.gov.au>.
For a NSW collection permit contact NSW DPI on (02) 4982 1232 or fill out a permit application online at <www.dpi.nsw.gov.au>.
Can recreational anglers target tilapia?Tilapia may be captured during recreational fishing; however, their possession in Queensland is illegal. Therefore, any tilapia captured must be euthanised and disposed of straightaway. The most humane way of euthanising is to stun the fish with a sharp blow to the head just above the eyes, causing brain destruction. It can be disposed of in an appropriate rubbish bin or buried well away from the water. The most important things for recreational anglers to remember are not to use tilapia as bait, alive or dead, and not to release tilapia back into a waterway, as viable eggs/larvae may be present in the fish’s mouth.
