Rbm

JDa

Hb

1c

d

a

ARRA

KDRPTU

1

tmssrieeu

hs

mN

0h

Fisheries Research 147 (2013) 304– 311

Contents lists available at ScienceDirect

Fisheries Research

jou rn al hom ep age: www.elsev ier .com/ locate / f i shres

elative trap efficiency for recreationally caught eastern Australianlue swimmer crab (Portunus pelagicus) and associated injury andortality of discards

esse C. Lelanda,b,∗, Paul A. Butchera, Matt K. Broadhursta, Brian D. Patersonc,avid G. Mayerd

New South Wales Department of Primary Industries, Fisheries Conservation Technology Unit, National Marine Science Centre, P.O. Box 4321, Coffsarbour, NSW 2450, AustraliaMarine Ecology Research Centre and National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box57, Lismore, NSW 2480, AustraliaDepartment of Agriculture, Fisheries and Forestry, Bribie Island Research Centre, P.O. Box 2066, Woorim, QLD 4507, AustraliaDepartment of Agriculture, Fisheries and Forestry, Ecosciences Precinct, GPO Box 267, Brisbane 4001, Australia

r t i c l e i n f o

rticle history:eceived 12 October 2012eceived in revised form 18 June 2013ccepted 11 July 2013

eywords:

a b s t r a c t

Australian recreational fishers targeting Portunus pelagicus are regulated by unverified gear restrictionswhich, combined with size, sex and quota regulations, result in >40% of their catches being discarded; allwith unknown fate. To address these issues, we investigated the relative efficiency and temporal selec-tivity of “round”, “rectangular” and “wire” pots, and “hoop nets” set for 3, 6, and 24 h and the subsequentinjury, physiological stress and mortality (in cages with controls over three days) of discarded P. pelagi-

iscardingelative efficiencyortunus pelagicusrapnaccounted fishing mortality

cus (37–85 mm carapace length – CL). Undersized (<60 mm CL) and ovigerous P. pelagicus comprised 22%and 4% of the total catch. Irrespective of soak time, round pots caught significantly more P. pelagicus andteleost bycatch. Five percent of individuals lost 1–3 appendages, usually during disentanglement, andonly 1.1% of discarded P. pelagicus died (all within 24 h). Haemolymph parameters were mostly affectedby biological, rather than technical factors. The results support the mandatory discarding of P. pelagicus,but pot selectivity might be improved via escape vents or larger mesh sizes.

. Introduction

For many exploited aquatic species, unaccounted fishing mor-ality can represent a substantial component of their total fishing

ortality and so accurate estimation is essential for effectivetock management (ICES, 2005; King, 2007). More than sixub-components of unaccounted fishing mortality have beenecognised. However, most attention has focused on the mortal-ty caused during discarding (or “release”); not only because suchstimates often are the easiest to acquire, but also because gen-rally they are assumed to comprise the greatest proportion ofnaccounted deaths (Broadhurst et al., 2006a).

Among recreational fisheries, most discard mortality studiesave involved teleosts, reflecting not only concerns about effort andubsequent stock sustainability, but also the welfare of survivors

∗ Corresponding author at: Marine Ecology Research Centre, School of Environ-ent, Science and Engineering, Southern Cross University, P.O. Box 157, Lismore,SW 2480, Australia. Tel.: +61 2 6620 3786; fax: +61 2 6621 2669.

E-mail address: jesse.leland@scu.edu.au (J.C. Leland).

165-7836/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.fishres.2013.07.006

© 2013 Elsevier B.V. All rights reserved.

(Bartholomew and Bohnsack, 2005; Arlinghaus et al., 2007). Untilrecently, much less attention had been directed towards assessingthe fate of recreationally discarded crustaceans (Parsons andEggleston, 2005; Butcher et al., 2012; Leland et al., 2013); perhapsowing to their relatively greater resilience to associated stressors(Wassenberg and Hill, 1993) and/or their perceived inability to feelpain (Elwood et al., 2009).

