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Animal Sciences Group
Aquaculture and Fisheries Group De Elst 1 6708 WD Wageningen
The Netherlands Tel: +31 (0) 317 483307 Fax: +31 (0) 317 483962
Name: Imke van Gerwen
Reg.nr. 880410259040
MSc Thesis nr. T 1914 THESIS
December 2013
AQUACULTURE AND FISHERIES GROUP
LEERSTOELGROEP AQUACULTUUR EN VISSERIJ
The effects of trap fisheries on the populations of
Caribbean spiny lobster and reef fish species at the
Saba Bank
Abstract:
The Caribbean spiny lobster (Panulirus argus) is a widespread crustacean species. It inhabits shallow
water reefs and rocky substrates from Brazil to Florida. The lobster fishery is one of the most
important fisheries in the Caribbean (in 2011 the total catch was 35,642 tons), generating more than
456 million US dollars annually. However, the annual landings of P. argus throughout the Caribbean
have been in decline since 1995 (FAO, 2013). Over-exploitation is thought to be one of the major
causes of this decline (CRFM, 2011).
One of the areas where the spiny lobster fishery is important, is on the Saba Bank, a 2,200 km2
submerged plateau, near Saba in the northern Caribbean Sea. Spiny lobsters are fished exclusively
with traps by nine small (11m) vessels operating from Saba. To determine the current status of the
P.argus stock and its fishery on the Saba Bank, basic fisheries data were collected in 2012 and
compared with similar studies conducted in 1999 and 2007.
The number of lobster traps hauled per fishing trip increased from 59 to 80 between 1999 and 2012
while the number of lobsters landed per trip decreased from 83 to 52 per trip during the same
period. A similar declined was observed in the standardized (75 trap hauls per trip) CPUE both in
number and total weight of lobster landed. No obvious changes in fishing areas on the Saba Bank
were observed during this period.
The total catch of lobster was estimated as 62 t, 92 t and 38 t in 1999, 2007 and 2012, respectively.
The high catch in 2007 was attributed to the higher number of estimated fishing trips in 2007 (1000)
compared to 1999 (650) and 2012 (600). The lower estimated annual catch in 2012 compared to
1999 is attributed to a decline in CPUE. These result suggest a decrease in abundance of spiny
lobster on the Saba Bank between 1999 and 2012, similar to decline observed in the wider
Caribbean.
Size-at-maturity (CL50%) for male P.argus was found to be 92.2 (± 2.53 SE) mm carapace length,
slightly below the minimum legal size (95mm CL). The mean size of landed male (109 mm CL) and
female lobster (105 mm CL) showed that predominantly large, mature lobster are landed. Berried
female spiny lobsters were observed on the Saba Bank throughout the year with a peak from March
to June.
In addition to lobster, mixed reef fish were also landed in the lobster trap fishery. A total of 57 fish
species were identified in the catches. Roughly 15 kg of mixed reef fish was landed per lobster trip,
resulting in an estimated 8-10 t of mixed reef fish landed in 2012. The species composition (in
weight) of the landed mixed fish consisted mainly of grunts (Haemulon album, H. melanurum and H.
plumierii 30%), small groupers (Epinephelus guttatus and Cephalopholis fulva 17%) and queen trigger
fish (Balistes vetula 21%). Only the mean total length of landed E. guttatus decreased significantly
between 1999 (33 cm TL) and 2012 (31 cm TL).
In addition to the landed mixed fish, an estimated 10 t of mixed fish was discarded in 2012. The
species composition (in weight) of the discarded mixed fish consisted mainly of grunts (H. melanurum
and H. plumierii 34%), boxfishes (Acanthostracion quadricornis and A. polugonia 19%) and nurse
sharks (Ginglymostoma cirratum 9%).
2
Contents
Abstract………………………………………………………………………………………………………………………………………………3
1. Introduction…………………………………………………………………………………………………………………………………4
2. Literature review………………………………………………………………………………………………………………………….7
2.1 Life history and biology of P. argus……………………………………………………………………………………..7
2.1.1 Distribution & abundance………………………………………………………………………………….7
2.1.2 Lobster as a predator………………………………………………………………………………………..7
2.1.3 Lobster as prey………………………………………………………………………………………………….7
2.1.4 Planktonic larval state (phyllosoma)………………………………………………………………….8
2.1.5 Post-larval state (pueruli)………………………………………………………………………………….8
2.1.6 Juvenile state…………………………………………………………………………………………………….9
2.1.7 Adult state………………………………………………………………………………………………………10
2.2 Caribbean P. argus fisheries and management…………………………………………………………………12
2.2.1 Caribbean fisheries………………………………………………………………………………………….12
2.2.2 Population monitoring…………………………………………………………………………………….13
2.3 Biodiversity on the Saba Bank…………………………………………………………………………………………..14
3 Materials & Methods………………………………………………………………………………………………………………….15
3.1 Study site………………………………………………………………………………………………………………………….15
3.2 Study design……………………………………………………………………………………………………………….…….15
3.2.1 Fishing trip log…………………………………………………………………………………………………16
3.2.2 Short interview………………………………………………………………………………………………..17
3.2.3 Long interview…………………………………………………………………………………………………18
3.2.4 On board measuring……………………………………………………………………………….……….18
3.2.5 Carapace length………………………………………………………………………………………………19
3.2.6 Sex…………………………………………………………………………………………………………………..19
3.2.7 Tar spot & Berried females………………………………………………………………………………20
3.2.8 Merus length…………………………………………………………………………………………………..20
3.2.9 Size at maturity males……………………………………………………………………………………..21
3.2.10 Ecdysis…………………………………………………………………………………………………………….21
3.2.11 Mixed fish species composition………………………………………………………………………21
3.2.12 Fork length and Total Length ………………………………………………………………………….21
3.3 Statistical analysis…………………………………………………………………………………………………………….22
3.3.1 Standardization of CPUE………………………………………………………………………………….22
3.3.2 CPUE weight per standardized trip………………………………………………………………….23
3.3.3 Comparing of means……………………………………………………………………………………….23
4 Results……………………………………………………………………………………………………………………………………….24
4.1 Effort………………………………………………………………………………………………………………………………..24
4.2 Catch…………………………………………………………………………………………………………………………………25
4.3 Standardized CPUE……………………………………………………………………………………………………………26
4.4 Length-frequency …………………………………………………………………………………………………………….27
4.4.1 Landed…………………………………………………………………………………………………………….27
4.4.2 Discarded versus landed catch………………………………………………………………………..27
4.5 Reproductive biology.……………………………………………………………………………………………………….30
4.5.1 Females…………………………………………………………………………………………………………..30
3
4.5.2 Males………………………………………………………………………………………………………………30
4.6 Mixed fish…………………………………………………………………………………………………………………………31
4.6.1 Species composition.….……………………………………………………………………………………31
4.6.2 Length-frequency…………………………………………………………………………………………….31
5 Discussion…………………………………………………………………………………………………………………………………..37
5.1 Lobster…………………………………………………………………………..…………………………………………………37
5.1.1 Catch, effort, CPUE………………………………………………………………………………………….37
5.1.2 Length-frequency…………………………………………………………………………………………….38
5.1.3 Reproductive data…………………………………………………………………………………………..39
5.2 Mixed fish…………………………………………………………………………………………………………………………40
6 Conclusion………………………………………………………………………………………………………………………………….42
7 Reference list……………………………………………………………………………………………………………………………..43
Appendix
Acknowledgements
I would like to thank my supervisors Dr. Martin de Graaf and Dr. Leo Nagelkerke for giving me the
opportunity to do this internship and fieldwork on one of the most beautiful places on earth. This
research was financed by BO-11-011-05-008.
I also want to thank the fishermen and deck hands for their cooperation and taking me on board.
Without them I could not have done this research. Special thanks go to: Ivan Hassell, Craig Hassell,
Augustino Hassell, Michelle Peterson, Wes, Julian Hassell, Randall “China” Zeegers, Kenneth Johnson,
Roley Levinstone, Walter Hynds, Nicky Johnson, Ryan Hassell.
Michelle Boonstra, thank you for helping me with my sampling sessions at the harbor.
I would like to thank the Saba Marine Park, Kai Wulf, Gregoor van Laake, and Keith Murphy for
accommodating me and help me with technical issues. Wouter van Looijengoed, thank you for
helping me with the monitoring of the larval collectors.
I am very grateful of Professor Simon de Lestang for helping me with the analysis of the size at
maturity for male P. argus. Last but not least I would like to thank Professor Mark Butler for giving
me advice and lectures on P. argus.
4
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
Cat
che
s (t
)
Fig. 1. Total landings (t) of Panulirus argus in the Caribbean (FAO, 2013)
1. Introduction
The use of marine resources has increased over the past hundred years due to the growth of the
world’s human population and the improvement of technology (Ault et al., 2013; Cadigan, 2001).
Recently the focus on the management of these resources has intensified, due to the decline of fish
stocks and the loss of habitat worldwide (Beddington et al., 2007; Pauly, 2009; Worm et al., 2006; Ye
et al., 2013). One of the marine resources of which catches have decreased over the past decade is
the Caribbean spiny lobster
(Panulirus argus; Latreille, 1804)
(FAO, 2013). In the Caribbean this
species is one of the main
targeted marine resources (CRFM,
2011). Due to increased tourism in
the Caribbean (and specifically the
Dutch Caribbean) the demand for
spiny lobster has risen in the past
decades (Dilrosun, 2000).
However, in 2011 a total of 35,642
tons of lobster have been landed
(FAO, 2013) (fig. 1) which is a
decline of 15 % compared to the
landings of 1995. The decline of
the landings of P. argus is
generally assumed to be caused
by intensified fishery (CRFM,
2011).
The Saba Bank, a large submerged plateau near Saba, is an important fishing ground for the Saban
inhabitants (Dilrosun, 2000; Toller & Lundvall 2008), and has been for the surrounding Islands. Until
the Netherlands Antilles fishery law became effective in 1993, many foreign vessels fished on the
Saba Bank (Guidicelli & Villegas, 1981; Dilrosun, 2000; Hoetjes & Carpenter, 2010). Since the
implementation of the law foreign vessels were prohibited to fish for lobster in the Exclusive
Economic Zone (EEZ) of Saba (Hoetjes & Carpenter, 2010).
Nowadays, the spiny lobster fishery is the most important fishery on the Saba Bank (Lundvall, 2008)
with an estimated ex-vessel revenue of $ 1.3 million US dollar per year (based on total landings of
83600 kg lobster)(Toller & Lundvall, 2008). This is less than 1 % of the total tons of lobster landed in
the Caribbean annually. On Saba, a total of ten fishing licenses are issued to the commercial lobster
fishery (Dilrosun, 2000; Lundvall, 2008) and ca. 30 people generate a living from this fishery
(Dilrosun, 2000).
5
Besides lobster, deep-water snapper species or “redfish” are commonly caught by Saban fishermen.
Because of the difference in fishing method, i.e. different type of bait and traps deployed at greater
depths, this fishery is considered independent (Toller & Lundvall, 2008) and will therefore not be
addressed in this thesis. The Saban fishermen,
fishing for lobster, deploy their traps on shallow
areas of the bank, preferably near rocky substrate or reef structures. These areas are mostly situated
along the edge of the Saba Bank, nearest to the Island of Saba (Toller & Lundvall, 2008). Some
fishermen fish farther on the bank but do not go below depths of 45 meters. This means that 84 % of
the Saba Bank is potentially suitable for lobster fisheries (Toller & Lundvall, 2008). The vast majority
of the catch is sold to the neighbouring Island St. Maarten, the rest of the lobsters is distributed to
other Caribbean islands (Dilrosun, 2000).
The most commonly used trap to catch spiny lobster is the arrowhead trap with a single funnel
(fig.2a+b) (Dilrosun, 2000). The traps are baited with salted cow hides (20 x 20 cm), which are
attached to the traps with coated wires (Toller & Lundvall, 2008). All traps are provided with an
escape panel, a trapdoor on the side of the trap that is fastened with wire, which is both convenient
to get lobsters out of the traps but it is also mandatory.
There are several regulations on the fisheries that are enforced by the Coast Guard to insure
sustainable exploitation of the P. argus population (Dilrosun, 2000). The escape panel, for example,
has to be biodegradable, to minimize the effects of “ghost traps” (Dilrosun, 2000). Another
requirement is that the mesh size of the traps should be no less than 3.8 cm or 1.5 inch (Dilrosun,
2000). Also, it is not allowed to land egg-bearing females or moulting specimen and the minimum
carapace length (CL) of the lobsters is 95 mm (Dilrosun, 2000).
Although the lobster fisheries on the Saba Bank target spiny lobster, it is common that also shallow
water reef fish species are harvested and landed both for commercial benefits and to serve as food
for the spiny lobsters in their holding pots (Toller & Lundvall, 2008). The three fish species that are
Fig. 2a. Arrow head lobster trap. (I van Gerwen 2012).
Escape panel
61
cm
(2
fee
t)
Fig.2b. Arrowhead lobster trap (122x122x61 cm) range of width (91-152 cm),
with a single funnel (w23 x h20 cm) and an escape panel.
6
landed most are: the Haemulon plumierri (White grunt), Balistes vetula (Queen Triggerfish) and
Epinephelus guttatus (Red hind) (Dilrosun, 2000; Toller & Lundvall, 2008). The ex-vessel value of the
total bycatch annually has been estimated at $ 68,700 US dollar (Toller & Lundvall, 2008). Although
this amount is a fraction of the value of landed lobster per year, because of its economic benefits this
bycatch will be quantified. Because of the variety of fish species that are caught the bycatch, both
discarded and landed, will be referred to as “mixed fish” throughout this thesis.
In 2008 a management plan for the Saba Bank was presented. One of the main goals is the
protection and maintenance of biodiversity and natural resources on the Saba Bank (Lundvall, 2008).
To accomplish sustainable use of marine resources on the Saba Bank, long-term monitoring of the
fisheries is essential, to develop target and reference points for indicators, such as catch per unit
effort (CPUE) and average length (Beddington et al., 2007; Lundvall, 2008; Hoetjes & Carpenter,
2010). Two extensive assessments have already been carried out on state of fisheries by Dilrosun
(2000) and Toller & Lundvall (2008). However, compared to other well researched lobster species
stocks i.e. Western rock lobster Panulirus cygnus (Hancock, 1981; De Lestang, 2006; Department of
Fisheries Western Australia, 2013), the quantity of data on the P. argus population on the Saba Bank
is limited. Simple robust quantifiable objectives and reference points are missing. Therefore, the aim
of this study is to obtain data to estimate the current status of the P.argus stock, as well as to provide
a baseline for research in the future. Because the lobster fishery also harvests “mixed fish”, this
research will not only investigate the effects of lobster trap fisheries on the P. argus population, but
it will also investigate the effects on reef fish species.