Like teleosts, crustacean discard mortality can be directly esti-mated over the short term (Wassenberg and Hill, 1993; Broadhurstet al., 2009), although finer-scale analyses of physiological impactsare also required to assess the potential for delayed mortality(Uhlmann et al., 2009; Leland et al., 2013). Specifically, quanti-fying haemolymph constituents can identify changes in internalhomeostasis (Poole et al., 2008; Uhlmann et al., 2009), whichoften correlate with discard-related stressors (e.g. air exposure andappendage loss) that can alter immunocompetence. Deviation fromnormal physiological function can be identified by quantifying the

proportions of circulating haemocytes (Perazzolo et al., 2002), clot-ting time (Jussila et al., 2001), protein (by refractive index – RI) (Dall,1975), glucose (Butcher et al., 2012) and lactate (Leland et al., 2013).Such parameters can provide useful indices of possible longer-term

Resea

it2is

ttstm(ascP

(fi“ai(bu

apmps

J.C. Leland et al. / Fisheries

mpacts (e.g. infection), although the associated cost–benefit rela-ionships must be considered (Jussila et al., 2001; Uhlmann et al.,009). Therefore, the consideration of previously applied measures

s warranted; the utilities of which are often species- or procedure-pecific (Uhlmann et al., 2009; Butcher et al., 2012).

Australian recreational fishers target various marine crus-aceans (Henry and Lyle, 2003; King, 2007). One species for whichhere are concerns about unaccounted fishing mortality is the bluewimmer crab (Portunus pelagicus), which is widely distributedhroughout the Indo-West Pacific (Lai et al., 2010). Recently, using

orphometric, morphological and genetic characteristics, Lai et al.2010) revised P. pelagicus into four species, including Portunusrmatus, Portunus reticulatus and Portunus segnis. However, for con-istency, and because this revision did not assess reproductiveompatibility and was not conclusive, in this study we report on. pelagicus.

P. pelagicus are distributed throughout all Australian statesexcept Tasmania and Victoria), and are targeted by recreationalshers; predominantly using traps (which include both enclosedpots” and open “hoop nets” – Fig. 1). Recently, “round” and “rect-ngular” collapsible pots have been introduced and their popularitys increasing among both recreational and commercial fishersCampbell and Sumpton, 2009; Butcher et al., 2012; Fig. 1a and), although the traditional rigid “wire” pots and hoop nets are stillsed (Fig. 1c and d).

Owing to input control regulations (e.g. trap type, dimensionsnd mesh size, and minimum legal size, sex limits and quotas for P.

elagicus), >40% of the national recreational P. pelagicus catch (∼3.9illion individuals p.a.) is discarded, representing the greatest pro-

ortion for any local crustacean (Henry and Lyle, 2003). Despiteuch discarding, few studies have assessed either the relative

Fig. 1. Diagrams and dimensions of (a) round, (b) rectangular and (c) wire

rch 147 (2013) 304– 311 305

selectivity (i.e. for legal P. pelagicus) or efficiency (i.e. for total P.pelagicus catch) of existing recreational traps (to validate mesh sizesand/or configurations – but see Bellchambers and de Lestang, 2005;Boutson et al., 2009), or the associated damage and mortality ofdiscards. Accurately quantifying mortality among discarded under-sized and ovigerous individuals is required for stock assessments(King, 2007).

It is well established that P. pelagicus caught and discarded fromcommercial trawls and gillnets can be injured and subsequently die,although the estimated impacts vary (Wassenberg and Hill, 1989,1993; Broadhurst et al., 2009; Uhlmann et al., 2009). For example,Broadhurst et al. (2009) observed minimal injuries and low mortal-ity (6%) among mature P. pelagicus discarded from gillnets after upto 2.5 h of air exposure. Uhlmann et al. (2009) reported that man-ually removing appendages from juvenile P. pelagicus (<25 mm CL)during disentanglement and discarding caused unsealed wounds,increased haemolymph loss and treatment-specific mortalities ofup to 50%. Although similar wound data were not collected fortrawled-and-discarded P. pelagicus, Wassenberg and Hill (1989,1993) reported that up to 51% were injured (1–3 appendages miss-ing) and mortalities approached 15%. These studies provide someevidence of a broad correlation between the extent of woundingand mortality.

Beyond the potential for some wounding among recreation-ally trapped-and-discarded P. pelagicus, there are other concerns.In particular, ovigerous P. pelagicus occur throughout the fishingseason (in all relevant states) and their abundances generally peak

during early summer (e.g. Potter and de Lestang, 2000; Johnsonet al., 2010), before they leave the estuaries to spawn (Potter andde Lestang, 2000). Although size, quota and sex regulations vary,discarding is mandated in all states. Further, ovigerous female

pots and (d) hoop nets used to target Portunus pelagicus in Australia.

306 J.C. Leland et al. / Fisheries Research 147 (2013) 304– 311

Table 1Technical specifications for round, rectangular and wire pots, and hoop nets used to target Portunus pelagicus.

Traps Mesh Entrance

Material Shape Material Ø (mm) Nominal SMO (mm) Type n Dimensions (cm)

Hoop net Polyamide monofilament Diamond 0.5 150 Open mesh 1 750 ØWire pot Steel wire Rectangular 2.0 75 Open funnel 2 30 × 15Rectangular pot Polyethylene multifilament Square 1.0 90 Open ‘V’-shaped funnel 2 55 × 28

S

da

tattti

2

2

(Ac“pmwaibam∼3

2

cupfiptdt

(ads–mcooaaou

Round pot Polyethylene multifilament Diamond 1.0

MO, stretched mesh opening; Ø, diameter; n, number of entrances.

iscards may have an increased propensity for fishing-related dam-ge (see Bellchambers et al., 2005).

Given the above, the aims of this study were first to determinehe relative selectivity and temporal efficiency of common recre-tional traps targeting P. pelagicus. Second, we sought to investigatehe potential for physical injury, physiological effects and short-erm mortality of discarded P. pelagicus (with particular attentiono undersized and ovigerous individuals) and also the immediatempacts to teleost bycatch.

. Materials and methods

.1. Study location and traps used

The study was done within a ∼7 km2 radius in Wallis Lake32◦19′18′′S, 152◦30′10′′E); an estuary in New South Wales (NSW),ustralia. Starting 16 November 2010, fifteen replicates of fourommon recreational P. pelagicus traps were used: (i) collapsibleround pots”; (ii) collapsible “rectangular pots”; (iii) rigid “wireots”; and (iv) “hoop nets” (Fig. 1 and Table 1). All traps had theireshes measured (inside stretched mesh opening – SMO) to ensureithin treatment uniformity, and were submerged in a similar estu-

ry for >3 h before use to reduce the potential for confoundingmpacts on efficiency. On each fishing day (n = 14), the traps wereaited with ∼0.5 kg of sea mullet (Mugil cephalus) placed inside

wire-mesh bait bag (250 mm × 200 mm, with 10 mm × 10 mmesh), before five replicates of each were set at random locations50 m apart to ensure independence (Williams and Hill, 1982) for, 6 and 24 h.

.2. Experimental protocol

After each trap was retrieved, P. pelagicus and bycatch wereoncurrently removed, with the former being either emptied orntangled, and the time taken for these processes recorded. Non P.elagicus bycatch (i.e. teleosts and other crustaceans) were identi-ed, measured (for CL or total length – TL, nearest 1.0 mm), sexed ifossible, classified as alive or dead (i.e. responsive or unresponsiveo an external stimulus) and then released. Traps were assessed foramage (i.e. broken meshes) after each retrieval and any damagedraps were repaired or replaced.

All trapped P. pelagicus were measured with vernier callipersnearest 1.0 mm) for CL (the distance between the frontal notchnd the posterior carapace margin) and carapace width (CW – theistance between the tips of the ninth antero-lateral spines). Moulttage was assessed following Hay et al. (2005): (i) early inter-moult

moderately flexible shell and some wear on chelae; (ii) late inter-oult – little or no flex in shell, and/or large, significant wear on

helae; or (iii) post-moult – clean and highly flexible shell, no wearn chelae. Sex was assessed, with the reproductive condition (i.e.vigerous or non-ovigerous) of females noted. The pleonal flap of

ll P. pelagicus, and ovaries from visibly ovigerous females, weressessed for macroscopic damage. If present, the length (1.0 mm),r volume (mm3) of the affected areas were recorded. Individ-als were categorised as either “intact” (undamaged), “injured”

50 Semi-closed funnel 4 30 × 20

(damaged appendages, carapace, pleonal flap or ovaries), or “previ-ously damaged” (damage unrelated to our trapping). The position,type and number of any missing appendages (i.e. chelae, pereopodsand swimmerets) were determined and these injuries were classedas “sealed” or “unsealed” following Uhlmann et al. (2009). Someintact P. pelagicus (37–72 mm CL) were immediately (within 20 s)sampled for haemolymph (see Section 2.3 below) following Butcheret al. (2012). Owing to insufficient numbers (for statistical analysis),injured individuals were not bled.