To reach this goal the following questions will be answered:
- What is the status of the Panulirus argus population on the Saba Bank in 2012 compared to
2000 and 2007?
- What effects do lobster trap fisheries have on both the Panulirus argus population and the
reef fish population on the Saba Bank?
These questions will be addressed by analysing changes in catch per unit of effort (CPUE) of the
fisheries between years and by analysing biologically relevant data such as length frequency, size at
maturity, species composition.
7
2. Literature review
In order to define the status of the Panulirus argus population on the Saba Bank, information is
needed about the biology and factors that influence population dynamics of this species. Therefore,
in this review I am going to treat the life history of P. argus. Also lobster fisheries and management
throughout the Caribbean are covered. At the end I will focus shortly on the Saba Bank for it is the
study site of this research.
2.1 Life history and biology of P. argus
2.1.1 Distribution and abundance
The Caribbean spiny lobster (Panulirus
argus) is an abundant and
widespread, crustacean that belongs
to the order of Decapoda and family
of Palinuridae. The family of
Palinuridae consists of 12 genera
containing 59 species (Zhang, 2011).
Other spiny lobster species which can
be found in the Caribbean are
Panulirus guttatus (Spotted spiny
lobster) and Justitia longimanus (Red
banded lobster) (Humann & Deloach,
2002) Genetic evidence indicates that
P. argus is part of a pan-Caribbean
population, which stretches from
Bermuda to Brazil (Silberman et al.,
1994) (fig. 3). The offshore
distribution of P. argus larvae
contributes to the homogenization
of genetic material throughout the
Caribbean and the recruitment of
lobster stocks in remote areas (Yeung
& McGowan, 1991). This species of
lobster is predominantly found in shallow coastal areas down to depths of 90 m (Holthuis, 1991).
2.1.2 Lobster as predator
Panulirus argus is a predator and its diets changes during ontogeny (Briones-Fourzán et al., 2003; Cox
et al., 2008). In the early juvenile stages (10-15 mm CL) only small and soft prey (1-2 mm in
diameter), are preyed upon (Briones-Fourzán et al., 2003; Cox et al., 2008). During development (15-
44 mm CL) larger and tougher prey is consumed (2-5 mm in diameter). A large overlap in type of prey
is found in the juvenile stages, prey consists mainly of crustaceans and mollusks, such as hermit
crabs, true crabs (Brachyura), and gastropods (Briones-Fourzán et al., 2003; Cox et al., 2008). Besides
the previous mentioned organisms also plant material has been found to be part of juveniles’ diet by
analyzing gut contents (Briones-Fourzán et al., 2003). Prey of late juvenile (45-80 mm CL) stages and
Saba Bank
Fig. 3. Distribution of Panulirus argus. Adjusted after FAO 2013
8
adults consists of crustaceans, echinoderms and mollusks, mainly gastropods but also bivalves and
chitons (Lozano & Alvarez, 1996; Cox et al., 1997; Cox et al., 2008).
2.1.3 Lobster as prey
Natural predators of P.argus are nurse sharks (Ginglymostoma cirratum), triggerfish (Balistidae)
groupers (Serranidae) and other large finfish (Lavalli & Herrnkind, 2009). Also octopuses have found
to prey on P. argus (Berger & Butler et al., 2001). To avoid predation larger juveniles (>15mm CL) and
adult P. argus hide in crevices during the day. At night when the lobsters leave their shelters and they
feel threatened, they swim away by strongly flapping their tail (Humann & deLoach, 2002). Another
defense mechanism is the parrying of predators with their spiny antennae (Lavalli & Herrnkind,
2009). Also the aggregation of adult lobsters into large groups has shown to increase survival rate
(Lavalli & Herrnkind, 2009).
The life history of P. argus can generally be divided in four stages namely the planktonic larval, post-
larval, juvenile, and adult stage. Next the developmental stages will be covered.
2.1.4 Plankton larval stage (Phyllosoma)
Little is known about the planktonic larval stage of P. argus (fig.
4) because the larvae occur in low concentrations far offshore
(Goldstein et al., 2008). In this stage the body of the lobster is
flattened and it has long legs (fig.4) which is appropriately
named phyllosoma meaning “leaf like body”. What is known is
that, the planktonic larval stage undergoes ten metamorphosis
phases (Goldstein et al., 2008; Lewis, 1951). Body lengths of the
phyllosomata range from 1.6 – 27 mm depending on the phase
they are in (Goldstein et al., 2008). Another feature that makes
the research on this developmental stage harder is the duration
of the larval stage. Estimates range from six months to more
than a year (Goldstein et al., 2008; Lewis, 1951; Phillips &
McWilliam, 1986). Also, during the planktonic stage the larvae
migrate vertically through the water column, which adds to the
complexity of the distribution of this developmental stage of P.
argus (Yeung & McGowan, 1991). Taking into account
ontogenetic vertical migration (OVM), diurnal vertical migration
and the long larval stage of P. argus the distance between the
spawning and settlement area of larvae has been estimated to reach up to 400 km (Butler et al.,
2011). The dispersal model also showed a maximum dispersal of approximately 1,000 km. This
indicates that a part of the larvae (~60%) settle close to the adult population; the so called “self –
recruitment” (Butler et al., 2011). The other part (~20%) contributes to long distance dispersal of P.
argus (Butler et al., 2011).
Fig. 4. Phyllosomata of P. argus.(1.6-27mm) (UNC)
9
Post- larval stage (puerulus)
When the planktonic larvae undergo
their last metamorphosis they
transform in a shape that is more
recognisable as an adult spiny lobster
(fig. 5). This stage is called “puerulus”
which means “little boy” with a
carapace length of 5-9 mm (Cox et al.,
2008). The actual metamorphosis
occurs far offshore close to the
continental shelf (Phillips & Williams,
2008). This stage is called puerulus and
only lasts three to four weeks. In this
stage the puerulus does not feed (Cox
et al 2008) and swims towards the shore, mostly on the surface at night during new moon flood tides
to decrease predation pressure (Acosta et al., 1997; Acosta & Butler, 1999). Upon arrival, the pueruli
settle in structurally complex hard-bottom habitats that have abundant, preferably red, macroalgae
vegetation (Marx and Herrnkind, 1985; Herrnkind & Butler, 1986; Field and Butler, 1994). The
physical and chemical cues that the pueruli respond to for the migration into nursery areas are
poorly understood. It is suggested that the metabolites of red algae in nurseries attract the pueruli
and enhance their settlement into coastal habitats (Goldstein & Butler, 2009).
2.1.5 Juvenile stage (10 - ± 80 mm CL)
Approximately 15 days (Goldstein et al., 2008)
after the settlement in the nurseries, the
transparent pueruli of P. argus get more
pigmented and their flattened body shape
transforms into more cylindrical shaped juvenile
stage (fig. 6). Juveniles are solitary living and their
camouflaged bodies blend well in the algal
substrate of the nursery habitat where they stay a
couple of months until they reach 17 mm CL
(Herrnkind & Butler, 1986, Marx & Herrnkind,
1985). Although the juveniles in the nurseries are
sheltered from predators and food is abundant
(Marx & Herrnkind, 1985) mark and recapture
studies show that in the first couple of months only 2-4 % of the settled lobsters survive (Butler et al.,
1997).The mortality rate of the juveniles is negatively related to the number of shelter crevices in the
nursery habitat (Butler et al., 2001). When the juveniles reach a carapace length of 15 mm, they
migrate from the algal vegetation towards the crevices that are mainly provided by sponges where
they reside during daytime (Forcucci et al., 1994, Butler et al., 1995, Herrnkind et al., 1997). During
nighttime these juveniles leave their shelters, where the distance they cover increases with
Fig. 5. Transparent P.argus puerulus. (M. Butler et al., 2010). Size: 5-9 mm CL
Fig. 6. Juvenile of P. argus 12 mm CL (I. van Gerwen 2012)
10
maturation. After one or two years the juveniles leave the nurseries and move towards deeper lying
areas further offshore (Butler et al., 2011).
2.1.6 Adult stage
When the lobsters reach their adult
stage (fig. 7) in 2-3 years (Maxwell et
al., 2013) they change from solitary to
social animals. They more often
aggregate in shelters and with
increasing length natural mortality
declines (Eggleston et al., 1990; Smith
& Herrnkind, 1992), because they have
more effective anti-predator responses
(Briones-Fourzán, 2006). Also the
larger the lobsters grow the less
predators can physically prey upon
them, because the lobsters then do not
fit in their mouths (Nilsson &
Bronmark, 2000). On the other hand
fishing mortality increases with body size (Phillips & Kittaka, 2001). The growth rate of the lobsters
decreases with carapace length (Erhardt, 2008). It is estimated that the lobsters can reach 20 years of
age (Maxwell et al., 2007).
Reproduction
When female and male P. argus reach their adult phase they look for a suitable mating partner. In
pristine ecosystems, the mating system of the Caribbean spiny lobster resembles a lek system, where
one big male has a harem of females and defends his territory (George, 2005). During courting the
males caresses the body of the females with its long legs which enables them to assess the size of the
females (George, 2005). Then the male places a sperm package on the abdomen of the female, which
is called a “tar spot” (George, 2005). The size of the spermatophoric mass (tar spot) that a male
deposits, depends both on the size of the male as well as the size of the female (MacDiarmid &
Butler, 1999). The female produces rows of eggs and keeps them on the ventral side of the abdomen.
She then scratches the sperm package open with her hind legs and transfers the sperm to the eggs.
After the eggs have been fertilized they are retained until they are all ready to hatch. The eggs are all
simultaneously released upon hatching and a cloud of phyllosoma larvae is released into the water
column. Spawning peaks in the spring from March to June (Bertelsen & Mathews, 2001). In areas
closer to the equator it has been found that part of the adult population spawns throughout the year
(Butler et al., 2009). An overview of size at maturity, fecundity and spawning season is found in table
1.)
Fig. 7. An adult male P.argus finds shelter in a crevice (>80 mm CL). (I. van Gerwen
2012)
11
Reproductive characteristic
Reference
Size at maturity –
CL50%
- Female: 86.0±5.1 SD mm CL;
Male: 97.4±5.0 SD mm CL
(Bermuda, UK)
- Female: 81 mm CL (Cuba)
- Female: 93 mm CL (Turks &
Caicos Islands)
- Female: 92 mm CL (Colombia)
- Evans et al. 1995
- Evans et al. 1995
-
- Cruz & Léon, 1991
- Medley & Ninnes, 1997
- Gallo et al., 1998
Fecundity – Clutch size - 0.3 - 0.8 million eggs/clutch
(Florida Keys, FL, USA)
- 147,00 – 1,952,000 eggs/clutch
- Bertelsen & Matthews
2001
- Cox et al. 1997
Spawning season - March – June (Florida, US)
- March-May (Cuba)
- Throughout the year
- Bertelsen & Matthews
2001
- Cruz & Léon, 1991
- Butler et al., 2009
Table 1. Overview of size at maturity, fecundity and spawning season of P.argus in the Caribbean
12
2.2 Caribbean P. argus fisheries and management
2.2.1 Caribbean Fisheries
The P. argus fishery is one of the commercially most important fisheries in the Caribbean.
Throughout the Caribbean P. argus is fished upon with several fishing techniques, ranging from
catching the lobsters by hand by SCUBA divers to hundreds of baited traps hauled by boats that are
equipped with state–of the art devices, such as fish finders, GPS, depth sounder etc. Over 456 million
US dollars are generated with the fisheries on P. argus annually (Ehrhardt, 2005; CRFM, 2011).
Approximately 50,000 lobster fishers are active in the industry, and another 200,000 people that are
working in the lobster fisheries related jobs (FAO, 2003). Brazil, the Bahamas and Cuba are the three
top countries landing most lobsters annually (fig. 8).
The lobsters are sold alive, as a whole, or only the abdomen is frozen or canned (FAO, 2013). With
the industrialization of the fisheries the total landings of the lobsters increased steeply in the
Caribbean from 2,957t in 1950 to 42,519 t in 1996 but then levelled off, and in the past 5-10 years
the landings show a declining trend (FAO, 2013) (fig. 1). This decline has been consistent throughout
the Caribbean and because of the economic importance of this species, it has been stressed that
monitoring and enforcement of regulation is necessary to protect the stocks from overexploitation or
even collapse.
Many P. argus stocks (40%) throughout the Caribbean are considered to be overexploited, 7 out of
18 countries (CRFM, 2011). Therefore, countries have formed management plans and rules and
regulations are enforced locally (appendix A). One common regulatory measure is the closing of the
fishing area for a predetermined amount of months, often coinciding with spawning season. Other
Bahamas 24%
Brazil 21%
Cuba 19%
Nicaragua 12% U.S.A
6% Dominican Republic 4%
Honduras 3%
Mexico 2%
Haiti 2%
Venezuela 2%
Belize 2% Jamaica
1% Colombia 1%
Turks and Caicos Islands
1%
Puerto Rico 0%
Saba 0%
Fig. 8. Top 15 countries harvesting P. argus, as measured by average annual landings from 2000-2007 inclusive and Saba, and the
percentage of the total average landings (34, 664 t) by all countries over the same period of time (adapted from CRFM, 2011)
13
measures are the size limits and restrictions on the landing of moulting or berried females (carrying
eggs). The previously mentioned measures are also in place in the management of the P. argus stock
on the Saba Bank, an area that has not been covered in the CRFM review. However, due to the
aforementioned connectivity of the Caribbean spiny lobster population, management of the stocks is
an international problem. This makes the effectiveness of the management measures difficult to
quantify.
2.2.2 Population monitoring
With artificial collectors (fig. 9), the supply of post-
larvae of several spiny lobster species, have been
monitored (Butler et al. 2010; Gonzalez & Wehrtmann,
2011). By monitoring the recruitment over a longer
period of time (several years) studies have shown that
it is possible to predict stock size and/or catch of the
adult population a couple years later (Hancock, 1981;
Phillips, 1986; Lozano et al.; Cruz et al., 1993). To
predict the stock size of P. argus on the Saba Bank a
recruitment monitoring program was set up at the
coast of the Island Saba, a protocol for the monitoring
is provided in Appendix B.
Fig. 9. Recruitment collector deployed near Saba (I. van
Gerwen, 2012) (60x40x40 cm)
14
2.3 Biodiversity on the Saba Bank
Recently assessments on biodiversity of marine organisms have been performed on the Saba Bank
(Hoetjes & Carpenter, 2010). The Saba Bank is a 2,200 km2 submerged plateau. At the fringes of the
plateau, coral growth is more pronounced. Together with other rocky substrate it forms a habitat
that provides food and shelter for a great variety of marine organisms, including fish and
crustaceans. On this “fore-reef”, the habitat complexity is high, resulting in highest fish biodiversity
(Toller et al., 2010). Further towards the middle of the Bank, the habitat complexity decreases and
with it the biodiversity. In the more shallow parts of the Bank the Caribbean Spiny lobster finds its
habitat. Also large predators are found on the bank, for example nurse and reef sharks, groupers and
barracudas (Williams et al., 2010). During the winter months marine mammals like baleen whales
and several dolphin species are spotted at the edges of the Bank (Lundvall, 2008).
It is suggested that the lack of nursery areas, i.e. sea grass beds or mangroves, and the isolated
location are limiting factors to the fish biodiversity on the Saba Bank (Toller et al., 2010).
Nevertheless, 270 fish species have been recorded on the bank, which is an intermediate number
compared to other studies on reef fish biodiversity (123-517 fish species) (Williams et al., 2010). Also,
45 sponge species, 48 Gorgonian octocoral species and 320 macroalgal species have been
documented (Littler et al., 2010; Williams et al., 2010; Etnoyer et al., 2010; Thacker et al., 2010).
Because the species count did not reach its asymptotic phase, it is expected that the number of these
species on the Saba Bank will even be higher.
Because of this species richness the International Maritime Organization designated the Saba Bank as
the world’s 13th Particular Sensitive Sea Area in 2012. When, in 2010, Saba became part of the Dutch
territory the Saba Bank received the status of an official National Marine Park.
Trap fisheries in the Caribbean have been found to cause over-fishing, biodiversity loss and alteration
of ecosystem structure (Hawkins et al., 2007). Although lobster fisheries mainly target lobsters, with
the traps also shallow water reef fish are caught (Dilrosun, 2000; Toller & Lundvall 2008). Lobster
fisheries have been suggested to affect the biomass distribution of reef fish on the Bank (Toller et al.,
2010). Fish abundance and assemblage on different parts of the Saba Bank was compared based on
reef structure. Biomass and density of reef fish was lower on the fore reef than on reef flat habitat
(Toller et al., 2010). This was not expected because the fore reef was of higher habitat complexity
than the reef flat habitats. Species richness on the Saba Bank, on the other hand, was highest in fore
reef areas (Toller et al., 2010). Fish abundance and diversity has found to be positively correlated
with habitat complexity (Dominici-Arosemana & Wolff, 2005). Other factors that have been found to
affect or have the potential to affect the biodiversity and abundance of organisms on the Saba Bank
are coral bleaching, invasive species i.e. Lion fish; oil spills from neighbouring islands; the loss of traps
due to hurricanes or strong tropical storms; and anchoring of large ships on the Saba Bank (Lundvall,
2008).
15
3. Material and Methods
3.1 Study site
The Saba bank (17025' N, 63030' W) is one of the largest submerged atolls in the world with an
estimated surface area of more than 2,200 km2. It is located 3 – 5 km southwest of the island of Saba
and 25 km West of St. Eustatius (Hoetjes & Carpenter, 2010) (fig. 10). The average depth of the Bank
is 25m, but the shallowest parts in the north and northeast are only 11-13 m deep, from where the
bottom slowly slopes down towards the west. The edges of the bank are quite steep, dropping in
some areas from 11-20m to >500m depth. The term atoll is given to the Saba Bank because of the
presence of corals on the Banks edges creating a reef structure that forms a circle around a lagoon
zone where corals are virtually absent (Toller et al., 2010). The Saba Bank is likely to have a volcanic
core.
3.2 Study design
To determine the status of the P. argus stock on the Saba Bank, catches were monitored over a
fieldwork period of five months (July-November 2012). Basic fisheries catch and effort data was
obtained through standardized short interviews. The catch and effort data was compared to the
assessments of 1999 and 2007. Also, biological data was obtained through sampling of both landed
and discarded catches. This data was collected to estimate the size at maturity and length frequency
of P. argus on the Saba Bank as well as to determine fish species composition and length frequency
Fig. 10. Location of Saba Bank in the Caribbean. (Hoetjes & Carpenter 2010) doi:10.1371/journal.pone.0010769.g001
16
distribution. Monitoring landings alone creates a skewed view on fisheries effects, because in case of
the Saba Bank fishery, a size limit is set for the lobsters landed at the harbour. This will result in a
biased estimate of the selectivity of the traps. Therefore, we decided to quantify discards because
this could give us valuable information on the effect of fisheries on both P. argus and reef fish
populations. With the results of the on-board trips we wanted to validate the importance of discard
monitoring, because the measuring of discards is labour intensive (you have to go on-board, this
takes a day per trip).
The research consisted of both port sampling and on-board sampling of both P. argus and mixed fish
species using the following procedures:
1. Fishing trip log (every day) to collect effort data.
2. Short interviews (66 % of fishing trips) to collect catch and effort data.
3. Long interviews (17.2 % of lobster trips) to collect biological data
4. On-board sampling (9 trips in total) to collect biological data
Lobster
Port sampling On board sampling
Carapace length (CL)
Sex
Tar spot
Merus length (of some male lobsters)
Carapace length (CL)
Sex
Tar spot
Berried
Moulting
Merus length (all discarded male lobsters)
Mixed Fish
Of 27 landed catches and all the discarded catches (9) species composition was recorded. Fish was
identified on the species level. Length data was measured to the nearest cm.
3.2.1 Fishing trip log
In order to obtain a good indication on the fishing intensity and effort on the Saba Bank, every fishing
trip was logged (fig. 11). This meant that every morning the presence or absence of the fishing boats
was monitored. Sometimes fishermen used their boats for purposes other than fishing (i.e. buying
bait or visiting neighbouring Islands). These trips were not logged. On rare occasions fishermen hired
boats (and crew) from other fishermen to haul their traps, because their own boat was out of the
water for repair. In this case the boat that belonged to the owner of the traps was logged instead of
the boat that was hired, this way the trip frequency per boat can be estimated more accurately. An
Table 2. Biological data obtained with “long interviews” at the harbor and with on board sampling
17
average number of trips per day,
for the five months the trips
were logged, was calculated and
extrapolated to average fishing
trips per year, so this could be
compared with previous
assessments. With the short
interviews the percentage of
fishing types (lobster, redfish,
long lining etc.) of the total trips
has been calculated. With the
estimated total fishing trips per
year and the percentage that is
accounted per fishing type the
number of lobster fishing trips
has been calculated.
A total of 377 trips were logged in July-November 2012. Data obtained:
- Number of fishing trips per day
3.2.2 Short interview
The duration of short interviews was approximately 5 min in which fishermen were asked for data
about their trip to obtain basic effort and catch data which we then compared to data from 1999 and
2007. Data included (appendix C):
- number of traps hauled during the trip: effort
- soaking time in days: how long the traps were in the water: effort
- fishing area (quadrant) (fig. 12)
- number of traps lost
- How many lobsters were caught: catch
- if they returned (discarded) any berried females: biological data
- if they returned (discarded) any undersized lobsters: biological data
- how much fish was caught (in lbs. later converted to kg): catch
Additional information for other research
- If they had seen whales or dolphins (not used in this thesis)
- If they discarded lionfish
Fig.11. Typical fishing boat (I. van Gerwen 2012)
18
3.2.3 Long interview
Long interviews were a combination of the short interviews and measuring sessions. First the short
interview was done to obtain basic CPUE data. Then the long measuring sessions were conducted to
obtain biological data to estimate length frequency, size at maturity, reproductive season, species
composition and sex ratio (table 2). Lobster was measured to the nearest mm carapace length, fish
was measured to the nearest cm fork length or total length. Approximately once a week the catch of
each boat was measured during a long interview. In the July-November 2012 a total 44 “long
interviews” were done (incl. 27 fish species composition, 31 lobster (length-frequency/sex/tar spot)
and 13 fish length-frequency data)
3.2.4 On board sampling trips
The biological data obtained with long interviews of the landed catch during port sampling was
expected to be skewed, because legislation prohibits the landing of P. argus with a carapace length
smaller than 95 mm, females that have eggs and individuals that are moulting (ecdysis). Therefore
nine on-board sampling trips were conducted in which the carapace length and sex of discarded
lobsters was determined. Also, females were examined for the presence of a tar spot and/or eggs,
and the merus length of discarded males was measured.
Before the start of the trip the fishermen were asked to divide the catch into discarded and landed
catch during the trip. Because of time constraints, most of the time only the discarded catch was
measured.
Fig. 12. Map of the Saba Bank divided in quadrats.
19
Because mixed fishes attributed a considerable part of the catch, species composition and length
frequency data was also obtained in all on-board sampling (except for one trip) trips and during port
sampling with long interviews.
Biological data collection
Lobster
3.2.5 Carapace length (CL)
The carapace length (CL) of P.argus was measured with a calliper in mm. The outside jaw of the
calliper is placed between the eyes and the inside jaw is placed where carapace ends and the tail
begins (fig. 13a+b).
3.2.6 Sex
The sex of the lobsters can be determined by the hind legs. The ends of the last hind legs of males
Fig. 13b Measuring the carapace length of a male P. argus with a caliper (I. van Gerwen
2012).
Fig. 13a Drawing of carapace length (CL) in detail
(CFR).
Fig. 14. Morphological difference between sexes in P. argus in last walking legs. Left = male (blue),
right = female (pink) (I. van Gerwen, 2012)
♂ ♀
20
are pointed (fig. 14). The ends of the legs of females have extra claws. Other sex specific features
include the presence of a tar spot and/or eggs for (adult) females and the length of the second leg in
(adult) males, which commonly longer than the rest of the legs.
3.2.7 Tar spot & Berried (females)
A tar spot is a sperm package placed by a male on the cephalothorax on the ventral side between the
walking legs of the female (fig. 15) and is an indicator of the maturity of the female. The tar spot is
scratched open to release the sperm and fertilize the eggs. Berried females are females carrying
eggs. To determine the presence of a tar spot and or eggs the female is examined from the ventral
side.
3.2.8 Merus length (males)
In the several crustacean species, i.e. Panulirus cygnus, allometric growth of the second walking leg
(pereiopod) of males has been found to be an indicator for their maturity (Evans et al., 1994;
Fig. 16. Measuring merus length of left walking leg of male P. argus with caliper (I. van Gerwen, 2012)
Fig. 15. Adult female with tar spot and eggs. (I. van Gerwen, 2012)
Tar spot
Eggs
21
Melville-Smith & de Lestang, 2006). Larger males typically have large pereiopods. We measured the
merus of the left side of the male with a calliper to the nearest mm. The calliper was placed behind
the pointed end of the merus and at the beginning of the merus where the isohium ends (fig. 16).
3.2.9 Size at maturity males
The males of P. argus were considered morphometrically mature based on changes in the
relationship between the length of the merus (ML) and the carapace length (CL) as determined by a
regression analysis (Melville-Smith & de Lestang, 2006). First, to test whether the merus length data
actually was allometric, two lines were fitted to the regression ML - CL. With a likelihood ratio test
the appropriateness of using two lines instead of one was tested. When this was determined each
data point was assigned either a 0 (immature) or a 1 (mature) based on their distance from one of
the lines. So if a point was closer to the left hand line then the point was assigned a 0, if it was closer
to the right hand line it was assigned a 1. The two lines were then refitted to these points, so the left
line to all the zeroes and the right line to the ones. Next, all the points were assigned a 0 or 1
according to their distance to either line. This process was iterated 100 times, but stabilized already
after 8 times .The lobsters were then allocated a maturity stage. To determine length when 50% of
the male P.argus is mature a logistic curve was fitted to the data.
3.2.10 Ecdysis
Ecdysis is the moulting of the exoskeleton of crustaceans in order to grow. Moulting animals have a
soft shell and when soft animals were observed they were documented.
Mixed Fish
3.2.11 Mixed fish species composition
Identification of the caught fish species was done based upon the reef fish identification book by
Humann & Deloach (2003). Either all fish species were counted or in some cases the lengths of the
whole catch was measured.
3.2.12 Fork length (FL) and Total Length (TL)
Depending on the fish species either the fork length (FL) was measured or the total length (TL) to the
nearest cm. The species with forked tails like H. melanurum (cottonwick) or Holocentrus rufus
(Longspine squirrelfish) FL was measured as opposed to species like Acanthostracion polygonia
(Honeycomb cowfish) and Chaetodon striatus (Banded butterflyfish) of which the TL was measured.
For the whole list see (appendix D).
22
3.3 Statistical analysis
3.3.1 Standardization of CPUE
Initially the CPUE was expressed as number of lobsters per trip, but because there was a difference in
trap hauls per trip this could influence the variation in CPUE separate from the abundance of
lobsters. The influence of trap hauls per trip could be taken into account by simply expressing the
CPUE as number of lobsters per trip per trap-haul. A simple regression graph where the number of
lobsters per trip was plotted against the number of traps showed a saturation effect of the number
of trap hauls on the number of lobsters being caught per trip (fig. 17). Simply put: the chance of
catching a certain number of lobster per trap-haul diminishes with increased trap-hauls per trip.
Therefore the trips were standardized to take out the “trap-haul” effect. The standardization of the
CPUE was used as described in of Tsehaye et al. (2007).
Other factors that could affect the CPUE, for example boat type or soaking time, were checked for
correlation with a descriptive regression analysis. In case of boat type there was no relation found
with catch per trip, and was therefore not used in the statistical analyses. There was no significant
relationship between soaking time and catch per trip and was not used in the analyses.