All P. pelagicus were then placed into individual 20 l polyvinylchloride containers (PVC – 300 cm diameter (Ø) × 400 cm depth)with 18 mm Ø holes in the sides (n = 15) and lids (n = 5) to facilitatewater exchange (termed “cages”; see Butcher et al., 2012) and theirintervening handling time (“removal time”) recorded. The cageswere immediately transported to a monitoring site (in the lake),where each was attached (∼1 m apart) to a 300 m bottom-set line(in <2 m depth). During the experiment, other intact P. pelagicus(37–76 mm CL) were caught at night in <2 m depth using a spot-light and knotless PVC net, transported to the monitoring site andused as controls. Some undersized controls were also immediatelysampled for haemolymph (see Section 2.3 below) prior to beingcaged.

All trapped-and-discarded and control P. pelagicus were mon-itored in the cages for three days. Any individuals that moultedor died during this period were noted, with the latter immedi-ately removed. All survivors (i.e. trapped and control) were releasedwith the distal tip of the left epipodite (from the first maxilliped)removed to facilitate identifying recaptures during the study. Thismethod was chosen instead of t-bar tagging because the latter oftencauses mortality (McPherson, 2002).

2.3. Haemolymph sampling

All haemolymph samples were taken through the ventral sinusof either fifth pereopod using a small-gauge syringe. Non-repetitivesamples were taken from a subset of the trapped-and-discardedand control P. pelagicus; either immediately after trapping (termed“day 0”) or at the end of monitoring (termed “day 3”). Haemolymphsamples were subsequently assessed for total (THC – ×105) anddifferential haemocyte counts (DHC – ×105) using a NEUBAURTM

haemocytometer under light microscopy (at 100×) and the differ-entiation technique outlined by Butcher et al. (2012). Refractiveindex (Leavitt and Bayer, 1977) was determined using a VetQuipTM

VQ5600 refractometer and converted to protein (mg ml−1) follow-ing the procedures outlined by Butcher et al. (2012). Haemolymphsamples were frozen in liquid nitrogen for subsequent analysis ofglucose (mM) and lactate (mM) using an OLYMPUSTM AU400 auto-mated clinical analyser and clotting time (s) was quantified withthe modified capillary tube method of Jussila et al. (2001) (see alsoLeland et al., 2013).

2.4. Data analyses

Generalised linear mixed models (GLMM) or general linearmodels (GLM) (McCullagh and Nelder, 1989) were appropriately

J.C. Leland et al. / Fisheries Research 147 (2013) 304– 311 307

Table 2Summary of fixed factors analysed with generalised linear models to explain vari-ability in absolute and proportion undersized (<60 mm CL), legal (≥60 mm CL) andtotal Portunus pelagicus catches, and teleost bycatch, from four trap types set for 3,6 and 24 h soak times.

Portunus pelagicus

Absoluteundersized

Proportionundersized

Legal Total Teleostbycatch

Fixed factorTrap type (T) *** * *** *** ***

Soak time (S) *** ns *** *** ***

T × S *** ns * * ns

n

aGadahFad(vf

mtctu

PecAecaT

3

3

6gtl0bs

tstmfapmT

0

0.5

1.0

1.5

2.0

0

0.1

0.2

0.3

0.4

Trap and soak time (h)

3 6 24

0.4

0.8

1.2

1.6

3 3 36 6 624 24 24

(a) Total P. pelagicus

(b) Absolute undersized P. pelagicus (< 60 mm CL)

(c) Legal P. pelagicus (≥ 60 mm CL)Adj

uste

d m

ean

no. o

f P. p

elag

icus

per

trap

a

bc c c dc d ed e fd e f e f g f gg g

a

b

a

bc cc d

fc d

d e e f e ff f

b cb ccdd d d d d d

0

Round pot Rectangular Wire pot Hoop netpot

Fig. 2. Mean (a) total, (b) absolute undersized and (c) legal catches of Portunuspelagicus by round, rectangular and wire pots, and hoop nets set for 3, 6 and 24 h

significantly greater than those from all wire-pots and hoop-nets(t-test, p < 0.05; Fig. 2b). Compared with round and rectangularpots, hoop nets caught proportionally fewer undersized P. pelagicus

0

7

14

21

28

35

Rectangular Wire pot Hoop net

Per

cent

age

(%)

a

a

a b

b

s, not significant.* p < 0.05.