Standardisation involved the log-transformation of both the catch data and the effort data. Then the
regression coefficient β was calculated and the standardised CPUE was calculated with the following
formula:
(Tsehaye et al., 2007)
= standardized CPUE
= the mean value for in this case numbers of trap hauled per trip
= the number of traps hauled on trip
Catch data was available for the years 1999, 2000, 2007, 2011 and 2012. Because the data was
obtained in different months and to rule out the possibility of seasonal effects, a GLM was used on
y = 3.534x0.6436 R² = 0.1613
0
50
100
150
200
250
300
0 50 100 150 200 250
No
. Lo
bst
er
pe
r tr
ip
No. Trap-hauls
Fig. 17a +b. Power regression of catch per trip of 1999, 2007 and 2012 in the months July, August, September, October and November
against effort (no. trap hauls). (a) Catch: no. lobster per trip, (b) Catch: No. lobster per standardized trip.
y = 114.44x-0.162 R² = 0.0121
0
50
100
150
200
250
300
0 50 100 150 200 250
No
. Lo
bst
er
pe
r st
and
ard
ize
d
trip
No. Trap-hauls
23
data of the months July, August, September, October and November of the years 1999, 2007 and
2012. Those months were covered in both Dilrosun’s data and data of Toller & Lundvall 2008. Trips
are standardized on 75 trap-hauls per trip.
The calculated standardised CPUE values of the different years were analysed with a GLM with year
as a fixed factor. Since standardized CPUE-values were not normal distributed they were log-
transformed. Post hoc comparisons between years using a Bonferroni correction were performed.
3.3.2 CPUE weight per trip
The weight of male and female lobster was determined using the length weight relationship
determined by Dilrosun (2000). The following formulas were used:
Females: y = 3.3835x2.4724
Males: y =6.1318x2.2234
where x is the carapace length in cm and y the weight in grams. The total weight per trip was
calculated by summing up the individual weights of the lobsters. These estimated weights per trip
were then standardised in the same way as the CPUE no. lobster per trip per trap-haul. Trips were
standardized on 63 trap-hauls per trip.
3.3.3 Comparing of means
Means, standard errors and 95% BCa (Bias corrected and accelerated) confidence intervals were calculated with the use of bootstrapping. This non-parametric test was used to overcome large differences in sample size and the non-normal distribution of the data obtained during on board and port sampling. Bootstraps results came from 1000 bootstrap samples.
24
4. Results
4.1 Effort
During the sampling period 8 (partially) decked fishing boats were active on the Saba Bank. The crew
mainly consisted of the captain and one deckhand (sometimes 2). De boats were powered with
diesel engines; their horsepower ranging from 215 to 600hp (mean 406hp ± 41.7 S.E.). Vessel length
ranged from 30 to 39 ft. (9.14-11.89 m) with a mean of 34.4 ft. ± 1.12 S.E. (10.49m ± 0.34 S.E.). The
tonnage ranged from 5-15 tonnes with a mean of 8.6 tonnes. The fishermen owned a total of 1780
lobster traps, which they deployed on the Saba Bank and checked every 11.6 ± 0.38 S.E. days. These
traps were mainly of arrow head type but some fishermen also used square traps. The size of the
traps differed: 3-4 x 3-5 ft. (0.91-1.22m x 0.91-1.52m). Traps consisted of mesh steel wire, either
galvanized or coated. The size of the mesh in inch: 1x2, 1.5x1.5, 1.5x2, 2x2; in cm: 2.54x5.08,
3.81x3.81, 3.81x5.08, 5.08x5.08.
The fishing areas in 2012 for
lobster fisheries are mainly
situated in the North and East
parts of the Saba Bank (fig. 18).
The total number of trips doubled
from 1999 to 2007 but dropped
with 20% in 2012 based on the
months July-November (table 3).
Interestingly, the percentage of
trips that were lobster trips
decreased with more than 40%
over the time period of 13 years
(table 3). On the other hand the
average number of traps hauled
per trip in 2012 is similar to the
average of 2007. Both are
approximately 30 % more than the average in 1999 (table 3). The average number of trips per day
drops during the weekend in the months July –November in 2012 (appendix E). Due to storms (Isaac
21-28th of August and Raphael 13-16th of October), bad weather or maintenance, boats were out of
the water for several days, sometimes even longer.
Fig. 18. Lobster fishing activities in 2012 at the Saba Bank. Red= high, yellow=
medium, green=low fishing activity.
25
4.2 Catch
With the average weight per lobster in the months July-November and the average number of
lobsters per trip, the total landings of lobsters in kilo is calculated. Striking is that the total lobster
weight per year estimated in 2007 was 50% higher than the total catch in 1999. The total weight then
dropped again in 2012, even lower than 1999, due to decreased number of lobster per trip. The
mean weight per lobster (July-November) differed significantly between the years 1999, 2007 and
2012. Comparing the means with the use of bootstrapping an increase can be seen in weight per
landed lobster from 1999 (1,140.9g ± 482.6 SD, n=10420, BCa 95% CI [1132.11, 1149.42]) to 2007
(1,365g ± 547.9 SD, n=1203, BCa 95% CI [1333.75,1393.18]). The mean in weight per lobster in 2012
(1,217.9g ± 11.8 SD, n=1520, BCa 95% CI [1196.58,1240.54]) is significantly lower than 2007 but
higher than 1999.
Year Mean trip
day-1
SD
Estimated
Total no.
trips per
year
%
Lobster
trips
No. lobster
trips per year
(extrapolated)
Mean no.
traps hauled
per trip &
S.E.
Mean weight
per lobster (g)
& S.E.
Mean no.
Lobster per
trip & S.E.
Total
weight
(kg)
lobster
per year
July-
November
July -
November
July –
November
July-
November
1999 1.8 656 100 656 58.7±2.12 1,140.9±4.7 83.3±5.20 62,362
2007 3.7±2 1,310 76.2 998 80.1±2.78 1,365.4±15.8 69.6±3.72 94,888
2012 2.83±2.01 1,035 58.2 601 79.4±2.64 1,217.9±11.8 52.4±2.28 38,354
Table. 3 Data from short interviews and fishing trip log. Years 1999, 2007 and 2012 are covered.
26
4.3 Standardized CPUE
The regression coefficient of the number of traps in the GLM with the number of lobsters was β =
0.806 and 0.910 for the weight of the lobsters in kg. These values for β indicate an increase of the
catch per trip with the number of traps levelling off in the end. This confirms the saturation effect
mentioned in the materials & methods section. After log transformation of the standardized CPUE
the data was distributed normally. For both the CPUE in no. lobsters per trip and weight of catch per
trip the Levene’s test showed that the homogeneity of variances is equal between the three sampling
years (P>0.05). After standardizing the CPUE the ANOVA shows a significant effect of year on the
number of lobster per standardized trip (F (2, 330) = 36.21, p=<0.005). There was also a significant
effect of year on weight of catch per standardized trip (F (2, 118) = 9.801, p=<0.005). In figure 19 a
decrease can be seen for both standardized CPUE (numbers & weight) from 1999 to 2012. Also the
CPUE for no. lobsters differed significantly between years (p<0.005) in a pairwise test, which was not
the case for the weight per standardized trip where 2007 and 2012 did not differ significantly, as well
as 1999 and 2007. The average numbers of traps that were hauled were 58.7±2.12 SE, 80.1±2.78 SE
and 79.4±2.64 SE (July-November of 1999, 2007 and 2012 respectively).
Fig. 19. Trends in CPUE are expressed as: Mean of No. lobster per standardized trip and weight of total catch per standardized trip.
The total number of observations differed between years, for no. lobster the number of observations were; in 1999 n=80, in 2007
n=101, and in 2012 n=152. The number of observations for weight of catch were; in 1999 n=79, in 2007 n=13, and in 2012 n=26.
Error bars = 95% CI. Mean values of no of lobster per standardized trip a, b and c differ significantly as well as 1 and 2 for weight of
lobster per standardized trip.
0
10
20
30
40
50
60
70
80
90
100
0
10
20
30
40
50
60
70
80
90
100
1998 2000 2002 2004 2006 2008 2010 2012 2014
Cat
ch (
tota
l we
igh
t in
kg)
pe
r st
and
ard
ize
d t
rip
(C
I 95
%)
Cat
ch (
No
. lo
bst
er)
pe
r st
and
ard
ize
d t
rip
(C
I 9
5 %
)
Mean No. Lobsters perstandardized trip
Mean total weight of lobstersper standardized trip
a
b
c
1
1,2 2
27
4.4 Length - frequency
4.4.1 Landed
The mean length of landed lobsters in all years (1999-2000-2007-2011-2012) is at least 10mm above
the legal minimum size of 95 mm. Length-frequency distribution of landed lobsters do not show large
differences between the years 1999, 2007 and 2012 (fig. 21), but means differ significantly between
these three years; mean CL in 1999 106.1mm ± 18.5 SD 95% BCa CI [105.84, 106.32] (n=19478), 2007
111.8mm ± 18.4 SD 95% BCa CI [110.82, 112.76] (n=1518), 2012 107.6mm ± 16.5 SD 95% BCa CI
[106.71, 108.28] (n=1623). Striking is the relative low number of undersized lobster that was landed
in 2011 (4.8% of all the landed lobsters). The landing of undersized lobsters is not uncommon and
although there is a drop in 2011, the overall mean percentage of landed undersized lobsters is 18%
(table 4). Generally more male lobsters are landed than females, except for the year 2011. Length
frequency distribution of male and female lobsters can be found in figure 23. The mean carapace
length differed significantly in the landed catches between sexes; female 105.4 mm ± 16.6 SD 95%
BCa CI [104.03, 106.64] (n=653); male 109.0 mm ±16.3 SD 95% BCa CI [107.94, 110.13] (n=970).
4.4.2 Discarded versus landed catch
The mean length of lobsters differed significantly between landed and discarded catches in 2012. The
mean CL of discarded lobsters is 89.9 mm ± 20.9 SD 95% BCa CI [87.33, 92.34] (n=261) and landed
107.6 mm ± 16.5 SD 95% BCa CI [106.70, 108.44] (n= 1,623). The length- frequency distribution of the
landed and discarded lobsters can be seen in figure 20. In the discards length-frequency distribution
a clear drop is seen at 95 mm CL which is the size that is of which lobsters are allowed to be landed. A
trend can be seen in the discard of undersized lobsters per trip throughout the year. After the
summer months (June-August) the mean number declines then increases again after the winter
months (December-February). In both 2012 and 2013 the highest mean number of discarded
undersized lobsters is in the month of June (fig. 22). In contrast to the landed catches, more female
lobsters were present in the discarded catches; (74.7%).
Year Months Average
CL in mm
standard
deviation
(mm)
N
Undersized
% CL< 95
mm
Undersized
% CL< 90
mm
Female-
male ratio
(%)
1999 APR-NOV 106.1 18.5 19,478 32.3 19.7 39-61
2000 JAN-MAY 110.7 17.8 10,343 18.5 9.4 45- 55
2007 JUN-NOV 111.8 18.4 1,518 16.2 5.9 39-61
2011 OCT-DEC 118.3 15.9 461 4.8 1.1 58-42
2012 MAR-MAY
& JUL-NOV
107.6 16.5 1,623 20 5.7 40-60
Table 4. Length- frequency data of P.argus in landed catches over the years; 1999,2000,2007,2011 and 2012. Months the data is
collected; average carapace length and standard deviation; percentage of undersized lobster CL< 95 mm and CL<90mm; female-
male ratio in percentage.
28
Fig. 21. Length –frequency of landed lobster catches in the years 1999 (April-November), 2007 (June-November) and 2012 (March-
May & July-November)
0
5
10
15
20
25
Fre
qu
en
cy (
%)
Carapace length (mm)
1999, n=19478
2007, n=1518
2012, n=1623
Fig. 20. Length- frequency of P.argus in landed (black) n=1,623 and discarded (striped) n=256 in catches in 2012. Carapace length (CL) in mm and
frequency is number of individual lobsters.
0
5
10
15
20
25
30Fr
eq
ue
ncy
(%
)
Carapace length (mm)
discarded
landed
29
Fig. 23. Length- frequency of P. argus in 2012 for the different sexes n=1,623 in landed catches. CL is in mm and frequency in
number of lobsters (length classes 5mm).
0
50
100
150
200
250
<79 84 89 94 99 104 109 114 119 124 129 134 139 144 149 154 159 164 169 174 179 184 189
Fre
qu
en
cy (
#)
Carapace length (mm)
female
male
Fig. 22. Mean number of undersized lobster discarded per trip. Error bars are 95 %CI March 2012 – August 2013.
0
5
10
15
20
25
30
35
40
45M
ean
no
. un
de
rsiz
ed
lob
ste
rs p
er
trip
(B
Ca
95
% C
I)
30
4.5 Reproductive biology 4.5.1 Females
The mean number of berried female lobsters that was discarded per trip shows an irregular pattern
over months in 2012 and 2013 (fig. 24). In both years the highest mean of discarded berried females
per trip was found in March. Determining size at maturity for females is only possible during the peak
reproductive season, when mature females carry eggs. No peak in mean berried females is seen in
the months July-November. Therefore the analysis of size of maturity in females of data obtained in
the months July- November in 2012 is not accurate (appendix F).
4.5.2 Males
Two lines were fitted in a regression graph was and iterated 8 times until it converged (fig. 25). L50
was estimated at CL =92.2 mm S.E. 2.53 (fig. 25).
Fig. 25. Relationship between the merus length of the second pereiopod and carapace length of immature (black) and mature (red) male P.argus and
logistic regression fitted to the percentage of morphometrically mature males at different carapace lengths.
0
5
10
15
20
25
30
35
Me
an n
o. b
err
ied
fe
mal
es
pe
r tr
ip (
BC
a 9
5%
CI)
Fig 24. Mean number of berried females discarded per trip (error bars BCa 95% CI). March 2012 – August 2013.
31
4.6 Mixed fish
The mean number of landed fish was 50.0 with standard deviation of 51.0 (n=33 trips), the mean
number of discarded fish was 76.1 ± 92.5 SD (n=9 trips). In the discards 41 different species were
discarded as opposed to 49 species that were landed of the total of 57 species that were identified in
all the catches. Eight fish species were only found in discarded catches, especially Diodon
holocanthus, Holocanthus ciliaris and Pomacanthus arcuatus. The maximum number of species
identified in a single landed catch per trip was 22, with a mean of 10 species per catch. On the other
hand, the maximum number of species discarded in a single catch trip was 32 species, with a mean of
13.6 species. With the short interviews, a mean of 12.9 kg fish per landed catch (n=345) was
estimated, the calculation of the average weight per catch per trip of the length-frequency data
showed an average of 15.9 kg. Both estimates were lower than the 17.1 ± 15.5 SD kg per trip
estimated for 2007. The discarded catches contained, with a mean of 17.9 ± 21.2 SD (n=9) kg fish in
2012. More details about the fish species composition in the lobster traps can be found in Appendix
G.
4.6.1 Species composition
The fish species composition differed between landed and discarded catch. Landed fish mainly
consisted of species that were for own consumption (Balistes vetula, parrotfishes) or for commercial
purposes (groupers, grunts etc.) Some fish (Acanthuridae, Pomacanthidae, Ostraciidae etc.) are used
as food for the spiny lobsters in the holding pots. The grouper species (Serranidae) Epinephelus
guttatus (Red Hind) and Cephalopholis fulva (Coney) were almost completely landed as well as
Balistes vetula (Queen Triggerfish). Haemulon plumierii (White Grunt) and Haemulon melanurum
(Cottonwick) were present in high percentages in the landed catch (27% and 8% respectively) (fig.
26a), but were also well represented in the discarded catch (14% and 21%) (fig. 26b). Other fish that
were almost equally found in landings and discards belonged to the Acanthuridae (11.2% discards,
12.3% landed). The fish that belong to the Ostraciidae were more often discarded (23.9 %) than
landed (8.0 %).
Species composition in percentage of total weight sometimes differed from the species composition
in percentage of total number because of size differences between species. For instance, B. vetula
contributes 6% to the total number of landed fish, but 21% to the total weight of the landed catch.
Also the contribution of Ginglymostoma cirratum (Nurse Sharks) to the total weight is higher (9%)
than to the total number fish (1.2%) in the discarded catches. The opposite is seen for Chaetodon
striatus (Banded Butterflyfishes) that contributed more (6.5%) to the total number of fish than to the
total weight (1.7%).
4.6.2 Length-frequency
The length of all the fish in the landed catch is on average higher 26.4 cm ±7.06 SD, n=678 than in the
discarded catch 21.9 cm ±8.06 SD, n=609 (fig. 26e-f). Length-frequency graphs were made of fish
species that were present in both landed and discarded catch; Acanthostracion polygonia
(Honeycomb Cowfish, H. plumierii and H. melanurum. In some species a clear size division is seen
between landed and discarded catches similar to the length-frequency graphs of the total measured
fish. For example, the graph of Acanthostracion polygonia shows a separation between lengths of the
32
catches (fig. 27), in which the smaller individuals are part of discards (22.5 cm ± 2.82 SD, n=87, BCa
95 % CI [21.92, 23.07]) and the larger fishes are landed (25.0 cm ± 2.40 SD, n=50, BCa 95 % CI [24.31,
25.64]) their means differ significantly. On the other hand no clear difference in mean length was
seen in H.melanurum and H. plumierii between landed and discarded catches (Fig. 28 and 29). Still
the mean fork lengths of discarded H. plumierii (23.8 cm ± 2.35 SD, n=96, BCa 95 % CI [23.34, 24.30])
and H. melanurum (21.2 cm ± 2.17 SD, n=124, BCa 95 % CI [20.98, 21.61]) are also significant lower
than the landed fish of these species; H. plumierii: 25.1 cm± 2.24 SD, n= 216, BCa 95 % CI [24.78,
25.39], H. melanurum: 23.1 cm ± 2.45 SD, n=29, BCa 95 % CI [22.58, 24.12].
In the previous assessments the length frequency of the three fish species B. vetula, H.plumierii and
E. guttatus was measured. Compared to the data of 2007, mean length of B. vetula (fig. 30) does not
differ from the mean length 2011-2012, but in both periods significantly larger animals are landed
than in 1999-2000 (1999-2000= 31.7 cm ± 4.59 SD, n=267, BCa 95 % CI [31.18,32.26]; 2007=34.7cm ±
4.78 SD, n=134, BCa 95 % CI [33.95,35.43]; 2011-2012= 34.1cm ± 4.97 SD, n=54, BCa 95 % CI
[32.96,35.51]).
The mean fork length of landed H. plumierii increases significantly over the years (fig. 32) (1999-
2000=23.7cm ± 2.65 SD, n=719, BCa 95 % CI [23.51, 23.94]; 2007= 24.4cm ± 2.96 SD, n=713, BCa 95 %
CI [24.15,24.58]; 2011-2012= 25.1 ± 2.25 SD, n=210, BCa 95 % CI [24.77,25.41]).
Only the mean total lengths of landed E. guttatus (fig. 31) decreased significantly between the years
1999 and 2011-2012 (1999= 33.2cm ± 3.95 SD, n=260, BCa 95 % CI [32.70,33.67]; 2007=32.3cm ±
4.81 SD, n=166, BCa 95 % CI [31.60,32.98]; 2011-2012=31.3 ± 5.11 SD, n=133, BCa 95 % CI
[30.39,32.12]).
33
a. b.
Acanthostracion polygonia
14%
Acanthostracion quadricornis
6%
Acanthurus bahianus
6%
Acanthurus chirurgus
3%
Acanthurus coeruleus
3%
Cheatodon striatus
6%
Chilomycterus antillarum
4%
Haemulon melanurum
21%
Haemulon plumierii
14%
Lactophrys triqueter
3%
other fish 20%
discarded (#)
Acanthostracion polygonia
6%
Acanthurus bahianus
3%
Acanthurus chirurgus
6%
Acanthurus coeruleus
3%
Balistes vetula
6%
Cephalopholis fulva 3%
Epinephelus guttatus
11%
Haemulon melanurum
8%
Haemulon plumierii
27%
other fish 24%
Pseudopeneus maculatus
3%
landed (#)
Acanthostracion polygonia
6%
Acanthurus chirurgus
3%
Balistes vetula 21%
Calamus calamus
2%
Caranx crysos
4%
Cephalopholis fulva 2%
Epinephelus guttatus
15% Haemulon album
7%
Haemulon melanurum
2%
Haemulon plumierii
21%
other fish 17%
landed (weight)
Acanthostracion polygonia
15%
Acanthostracion quadricornis
4%
Acanthurus bahianus
2%
Cantherhines macrocerus
3%
Chilomycterus antillarum
5% Ginglymostoma cirratum
9%
Haemulon melanurum
18%
Haemulon plumierii
16%
Lactophrys triqueter
2%
other fish 24%
Pomacanthus paru 2%
discarded (weight)
0
5
10
15
20
25
30
3 6 9
12
15
18
21
24
27
30
33
36
39
42
>4
2
Fre
qu
en
cy (
%)
FL (cm)
landed
Fig 26(a-f). Pie diagrams a-d depict species compositions in percentages of total nonzero catches. A & b are based on total number of fish
caught, c & d are based on the total weight (kg) of catch. Graphs e & f show length-frequency of total fish in percentages. Graphs a-e are
based on landed catches of 33 trip, c on 17 trips sand b-d-f are based on discarded catches of 9 trips.
e. f.
d. c.
0
5
10
15
20
25
30
3 6 9
12
15
18
21
24
27
30
33
36
39
42
>4
2
Fre
qu
en
cy (
%)
FL (cm)
discarded
34
Fig. 27. Length- frequency of .A polygonia. Frequency is number of fish and length is TL in cm. Catches are divided in landed fish
(black) and discarded fish (striped).
0
5
10
15
20
25
14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Fre
qu
en
cy (
%)
TL (cm)
A. polygonia
landed
discarded
0
5
10
15
20
25
30
35
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Fre
qu
en
cy (
%)
FL (cm)
H. melanurum
landed
discarded
Fig. 28. Length- frequency of H. melanurum. Frequency is number of fish and length is FL in cm. Catches are divided in landed fish
(black) and discarded fish (striped).
0
5
10
15
20
25
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Fre
qu
en
cy (
%)
FL (cm)
H. plumierii
landed
discarded
Fig.29. Length- frequency of H.plumierii (2012). Frequency is number of fish and length is FL in cm. Catches are divided in landed fish
(black) and discarded fish (striped).
35
0
5
10
15
20
25
30
21 24 27 30 33 36 39 42 45 48
Fre
qu
en
cy (
%)
FL (cm)
B. vetula
1999-2000, n=267
2007, n=134
2011-2012, n=54
Fig.30. Length- frequency of B. vetula in the periods 1999-2000, 2007 and 2011-2012 of the landed catch. Frequency is percentage of
total caught fish and length is FL in cm.
Fig.31. Length- frequency of E. guttatus in the periods 1999, 2007 and 2011-2012 of the landed catch. Frequency is percentage of
total caught fish and length is TL in cm.
0
5
10
15
20
25
30
21 24 27 30 33 36 39 42 45 48
Fre
qu
en
cy (
%)
TL (cm)
E. gutattus
1999, n=260
2007, n=166
2011-2012, n=133
36
Fig. 32. Length- frequency of H.plumierii in the periods 1999-2000, 2007 and 2011-2012 of landed catch. Frequency is percentage of
total caught fish and length is FL in cm.
0
5
10
15
20
25
30
35
14 16 18 20 22 24 26 28 30 32 34 36 38 40
Fre
qu
en
cy (
%)
TL (cm)
H. plumierii
1999-2000, n=719
2007, n=713
2011-2012, n=210
37
5. Discussion
5.1 Lobster
5.1.1 Catch, effort and CPUE
The striking decrease in annual catch between 2007 and 2012 is in line with the observations of the
annual total lobster catch in Caribbean (CRFM, 2011; FAO, 2013). The decline in annual catch of spiny
lobster on the Saba Bank can be partially be explained by the observed decline in fishing effort.
Fishing effort, expressed as the number of trips per year, has declined on the months July-November
of 1999, 2007 and 2012. Also, the total number of traps used for fishing has declined as well, from
approximately 2,800 lobster traps in 2000, to 2,200 in 2007 and 1,780 lobster traps in 2012.
Remarkably, a shift is seen in target species, in 1999 almost 100% of all fishing trips targeted lobsters.
In 2007 this was already 76% and in 2012 it dropped to 58% of the fishing trips. Thus fishing effort is
shifting more towards “red fish” trap fisheries (Toller & Lundvall, 2008). The reason for this change is
not clear; in other fisheries the choice to shift in target species is attributed to change in market,
revenue, and the decline of target species (Bucaram & Hearn, 2014). In Belize, for example, despite
declining spiny lobster stocks an increase in effort has been documented (Gongora, 2010).
The estimate of annual fishing effort could be an under-estimate, because sampling was done in July-
November which is in the hurricane season. In 2012 several storms passed Saba during these months,
forcing the fishermen to take their boats out of the water. Therefore fewer fishing trips were
undertaken and logged. Extrapolating the mean number of trips per day of these months to estimate
the total trips per year, can therefore result in a lower number of trips than were undertaken in
reality. This can be illustrated with data of Dilrosun (2000). He has logged all the lobster trips
throughout the year from May 1999 to May 2000. In the months July-November 275 trips were
logged. This accounts for an average of 1.8 trips per day, in those months. When extrapolated, this
results in 656 trips for the year 1999. The actual number of lobster trips (May 1999-April 2000) was
731. This means that by extrapolating, we potentially underestimated the total annual number of
trips with 10%. This underestimation influences also the total weight of lobster per year.
The standardized catch per unit effort decreased significantly between the years 1999 - 2012 which is
a strong indication that the abundance of spiny lobsters is declining on the Saba Bank. In 1999 a
mean of 81.9 ± 1.07 S.E. no. of lobsters per standardized trip was caught declining to 60.5 ± 1.06 S.E.
in 2007 and 44.4 ± 1.05 S.E. in 2012. Although the standardized CPUE (in weight per trip) did not
differ significantly between the years 2007 and 2012, the overall trend is that of a declining CPUE,
both in numbers of lobster per trip and weight of catch per trip. These trend in declining of CPUE is
also seen in lobster fisheries in Belize (Gongora, 2010).
Very few similar studies, like this thesis, have been performed on Caribbean spiny lobster populations
throughout the Caribbean (CRFM, 2011). Especially, long-term monitoring datasets on P. argus
fisheries are rare. Still, with the scarce information available, almost all lobster populations
throughout the Caribbean have been said to be either fully or over exploited (CRFM, 2011, appendix
A). Therefore management plans and fishermen mainly focus in reducing effort. Whether the
declining trend in CPUE of lobsters caught on the Saba Bank is caused by the local fishery is not clear.
Other factors, like habitat degradation (Kough et al., 2013; Maxwell et al. 2010), have been said to
cause the decline of P. argus stocks in the Caribbean.
38
One of the factors influencing local P. argus abundance is the connectivity between different
Caribbean spiny lobster stocks (Kough et al. 2013; Silberman et al., 1994). Due to their long larval
state models of Butler et al. (2013) suggest that fisheries from, for example Venezuela and Dominican
Republic, influence the recruitment and thus abundance of P. argus on the Saba Bank. If animals are
caught before they are sexually mature, and have not been able to reproduce, then no larvae will be
taken with the currents and will recruit other areas like the Saba Bank. On the other hand this does
not imply that the P. argus population on the Saba Bank is only dependent on foreign fishery activity
and management. Models (Butler et al., 2011; Butler et al., 2013) show that a large part of the larvae
recruit areas within 400 km of the spawning area. This means that P. argus population at the Saba
Bank is influenced by this “self-recruitment”. Thus to fully understand the lobster fisheries and
changes in catch and effort it is important to incorporate and understand the spatial level of larval
distribution throughout the Caribbean (Kough et al, 2013).
It was difficult to quantify if there was a change in fishing area because of the different methods to
determine fishing area used in previous assessments (Dilrosun, 2000; Toller & Lundvall, 2008). The
quadrants we used differed in size and location from previous assessments. Nonetheless, by visually
comparing the maps of previous assessments with each other, the fishing areas do not seem to have
changed greatly. Only a part of the Saba Bank is fished, due to two reasons. The first is the cost of
fuel. With increasing fuel costs it is not likely that fishing areas will expand further from Saba (Pauly,
2009). This increase in fuel cost might also be the cause of the decrease in fishing effort (total trips
per year) from 1999 to 2012 because the catch is less profitable.
The second reason is that P. argus dwells in shallow waters (Holthuis, 1991) and the shallowest part
with suitable habitat of the Saba Bank is the nearest to the Island of Saba. However, although the
fishing areas have not greatly changed in the past, this does not mean that traps are always dropped
at the same place. Every trip the traps that are hauled are moved a couple of meters (personal
observations). Sometimes all the traps are taken to a new area that has not been fished for a while.
An interesting observation was that when a lobster was caught in a trap there were almost always
more lobsters in the same trap (personal observations). This phenomenon can be explained by the
social behaviour of the lobsters. Adult spiny lobsters tend to aggregate (Lavalli & Herrnkind, 2009).
This mechanism is used in trap fisheries by fishermen were they retain small or undersized lobster in
the traps to attract other, preferably larger lobsters.