*** p < 0.001.

pplied, using the GLMM procedure from GenStat (2010). WhereLMMs were not converged because of sparse (or extreme) data,

simplified GLM was adopted. We tested the hypothesis of noifferences in: (i) relative efficiency for P. pelagicus and teleostsmong the four treatment traps; and (ii) physical damage; and (iii)aemolymph constituents among trapped and control P. pelagicus.ixed factors included “treatment of P. pelagicus” (i.e. trapped-nd-discarded or control crabs), “trap type”, “soak time” (i.e.eployment duration), “day sampled”, “CL”, “moult stage” and “sex”and interactions where appropriate). To encompass the temporalariability in sampling, “capture date” was included as a randomactor in all relevant models.

Parametric models with the normal distribution (and transfor-ation when necessary) were suitable for most parameters, but

he Poisson (with a log-link) and logistic models were used forounts and binomial data, respectively. Where significant fixed fac-ors exceeded two levels, differences among means were exploredsing post hoc t-testing with the GenStat (2010) RPAIR procedure.

The independence of the treatment (trapped vs. controls) of. pelagicus and the total numbers surviving at the end of thexperiment was investigated using the Fisher’s exact test. Pearson’shi-square test was used to analyse contingency tables of counts.djusted means (± SE for normal models only) are presented underqual weighting from all terms in the models. Undersize P. pelagicusatches were analysed as both absolute (i.e. number of undersize)nd proportional values (i.e. percentage undersize per trap type).he null hypotheses were rejected at p < 0.05.

. Results

.1. Relative trap selectivity and temporal efficiency

In total, 277 P. pelagicus were caught (37–85 mm CL), of which1 (22%) were undersized (37–59 mm CL) and 10 (4%) were ovi-erous (62–72 mm CL). Irrespective of soak time, round pots werehe most efficient (predicted mean of 0.89 individuals per trap), fol-owed by rectangular pots, hoop nets and wire pots (0.20, 0.17 and.07 individuals per trap). No significant associations were foundetween trap type and sex ratio (�2 = 4.72, df = 3; p > 0.05), or moulttage (�2 = 3.73, df = 6; p > 0.05).

Catches of undersized (absolute and proportional), legal andotal P. pelagicus varied significantly among trap types and withinoak times (GLM, p < 0.05; Table 2 and Fig. 2). Specifically, comparedo all other traps, round pots set for 6 and 24 h caught significantly

ore individuals in all categories (except for rectangular pots setor 6 and 24 h) (t-test, p < 0.05; Fig. 2a–c). Within trap types, round

nd rectangular pots set for 24 h caught significantly more total P.elagicus than those set for 3 and 6 h, while hoop nets reached theiraximum efficiency after being set for 6 h (t-test, p < 0.05; Fig. 2a).

otal catches for wire pots were similar, irrespective of soak time

(n = 5 replicate traps per soak time). Dissimilar letters indicate significant differences(t-test, p < 0.05).

(t-test, p > 0.05; Fig. 2a). Absolute undersized catches from roundand rectangular pots set for 6 h were similar (t-test, p > 0.05) and

Round potpot

Fig. 3. Percentage catches of undersized Portunus pelagicus from the four trap types.Dissimilar letters indicate significant differences (t-test, p < 0.05).

308 J.C. Leland et al. / Fisheries Research 147 (2013) 304– 311

Table 3Total number (n) and mean total length (TL in mm ± SD, where relevant) of teleosts caught with each trap.