5.1.2 Length-frequency
The mean CL of the landed lobsters in 2012 (107.5mm ± 16.5 SD n=1623) on the Saba Bank is large
compared to lobsters caught in the, intensively fished, Florida Keys where lobsters above the size
class 110-119 mm are rarely caught (Maxwell et al., 2010). In the no-take Marine Reserve the Dry
Tortugas larger lobsters are caught. Also, the mean carapace length of landed lobsters from the Saba
Bank is considerably higher than the mean CL of spiny lobsters that are caught in Belize (male:
83.8mm, female: 79.9mm; Gongora, 2010). This difference in mean carapace length can be attributed
by the difference in fishing techniques, lower size limits, but also the status of the local P.argus
population in Belize.
Compared to the size limits for catching P.argus set throughout the Caribbean (minimum catch size
82.55mm, 72.6mm and 95mm CL (CRFM, 2011, appendix A)), the mean CL of the lobsters caught on
39
the Saba Bank suggests that mainly adults are caught that are sexually mature, and that there is thus
an healthy reproductive population on the Saba Bank.
A relative high percentage (20%) of the landed catch in 2012 consisted of undersized lobsters.
However, the percentage of the landed lobsters that are smaller than 90 mm CL is much lower (5.7%)
This is probably because most fishermen estimate the size of the lobster visually (personal
observations). So therefore there could be a measuring error of a few mm. This error is simply
overcome by the use of lobster gauges or callipers. Also, looking at the trend in average number of
undersized lobsters that were discarded in the months July-November, it seems that there is a peak
in the summer. It can be hypothesized that when more undersized lobsters are caught it is more
likely that a higher number will be landed. The mean CL should therefore drop during the summer
months. This can explain the difference in average CL in April-November 1999 (106.1mm ± 18.5 SD)
and mean CL in January-May 2000 (110.7 ± 17.8 SD) (Dilrosun, 2000). The trend seen in number of
undersized lobsters caught and discarded throughout the years 2012 and 2013 can be caused by
changes in water temperature due to seasonality. Juvenile and adult lobsters are known for their
change in mobility depending on sea water temperature (Herrnkind, 1980).
On average more male than female spiny lobsters are landed. Females are discarded more often
because it is not allowed to land females either carrying eggs. Also females are often smaller than
males (George, 2005) and are therefore more likely to be discarded.
5.1.3 Reproductive biology
Berried females were caught throughout the year, but a peak was seen in the spring especially in
March. This finding is consistent with the assessment of Dilrosun (2000), where he also found a peak
in the number of berried females in March on the Saba Bank. In Cuba (Cruz & Leon 1991), Mexico
(Cruz et al., 2001), Florida (Bertelsen & Matthews 2001), and several other areas in the Caribbean
(Ayra & Cruz, 2010) reproduction was highest from March-May. Therefore, if there is a spawning
season of P. argus at the Saba Bank it would be likely to occur in the spring (March-May). However,
spawning of P. argus occurs throughout the year on the Saba Bank, which is common for areas closer
to the equator (Butler et al., 2009). This is probably due to the minimal seasonal temperature
changes as opposed to Florida where a clear spawning period was found in spring (Bertelsen &
Matthews, 2001; Butler et al., 2009).
Calculating size at maturity for females was not possible because the percentage of females that
were sexually mature and had a tar spot was too low. To estimate size at maturity of females I would
recommend repeating the measurements again in March. I expect that the percentage of sexually
mature females with a tar spot to be higher.
The size at maturity for males of 92.2 mm carapace length is just below the size limit of 95 mm.
Therefore, the minimum size can be considered an accurate legislative measure. However, the
importance of large males is overlooked. Large males have the ability to fertilize the eggs of both
small and large females as opposed to smaller males that can only fertilize the whole clutches of
small females (MacDiarmid & Butler 1999). Thus if only small male lobsters remain the full spawning
potential of large females can’t be reached. If the size at maturity of spiny lobsters on the Saba Bank
is representative for the rest of the Caribbean P. argus population, size limits of 82.55mm (i.e.
40
Bahama’s; Turks & Caicos) or 76.2 mm (i.e. Belize) (CRFM, 2011) would probably miss the objective of
ensuring that captured lobsters have had the chance to reproduce.
Although management plans throughout the Caribbean already in place but still little is known about,
fecundity, size at maturity, reproductive season etc. (Ayra & Cruz, 2010). No recent articles are
published on these subjects. I have found only one article published which described a similar
analysis on P. argus to determine the size at maturity of male lobsters (Evans et al. 1995). I would
therefore recommend the investigation of biological parameters i.e. size at maturity throughout the
Caribbean as reference points and to validate management measures.
5.2 Mixed Fish
It is suggested that fisheries on the spiny lobsters can have negative effects on the fish biodiversity
and biomass distribution on the Saba Bank (Toller et al. 2010). Lobster traps catch a variety of reef
fishes in addition to lobsters. In this study it has been found that approximately 20% of the known
fish species on the Saba Bank are caught by the lobster traps. Whether this has a significant effect on
the fish assemblage is discussed below.
Approximately 7800 - 9800 kilo mixed fish caught on the Saba Bank is landed annually. The projected
annual mixed fish landing in 2012 is half of the amount that Toller and Lundvall (2008) estimated in
2008. This can be explained by the decrease in the total fishing trips per year between 2007 and
2012. As for the lobsters, the estimation of the annual mixed fish landing in 2012 could be low
because of the less fishing trips per day in the months July- November compared to the rest of the
year. In addition to the landings a similar amount of mixed fish is discarded. The variation within the
discarded catches was high. There were also many fish species that where both landed and
discarded.
There are several explanations of some fish species being present in both landed and discarded
catches. One reason is size: some small fish are not saleable and are discarded in the hope that they
grow and are caught another time (i.e. H. melanurum conversation fishermen). Another reason is
that there is no demand for those fish at that time (H.melanurum & H. plumierii). Some fishermen
use some species of fish as food for the lobsters in the holding pots (Toller & Lundvall, 2008). Also
some fish species, i.e. Blue tangs or surgeon fishes, that are not marketable, but are normally used
as lobster food are sometimes not taken out of the traps because they have spines and it takes too
long to remove them from the traps (personal observations).
Little research has been done on the by catch of lobster traps in the Caribbean. However, Hawkins et
al. (2007) did look at the effect of trap fishing reef fish communities in the Caribbean. Although they
did not mention the traps being used for lobster fishing, the traps appear similar to the lobster traps
used by the Saban fishermen with the exception of the shape of the funnel entrance. Also similar fish
species were caught with these traps (Hawkins et al. 2007) as with the lobster traps on the Saba
Bank. Hawkins et al. (2007) found that trap fishing on high intensities “…cause serious over-fishing,
reduce biodiversity and alter ecosystem structure”. Although it is difficult to determine the effects of
the lobster trap on the reef fish species on the Saba Bank, the article of Hawkins et al. (2007) makes it
clear that it is important to understand the effects of lobster trap fisheries on the Saba Bank.
41
Only one species (Balistes vetula) that is caught in the lobster traps is listed on the IUCN red list of
endangered species as vulnerable (appendix G). However, the IUCN red list statuses of many of the
fish species that are caught in the lobster traps have not been evaluated yet. Also, if the IUCN list
values a species as “Least Concern” it does not mean that local populations are not threatened.
Therefore, the estimation of effects of lobster traps on reef fish populations has to be done with
caution. Balistes vetula is a species that is both of commercial value for the fishermen, but also is
known to be a P. argus predator (Lavalli & Herrnkind, 2009), which could be the reason they are
always landed when caught. High bodied species that are commonly found in catches like the
butterflyfishes, angelfishes, acanthurids and triggerfishes and which usually have little economic
value are known to benefit from vertical gaps in the traps (Johnson 2010). So they can escape and
unwanted bycatch is prevented.
The lionfish, Pterions volitans is an invasive species from the Indo-Pacific region. It has spread
throughout the Caribbean and has now also populated the Saba Bank. This species is known for its
rapid reproduction rate and because it has venomous spines it has little to no known natural enemies
(Côté et al., 2013), it therefore is important to monitor their presence in the catches because they
could have effects on the banks biodiversity. Compared to data from the red fish fisheries data
(0.65±1.2 SD no. lionfish/trap n=101) (Boonstra, 2013) the catch rate of P. volitans of lobster traps is
low (0.03±0.1 SD no. Lionfish/trap n=158). Because redfish traps are deployed in deeper waters it is
likely that this species has only populated the more deeper areas, perhaps because food is more
available or they are less prone to be predated upon in greater depths.
42
Conclusions The CPUE of spiny lobster has decreased significantly over the course of 13 years,
indicating a decrease in abundance. In 1999 a mean of 81.9 ± 1.07 S.E. no. of lobsters
per standardized trip; 60.5 ± 1.06 S.E. in 2007; 44.4 ± 1.05 S.E. in 2012. Weight of
catch per standardized trip did not differ significantly between the years 1999-2007
and 2007-2012
No apparent changes in fishing areas were observed between 1999 and 2012.
A potential underestimation of 10% of the total annual catch for both lobster and
mixed fish by extrapolating catches of July-November
The number of fishing trips increased between 1999 and 2007 but dropped again in
2012. Fishing trips decreased by 30% between 2007 to 2012.
Spawning of P. argus occurs throughout year, with a peak in March-June.
The mean carapace length of P. argus in landed catches is higher than the size at 50%
maturity estimated for male lobsters (92 ±2.5 SE mm CL) on the Saba Bank.
The mean length of landed male and female lobster suggests that only large, mature
specimens are landed.
Catches of landed mixed fish total in approximately 9800kg annually. It is estimated
that the same amount is discarded. Approximately 20% of known fish species on the
Saba Bank are caught with lobster traps.
43
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50
Appendix A
Country Resource Status Management Objectives Current Regulations
Anguilla Fully exploited
Minimum size limits (carapace
length > 95 mm or 7.05oz)
Prohibition on taking berried or tar-
spotted females
Prohibition on taking moulting
individuals
Prohibition on taking lobsters by
spear gun, harpoon or hook of any
description
Antigua & Barbuda
Fully exploited
Sustainable at
current levels of
fishing
Rebuilding stocks in depleted areas
Minimum size limits (carapace
length ≥ 95 mm)
Prohibition on taking berried or
moulting individuals
Prohibition on removal of eggs
from a spiny lobster
Gear restrictions
Prohibition on taking lobsters by
any method other than hand, loop,
pot or trap
Bahamas
Unknown (large
degree of
uncertainty)
Recent declines in
landings
Fisheries
Department
considers stocks in
fairly good
condition
Minimum size limits (carapace
length >82.55 mm and tail length
>139.7 mm)
Prohibition on capture, possession
or sale of berried individuals
Closed season (1 April – 31st July)
Ban on possession of lobster with
swimmerettes removed
Prohibition on removal of eggs
from a spiny lobster
Vessels operating with a
sportfishing permit are allowed
only 10 lobster onboard at any time
Barbados
Unknown
Anecdotal evidence
suggests increase in
abundance
To promote the sustainable harvest
of lobster for domestic use and the
local tourism market in order to
achieve the maximum economic
return from the resource over the
long run
Prohibition on harvest of berried
individuals or removal of eggs
Closed season
Marine Protected Areas
Belize
Overexploited
Threatened by
increase in effort,
inadequate
management,
alteration to habitat
and lack of research
Ensure catch does not exceed
sustainable levels
Discourage destructive fishing
practices
Improve management through
national and international
collaborations
Minimum size limits (carapace
length >3 in. and tail weight >4 oz.)
Prohibition on taking berried or
moulting individuals
Closed season (15th Feb – 14th June)
Ban on landing dead lobsters
Prohibitions on use of SCUBA,
hookah, spearguns and explosives
No fishing in marine reserves or on
the forereef
Table 5: Summary of status, management objectives and current regulations for P. argus fisheries in CARICOM countries. (CRFM, 2011)
51
Country Resource Status Management Objectives Current Regulations
Dominica
Populations of the
south and west
coasts have
declined in
abundance and size
Stocks off northeast
coast considered in
better shape
Rebuild stocks in depleted areas
Minimum size limits (not outlined)
Prohibition on taking berried or
moulting individuals
Closed season (not outlined)
Ban on landing dead lobsters
Prohibitions on use of SCUBA,
spearguns and loops
*Note: Regulations are not currently in
force but used as a matter of policy
Grenada
Overexploited in
nearshore areas
Increasing scarcity
in traditional fishing
areas
Promote sustainable harvest for
local (tourism market) use and
export in order to achieve long
term economic benefits
Rebuild stocks in depleted areas
Minimum size limits
Gear restrictions
Prohibition on taking berried or
moulting individuals
Closed season
Ban on landing dead lobsters
Guyana Guyana does not have a management plan for lobster
Haiti Overexploited
Rehabilitation of degraded habitats
Training of fishermen in basic
literacy and more advanced topics
such as fisheries assessment and
management
Fish stock assessments
Fisher registration
Closed season (April 1 – September
30)
Jamaica Overexploited
Restore/rehabilitate fishery
Control and monitor processing
activities
Optimize foreign exchange earnings
Protect and enhance lobster
habitat
Minimum size limits
Prohibition on taking berried
individuals
End of season declaration of lobster
by processors
Closed season (April 1 – June 30)
Gear restrictions (industrial fishery
only)
No fishing in marine reserves
Montserrat
Lobster populations
off west coast have
declined in size and
abundance
Lobsters off east
coast in relatively
better shape
Rebuild stocks in depleted areas
(particularly off west coast) None
St. Kitts & Nevis
Overexploited in
nearshore areas
Increasing scarcity
in traditional fishing
areas
Rebuild stocks in depleted areas
Minimum size limits
Restrictions on fishing gear
Prohibition on taking berried or
moulting individuals
Closed season
Ban on taking lobsters that are not
whole
Prohibition on use of speargun and
SCUBA
Requirement for marking of traps
St. Lucia
Overexploited in
nearshore areas
Increasing scarcity
in traditional fishing
areas
Sustainable exploitation of stocks
Minimum size limits
Gear restrictions
Prohibition on taking berried or
moulting individuals
Closed season
Prohibition on use of spearguns
and SCUBA
Requirement for marking of traps
52
Country Resource Status Management Objectives Current Regulations
Limited entry for pot fishers
St. Vincent & the
Grenadines Overexploited in
nearshore areas
Rebuild stocks in depleted areas
Sustainable management of the
resource
Minimum size limits
Gear restrictions
Prohibition on taking berried or
moulting individuals
Closed season (May through
August)
Suriname Suriname does not have a management plan for lobster
Trinidad & Tobago Trinidad & Tobago does not have a management plan for lobster
Turks & Caicos Fully
exploited/stable
Reduce fishing effort
Stabilize fluctuations in the fishery
Improve control over size at 1st
capture
To increase revenues
Reduce catches made during the
closed season
Minimum size limits (CL>82.55 mm;
tail>5 oz)
Prohibition on taking berried
individuals
Closed season (April 1st – June 30th)
Ban on SCUBA/hookah diving
Licensing for all fishers, vessels and
processing plants
53
Country
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Anguilla No closed season
Antigua & Barbuda No closed season
Bahamas
Barbados
Belize
Dominica No closed season
Grenada
Guyana No lobster fishery
Haiti
Jamaica
Montserrat No closed season
St. Kitts & Nevis No closed season
Saint Lucia
St. Vincent & the
Grenadines
Suriname No lobster fishery
Trinidad & Tobago No lobster fishery
Turks & Caicos
Appendix a: Seasonal closures for P. argus in CARICOM countries (CRFM, 2011)
54
SABA BANK FISHERIES RESEARCH LOGBOOK
Date:
Boat:
Lobster Pot
Redfish Pot
Longline
No. of Traps: No. of Traps: No. Hooks on Line:
Soak Time: days Soak Time: No. Lines pulled:
Fishing Depth: Fishing Depth: Fishing Depth:
GPS: N 17° GPS: N 17° GPS: N 17°
W 63°
W 63°
W 63°
Quadrat: Quadrat: Quadrat:
Lost traps No Lost traps No
Mixed Fish: Lbs Redfish: Lbs Redfish: Lbs
Lobster: No Mixed Fish: Lbs Mixed fish: Lbs
Berried: No Lobster: No
Shorts: No
Lionfish No Lionfish No Lionfish No
Pelagic Trolling Species
No./Lbs
No. Lines:
Duration (hr):
FAD:
GPS: N 17°
W 63°
Quadrat:
Whales Species Time
Group size Position
Appendix C
55
Fish species FL/TL Fish species FL/TL Fish species FL/TL Fish species FL/TL
Chaetodontidae Haemulidae Priacanthidae Mullidae
Cheatodon striatus TL Haemulon flavolineatum FL Priacanthus arenatus FL Pseudopeneus maculatus FL
Cheatodon capistratus TL Haemulon plumierii FL Aulostomidae Mulloidichthys martinicus FL
Cheatodon ocellatus TL Haemulon carbonarium FL Aulostomus maculatus TL Ginglymostoma cirratum TL
Pomacanthidae Haemulon aurolineatum FL Diodontidae Bothidae
Holacanthus ciliaris TL Haemulon melanurum FL Chilomycterus antillarum TL Bothus lunatus TL
Pomacanthus paru TL Haemulon album FL Chilomycterus antennatus TL Scorpaenidae
Pomacanthus arcuatus TL Lutjanidae
Diodon holocanthus TL Pterois volitans TL
Holacanthus tricolor TL Lutjanus jocu FL Ostraciidae
Acanthuridae Lutjanus apodus FL Acanthostracion polygonia TL
Acanthurus coeruleus TL Lutjanus synagris FL Acanthostracion quadricornis TL
Acanthurus bahianus TL Ocyurus chrysurus FL Lactophrys trigonus TL
Acanthurus chirurgus TL Lutjanus buccanella FL Lactophrys triqueter TL
Carangidae
Rhomboplites aurorubens FL Lactophrys bicaudalis TL
Caranx ruber FL Lutjanus vivanus FL Balistidae
Caranx crysos FL Serranidae
Balistes vetula FL
Sparidae
Epinephelus morio TL Monacanthidae
Calamus calamus FL Mycteroperca venenosa TL Canthidermis sufflamen TL
Scaridae
Epinephelus guttatus TL Aluterus scriptus TL
Sparisoma viride FL Cephalopholis fulva TL Cantherhines pullus TL
Scarus taeniopterus FL Holocentridae Aluterus schoepfi TL
Sparisoma aurofrenatum FL Holocentrus adscensionis FL Cantherhines macrocerus TL
Sparisoma chrysopterum FL Holocentrus rufus FL
Appendix D
56
Appendix E
0
1
2
3
4
5
6
Monday Tuesday Wednesday Thursday Friday Saturday Sunday
No
. Tri
ps
57
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 20 40 60 80 100 120 140 160 180
Frac
tio
n m
atu
re
Carapace length (mm)
Appendix F
58
Land
ed (#)
Discard
ed
(#)
%
of
total
p
Me
an
(#)
Me
an
(#)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
(#)
Me
an
(#) no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
Ch
aeto
do
ntid
ae
Ch
eato
do
n stria
tus
0.7
0
.12
0
.3
2.8
0
.8
4
2.2
2
.1
6.5
0
.67
4
.9
7.3
1
.5
6
4.0
2
.5
Ch
eato
do
n ca
pistra
tus
0.0
0
.00
0
0.3
0
.11
0
.2
2.0
1
2.0
Ch
eato
do
n o
cellatu
s 0
.0
0.0
0
0
0
.1
0.1
1
0.1
1
.0
1
1
.0
P
om
acanth
idae
H
ola
can
thu
s ciliaris
0.0
0
.00
0
0.7
0
.44
0
.6
1.3
0
.4
4
1.2
1
.4
Po
ma
can
thu
s pa
ru
0.5
0
.15
0
.3
1.8
0
.7
5
1.5
1
.7
0.4
0
.22
0
.3
1.5
0
.5
2
1.4
2
.0
Po
ma
can
thu
s arcu
atu
s 0
.1
0.0
3
0.0
1
.0
1
1
.0
0
.3
0.1
1
0.2
2
.0
1
2
.0
H
ola
can
thu
s tricolo
r 0
.2
0.1
2
0.1
1
.0
0.0
4
1
.0
1.0
1
.9
0.4
4
1.4
3
.3
0.9
4
2
.3
2.7
Acan
thu
ridae
A
can
thu
rus co
eruleu
s 3
.2
0.6
1
1.6
2
.7
0.8
2
0
2.1
1
.3
2.9
0
.56
2
.2
4.0
0
.7
5
3.1
2
.1
Aca
nth
uru
s ba
hia
nu
s 3
.2
0.3
3
1.6
4
.8
0.9
1
1
3.5
1
.7
5.6
0
.56
4
.2
7.6
1
.1
5
3.8
3
.5
Aca
nth
uru
s chiru
rgu
s 5
.9
0.4
8
2.9
6
.1
1.1
1
6
3.4
1
.8
2.7
0
.78
2
.0
2.6
0
.8
7
2.0
1
.8
Caran
gidae
C
ara
nx ru
ber
0.1
0
.03
0
.0
1.0
1
1.0
0.6
0
.22
0
.4
2.0
0
.7
2
1.7
3
.0
Ca
ran
x crysos
1.8
0
.03
0
.9
29
.0
1
2
9.0
0.0
0
.00
0
Sparid
ae
Ca
lam
us ca
lam
us
2.2
0
.30
1
.1
3.7
0
.8
10
2
.7
1.8
0
.3
0.1
1
0.2
2
.0
1
2
.0
Scarid
ae
Spa
risom
a virid
e 0
.1
0.0
6
0.1
1
.0
0.0
2
1
.0
1.0
0
.1
0.1
1
0.1
1
.0
1
1
.0
Sca
rus ta
enio
pteru
s 2
.5
0.3
0
1.2
4
.1
0.9
1
0
3.0
1
.7
0.4
0
.22
0
.3
1.5
0
.5
2
1.4
2
.0
Spa
risom
a a
uro
frena
tum
1
.0
0.3
0
0.5
1
.6
0.5
1
0
1.4
1
.4
0.9
0
.44
0
.7
1.5
0
.4
4
1.4
1
.5
Spa
risom
a ch
rysop
terum
1
.5
0.4
2
0.7
1
.7
0.6
1
4
1.5
1
.3
0.3
0
.11
0
.2
2.0
1
2.0
Ap
pe
nd
ix G.Fish
species co
mp
ositio
n o
f land
ed (3
3 trip
s) and
discard
ed (9
trips) catch
es w
ith d
escriptive statistics fo
r each sp
ecies taken
from
no
n-zero
catches b
ased o
n co
un
ts.
Co
lors o
n sp
ecie
s nam
e dep
ict status o
n th
e IUC
N red
list. Gre
en= Least co
ncern
, Grey= n
ot evalu
ated, B
lue= N
ear Threaten
ed, P
urp
le=V
uln
erable, yello
w=n
o d
ata
59
Lan
ded
(#)
D
iscarde
d (#)
%
of
total
p
Me
an
(#)
Me
an
(#)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
(#)
Me
an
(#) no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
Hae
mu
lidae
H
aem
ulo
n fla
volin
eatu
m
0.1
0
.03
0
.0
1.0
1
1.0
0.0
0
.00
0
Ha
emu
lon
plu
mierii
28
.4
0.9
7
14
.2
14
.6
0.9
3
2
9.4
1
.5
14
.6
0.3
3
11
.0
33
.0
1.7
3
5
.8
17
.1
Ha
emu
lon
carb
on
ariu
m
0.1
0
.03
0
.0
1.0
1
1.0
1.3
0
.11
1
.0
9.0
1
9.0
Ha
emu
lon
au
rolin
eatu
m
0.1
0
.03
0
.1
2.0
1
2.0
0.0
0
.00
0
Ha
emu
lon
mela
nu
rum
8
.7
0.4
8
4.4
9
.0
2.2
1
6
3.6
1
.8
20
.9
0.4
4
15
.8
35
.5
1.5
4
1
1.5
7
.2
Ha
emu
lon
alb
um
0
.8
0.1
5
0.4
2
.8
0.7
5
2
.4
1.8
0
.1
0.1
1
0.1
1
.0
1
1
.0
Lu
tjanid
ae
Lutja
nu
s jocu
0
.1
0.0
3
0.0
1
.0
1
1
.0
0
.0
0.0
0
0
Lu
tjan
us a
po
du
s 0
.1
0.0
3
0.0
1
.0
1
1
.0
0
.0
0.0
0
0
Lu
tjan
us syn
ag
ris 0
.2
0.0
9
0.1
1
.3
0.4
3
1
.3
1.6
0
.0
0.0
0
0
O
cyuru
s chrysu
rus
0.3
0
.12
0
.2
1.3
0
.4
4
1.2
1
.4
0.1
0
.11
0
.1
1.0
1
1.0
Lutja
nu
s bu
ccan
ella
1.1
0
.06
0
.5
9.0
1
.1
2
5.7
8
.0
0.0
0
.00
0
Rh
om
bo
plites a
uro
rub
ens
0.2
0
.09
0
.1
1.0
0
.0
3
1.0
1
.0
0.0
0
.00
0
Lutja
nu
s vivan
us
1.6
0
.03
0
.8
26
.0
1
2
6.0
0.0
0
.00
0
Serran
idae
Ep
inep
helu
s mo
rio
0.1
0
.03
0
.0
1.0
1
1.0
0.0
0
.00
0
Myctero
perca
venen
osa
0
.0
0.0
0
0
0
.1
0.1
1
0.1
1
.0
1
1
.0
Ep
inep
helu
s gu
ttatu
s 1
0.9
0
.82
5
.5
6.7
1
.6
27
3
.8
1.5
0
.7
0.2
2
0.6
2
.5
0.8
2
2
.0
4.0
Cep
ha
lop
ho
lis fulva
3
.0
0.6
7
1.5
2
.3
1.3
2
2
1.6
1
.4
0.4
0
.11
0
.3
3.0
1
3.0
Ho
loce
ntrid
ae
Ho
locen
trus a
dscen
sion
is 1
.8
0.2
4
0.9
3
.8
1.3
8
2
.1
2.1
1
.2
0.2
2
0.9
4
.0
1.1
2
2
.6
7.0
Ho
locen
trus ru
fus
0.2
0
.06
0
.1
2.0
0
.7
2
1.7
3
.0
1.3
0
.33
1
.0
3.0
0
.7
3
2.5
2
.6
60
Lan
ded
(#)
D
iscarde
d (#)
%
of
total
p
Me
an
(#)
Me
an
(#)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
(#)
Me
an
(#) no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
Priacan
thid
ae
Pria
can
thu
s aren
atu
s 0
.1
0.0
3
0.0
1
.0
1
1
.0
0
.0
0.0
0
0
A
ulo
stom
idae
A
ulo
stom
us m
acu
latu
s 0
.0
0.0
0
0
0
.3
0.2
2
0.2
1
.0
0.0
2
1
.0
1.0
Dio
do
ntid
ae
Ch
ilom
ycterus a
ntilla
rum
0
.1
0.0
3
0.1
2
.0
1
2
.0
4
.1
0.7
8
3.1
4
.0
1.2
7
2
.3
2.2
Ch
ilom
ycterus a
nten
na
tus
0.0
0
.00
0
0.1
0
.11
0
.1
1.0
1
1.0
Dio
do
n h
olo
can
thu
s 0
.0
0.0
0
0
0
.3
0.1
1
0.2
2
.0
1
2
.0
O
straciidae
A
can
tho
stracio
n p
olyg
on
ia
5.9
0
.55
3
.0
5.4
0
.6
18
4
.5
1.4
1
4.0
0
.67
1
0.6
1
5.8
0
.6
6
13
.3
1.7
Aca
nth
ostra
cion
qu
ad
ricorn
is 0
.2
0.0
6
0.1
2
.0
0.7
2
1
.7
3.0
5
.8
0.8
9
4.3
4
.9
1.0
8
3
.3
1.9
Lacto
ph
rys trigo
nu
s 0
.4
0.1
2
0.2
1
.5
0.4
4
1
.4
1.5
0
.0
0.0
0
0
La
ctop
hrys triq
ueter
0.5
0
.18
0
.2
1.3
0
.4
6
1.3
1
.3
3.1
0
.67
2
.3
3.5
1
.0
6
2.3
2
.2
Lacto
ph
rys bica
ud
alis
1.0
0
.24
0
.5
2.1
0
.9
8
1.6
1
.7
1.0
0
.67
0
.8
1.2
0
.3
6
1.1
1
.3
Balistid
ae
Ba
listes vetula
6
.1
0.7
6
3.0
4
.0
0.8
2
5
3.1
1
.4
0.0
0
.00
0
Mo
nacan
thid
ae
Ca
nth
iderm
is suffla
men
0
.1
0.0
3
0.0
1
.0
1
1
.0
0
.0
0.0
0
0
A
luteru
s scriptu
s 0
.2
0.0
9
0.1
1
.0
0.0
3
1
.0
1.0
1
.8
0.6
7
1.3
2
.0
0.6
6
1
.7
1.7
Ca
nth
erhin
es pu
llus
0.2
0
.03
0
.1
3.0
1
3.0
0.0
0
.00
0
Alu
terus sch
oep
fi 0
.2
0.0
3
0.1
3
.0
1
3
.0
0
.0
0.0
0
0
C
an
therh
ines m
acro
cerus
0.2
0
.09
0
.1
1.0
0
.0
3
1.0
1
.0
1.8
0
.33
1
.3
4.0
1
.1
3
2.6
3
.7
Mu
llidae
P
seud
op
eneu
s ma
cula
tus
3.0
0
.30
1
.5
4.9
0
.7
10
3
.6
1.8
1
.6
0.3
3
1.2
3
.7
1.0
3
2
.5
3.4
61
M
ullo
idich
thys m
artin
icus
0.4
0
.09
0
.2
2.0
0
.5
3
1.8
1
.9
0.4
0
.11
0
.3
3.0
1
3.0
Lan
ded
(#)
D
iscarde
d (#)
%
of
total
p
Me
an
(#)
Me
an
(#)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
(#)
Me
an
(#) no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
(#)
no
n-ze
ro
CI
geo
me
tric
me
an
Gin
glymo
stom
atidae
Gin
glym
osto
ma
cirratu
m
0.4
0
.06
0
.2
3.0
0
.0
2
3.0
1
.0
1.2
0
.44
0
.9
2.0
0
.7
4
1.7
1
.9
Bo
thid
ae
Bo
thu
s lun
atu
s 0
.0
0.0
0
0
0
.1
0.1
1
0.1
1
.0
1
1
.0
Sco
rpae
nid
ae
Ptero
is volita
ns
0.5
0
.06
0
.3
4.5
0
.2
2
4.5
1
.3
0.1
0
.11
0
.1
1.0
1
1.0
62
Land
ed w
eight (g)
Discard
ed
weigh
t (g)
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
Ch
aeto
do
ntid
ae
Ch
eato
do
n stria
tus
0.0
0
.06
7
.3
12
4.2
1
12
4.2
1.7
0
.50
3
05
.1
61
0.2
1
.4
4.0
3
15
.5
3.5
Ch
eato
do
n ca
pistra
tus
0.0
0
.00
0
0.3
0
.13
5
6.4
4
51
.3
1
.0
45
1.3
Ch
eato
do
n o
cellatu
s 0
.0
0.0
0
0
0
.1
0.1
3
10
.5
83
.7
1
.0
83
.7
Po
macan
thid
ae
Ho
laca
nth
us cilia
ris 0
.0
0.0
0
0
1
.7
0.5
0
30
5.5
6
11
.0
0.9
4
.0
48
2.2
2
.1
Po
ma
can
thu
s pa
ru
1.1
0
.12
1
67
.6
14
24
.8
0.1
2
1
42
3.4
1
.1
1.9
0
.25
3
37
.6
13
50
.3
0.3
2
.0
13
11
.7
1.6
Po
ma
can
thu
s arcu
atu
s 0
.0
0.0
0
0
1
.7
0.1
3
29
8.2
2
38
5.3
1.0
2
38
5.3
Ho
laca
nth
us trico
lor
0.1
0
.06
9
.8
16
7.1
1
16
7.1
1.6
0
.38
2
80
.2
74
7.1
0
.7
3.0
5
08
.4
4.3
Acan
thu
ridae
Aca
nth
uru
s coeru
leus
1.7
0
.47
2
72
.0
57
8.0
0
.9
8
44
0.4
1
.7
1.7
0
.38
2
95
.0
78
6.6
0
.5
3.0
7
07
.5
2.0
Aca
nth
uru
s ba
hia
nu
s 1
.8
0.3
5
28
2.4
8
00
.1
1.0
6
4
57
.4
2.8
2
.0
0.6
3
36
2.8
5
80
.5
1.2
5
.0
31
2.1
3
.1
Aca
nth
uru
s chiru
rgu
s 2
.8
0.4
1
43
9.0
1
06
6.1
1
.0
7
60
4.0
2
.6
0.9
0
.50
1
62
.9
32
5.8
1
.0
4.0
2
19
.4
2.8
Caran
gidae
Ca
ran
x rub
er 0
.0
0.0
0
0
1
.5
0.2
5
26
4.8
1
05
9.1
0
.6
2.0
9
71
.3
2.3
Ca
ran
x crysos
4.4
0
.06
7
01
.9
11
93
1.5
1
11
93
1.5
0.0
0
.00
0.0
Sparid
ae
Ca
lam
us ca
lam
us
2.0
0
.24
3
15
.1
13
39
.3
0.7
4
1
03
4.2
2
.4
0.6
0
.13
1
00
.9
80
7.2
1.0
8
07
.2
Table 1
.Fish sp
ecies com
po
sition
of lan
ded
(33
trips) an
d d
iscarded
(8 trip
s) catches w
ith d
escriptive statistics fo
r each sp
ecies taken fro
m n
on
-zero
catches b
ased o
n w
eight (g).
63
Land
ed w
eight (g)
Discard
ed
weigh
t (g)
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
Scaridae
Spa
risom
a virid
e 0
.4
0.1
2
67
.6
57
4.5
0
.1
2
57
3.8
1
.1
0.6
0
.13
1
07
.4
85
9.1
1.0
8
59
.1
Scaru
s taen
iop
terus
1.5
0
.29
2
37
.4
80
7.2
1
.2
5
52
8.2
2
.4
0.4
0
.13
7
0.3
5
62
.1
1
.0
56
2.1
Spa
risom
a a
uro
frena
tum
0
.7
0.2
9
11
8.1
4
01
.4
0.5
5
3
54
.2
1.7
0
.6
0.5
0
10
4.1
2
08
.2
0.5
4
.0
18
5.0
1
.8
Spa
risom
a ch
rysop
terum
1
.2
0.3
5
19
7.9
5
60
.7
0.4
6
5
15
.3
1.5
0
.5
0.1
3
91
.8
73
4.4
1.0
7
34
.4
Hae
mu
lidae
Ha
emu
lon
plu
mierii
20
.8
0.9
4
33
22
.8
35
30
.5
0.9
1
6
21
78
.9
1.8
1
6.0
0
.38
2
86
5.3
7
64
0.9
1
.7
3.0
1
08
5.4
2
0.7
Ha
emu
lon
carb
on
ariu
m
0.1
0
.06
1
7.9
3
04
.4
1
3
04
.4
0
.9
0.1
3
15
2.9
1
22
3.2
1.0
1
22
3.2
Ha
emu
lon
au
rolin
eatu
m
0.1
0
.06
1
9.9
3
37
.7
1
3
37
.7
0
.0
0.0
0
0
.0
Ha
emu
lon
mela
nu
rum
1
.9
0.3
5
30
9.0
8
75
.6
0.9
6
5
95
.8
2.2
1
7.9
0
.50
3
19
2.4
6
38
4.8
1
.8
4.0
1
02
2.2
1
1.0
Ha
emu
lon
alb
um
7
.2
0.2
9
11
46
.0
38
96
.4
0.5
5
3
56
6.9
1
.5
1.0
0
.13
1
75
.0
14
00
.0
1
.0
14
00
.0
Lutjan
idae
Lutja
nu
s jocu
0
.0
0.0
0
0
0
.0
0.0
0
0
.0
Lutja
nu
s ap
od
us
0.5
0
.06
7
3.8
1
25
4.4
1
12
54
.4
0
.0
0.0
0
0
.0
Lutja
nu
s syna
gris
0.0
0
.06
7
.2
12
3.1
1
12
3.1
0.0
0
.00
0.0
Ocyu
rus ch
rysuru
s 0
.4
0.1
2
58
.7
49
8.9
0
.1
2
49
7.8
1
.1
0.2
0
.13
3
2.7
2
61
.6
1
.0
26
1.6
Lutja
nu
s bu
ccan
ella
0.3
0
.06
4
9.2
8
35
.8
1
8
35
.8
0
.0
0.0
0
0
.0
Rh
om
bo
plites a
uro
rub
ens
0.1
0
.06
1
8.1
3
07
.9
1
3
07
.9
0
.0
0.0
0
0
.0
64
Land
ed w
eight (g)
Discard
ed
weigh
t (g)
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
Serran
idae
Epin
eph
elus m
orio
0
.7
0.0
6
10
4.3
1
77
3.2
1
17
73
.2
0
.0
0.0
0
0
.0
Myctero
perca
venen
osa
0
.0
0.0
0
0
0
.5
0.1
3
80
.8
64
6.6
1.0
6
46
.6
Epin
eph
elus g
utta
tus
15
.0
0.7
6
23
98
.6
31
36
.6
1.1
1
3
19
58
.5
1.8
1
.8
0.2
5
32
6.9
1
30
7.8
1
.1
2.0
8
41
.1
7.5
Cep
ha
lop
ho
lis fulva
2
.0
0.5
9
31
1.3
5
29
.2
0.6
1
0
46
3.5
1
.4
0.4
0
.13
7
8.0
6
23
.7
1
.0
62
3.7
Ho
loce
ntrid
ae
Ho
locen
trus a
dscen
sion
is 0
.1
0.1
2
18
.7
15
9.1
0
.2
2
15
7.7
1
.3
0.6
0
.25
1
10
.6
44
2.5
1
.0
2.0
3
21
.5
5.4
Ho
locen
trus ru
fus
0.0
0
.00
0
0.5
0
.38
8
5.7
2
28
.5
1.1
3
.0
15
5.3
3
.3
Priacan
thid
ae
Pria
can
thu
s aren
atu
s 0
.1
0.0
6
21
.3
36
1.6
1
36
1.6
0.0
0
.00
0.0
Au
losto
mid
ae
Au
losto
mu
s ma
cula
tus
0.0
0
.00
0
0.0
0
.13
3
.1
24
.6
1
.0
24
.6
Dio
do
ntid
ae
Ch
ilom
ycterus a
ntilla
rum
0
.0
0.0
0
0
4
.7
0.8
8
84
2.3
9
62
.6
1.0
7
.0
63
9.5
2
.1
Ch
ilom
ycterus a
nten
na
tus
0.0
0
.00
0
0.0
0
.00
0.0
Dio
do
n h
olo
can
thu
s 0
.0
0.0
0
0
0
.9
0.1
3
16
9.5
1
35
6.3
1.0
1
35
6.3
65
Land
ed w
eight (g)
Discard
ed
weigh
t (g)
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
Ostraciid
ae
Aca
nth
ostra
cion
po
lygo
nia
5
.9
0.4
7
93
5.5
1
98
8.0
0
.6
8
16
69
.1
1.6
1
5.0
0
.63
2
67
4.3
4
27
8.9
0
.7
5.0
2
65
1.3
3
.6
Aca
nth
ostra
cion
qu
ad
ricorn
is 0
.1
0.0
6
11
.8
20
1.3
1
20
1.3
4.5
0
.88
7
95
.6
90
9.2
1
.2
7.0
4
57
.6
2.5
Lacto
ph
rys trigo
nu
s 1
.1
0.1
2
17
6.5
1
50
0.4
0
.5
2
14
18
.3
2.0
0
.0
0.0
0
0
.0
Lacto
ph
rys triqu
eter 1
.0
0.1
2
15
2.6
1
29
7.1
0
.3
2
12
71
.1
1.5
2
.0
0.6
3
35
9.9
5
75
.9
1.1
5
.0
32
4.6
2
.9
Lacto
ph
rys bica
ud
alis
0.1
0
.18
2
3.5
1
33
.2
0.3
3
1
29
.8
1.4
0
.9
0.3
8
15
7.0
4
18
.7
0.6
3
.0
36
2.9
2
.2
Balistid
ae
Ba
listes vetula
2
0.8
0
.82
3
32
0.7
4
03
2.3
0
.8
14
2
80
1.1
1
.7
0.0
0
.00
0.0
Mo
nacan
thid
ae
Ca
nth
iderm
is suffla
men
0
.5
0.0
6
87
.5
14
87
.2
1
1
48
7.2
0.0
0
.00
0.0
Alu
terus scrip
tus
0.4
0
.12
6
4.5
5
48
.0
0.1
2
5
47
.3
1.1
0
.3
0.5
0
54
.5
10
9.0
0
.6
4.0
9
4.7
1
.8
Ca
nth
erhin
es pu
llus
0.0
0
.00
0
0.0
0
.00
0.0
Alu
terus sch
oep
fi 0
.3
0.0
6
54
.6
92
8.1
1
92
8.1
0.0
0
.00
0.0
Ca
nth
erhin
es ma
croceru
s 0
.5
0.1
2
85
.6
72
7.6
0
.1
2
72
7.1
1
.1
3.2
0
.38
5
76
.2
15
36
.4
1.4
3
.0
68
2.7
6
.1
Mu
llidae
Pseu
do
pen
eus m
acu
latu
s 0
.2
0.1
2
27
.6
23
4.4
0
.2
2
23
1.3
1
.4
1.3
0
.38
2
29
.9
61
3.0
1
.1
3.0
3
89
.4
4.0
Mu
lloid
ichth
ys ma
rtinicu
s 0
.1
0.0
6
23
.6
40
0.4
1
40
0.4
0.8
0
.13
1
41
.7
11
33
.4
1
.0
11
33
.4
66
Land
ed w
eight (g)
Discard
ed
weigh
t (g)
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
%
of
total
p
Me
an
we
ight
(g)
Me
an
we
ight
(g)
no
n-
zero
CV
no
n-
zero
N
no
n-
zero
catche
s
Ge
om
etric
me
an
we
ight (g)
no
n-ze
ro
CI
geo
me
tric
me
an
Gin
glymo
stom
atidae
Gin
glym
osto
ma
cirratu
m
1.9
0
.06
2
97
.8
50
62
.4
1
5
06
2.4
8.7
0
.38
1
56
2.9
4
16
7.7
1
.2
3.0
2
44
6.3
4
.1
Bo
thid
ae
Bo
thu
s lun
atu
s 0
.0
0.0
0
0
0
.3
0.1
3
45
.0
35
9.6
1.0
3
59
.6
Scorp
aen
idae
Ptero
is volita
ns
0.0
0
.00
0
0.0
0
.00
0.0