Traps

Round pot Rectangular pot Wire pot Hoop net

n TL n TL n TL n TL

TeleostsToadfish (Tetractenos spp.) 34 156 ± 18 1 148 – – – –Yellowfin bream (Acanthopagrus australis) 20 137 ± 18 2 133 ± 17 – – –Tarwhine (Rhabdosargus sarba) 20 129 ± 12 – – – – – –Silver biddy (Gerres subfasciatus) 1 50 – – – – – –Striped catfish (Plotosus lineatus) 1 344 – – – – – –Leather jackets (Monocanthus spp.) – – 11 257 ± 46 5 279 ± 102 2 330 ± 113Dusky flathead (Platycephalus fuscus) – – – – – – 1 380

–

–

(a

c(bttbOo

3

pnnpp

1apnppaoitr(

c(tTa

3

mmfsou

and rectangular pots (0.66 and 0.56 mM), and hoop nets (0.60 mM)(t-test, p < 0.05; Fig. 4a). P. pelagicus caught with wire and rectangu-lar pots had significantly greater protein concentrations (75.19 and60.02 mg ml−1) than those from round pots and hoop nets (46.57

Control Round pot Rectangular Wire pot Hoop net

(a)

(b)

Lact

ate

(mM

)P

rote

in (m

g m

l )-1

bb

b

a

a

a

b b bb

2.0

1.5

1.0

0.5

0

80

60

40

20

0

pot

Large tooth flounder (Pseudorhombus arsius) – –

, none caught.

t-test, p < 0.05; Fig. 3), while wire pots caught the same proportions all other designs (t-test, p > 0.05; Fig. 3).

The total non P. pelagicus bycatch comprised three giant mudrab (Scylla serrata – 84, 88 and 96 mm CL), and eight teleost speciesn = 101; Table 3) and was significantly, and independently, affectedy trap type and the soak time (GLMM, p < 0.001; Table 2). Irrespec-ive of soak time, round pots caught more teleosts than the otherraps (t-test, p < 0.05). For all traps combined, the amount of teleostycatch was positively correlated with soak time (t-test, p < 0.05).nly one individual (tarwhine, Rhabdosargus sarba) died, and wasbserved being eaten by a P. pelagicus in a wire pot.

.2. Trap clearance and injuries to discards

The time required to clear traps was significantly affected by P.elagicus entanglement (mostly in hoop nets) (GLM, p < 0.001), butot soak time (GLMM, p > 0.05). Compared with all other traps, hoopets were significantly more likely to have meshes broken (t-test,

< 0.05), with 1.3 ± 0.3 10.6 ± 0.3 and 5.7 ± 1.1 damaged mesheser trap set for 3, 6 and 24 h, respectively.

Only 15 (5%) P. pelagicus (52–79 mm CL) were injured (with–3 missing appendages, pleonal flap and/or ovarian damage)nd of these, six had unsealed wounds (to their appendages orleonal flaps). The wounded included one ovigerous and threeon-ovigerous females and 10 males (two were undersized). P.elagicus were never entangled (i.e. restricted by meshes) in wireots, but this occurred in round (10%) and rectangular pots (41%),nd hoop nets (94%), with respective mean disentanglement timesf 23.0 ± 4.5, 58.4 ± 16.7 and 99.4 ± 12.5 s. Two round pot trappedndividuals had damaged pleonal flaps with 15 mm of the distalip missing; injuries that occurred during the soak and removal,espectively. The only ovigerous female with damaged ovaries∼10 mm3) was hoop netted.

There were no significant effects of trap type or soak time onhelae, pereopod and swimmeret injuries, nor total appendage lossGLMM, p > 0.05). There were no significant interactions betweenrap types and their soak time on injuries (GLMM, p > 0.05).welve percent of the catch had previous damage (1–3 missingppendages). No discarded P. pelagicus were recaptured.

.3. Mortality and monitoring

None of the control and only three trapped P. pelagicus died (allales and within 24 h of discarding), providing a non-significantortality of 1.1% (Fisher’s exact test, p > 0.05). Two fatalities were

rom hoop nets set for 6 and 24 h, and one was from a round potet for 24 h. None of the three mortalities lost appendages, butne had an injured pleonal flap (with loss of anal tissue and annsealed wound) and one sustained internal trauma (i.e. caused by

– 3 274 ± 80 – –

concussion during measurement), while the other was uninjured.Removal times for these individuals were 2, 45 and 95 s. None of themonitored ovigerous P. pelagicus had changes in their ovarian con-dition, and all individuals vigorously swam away when released.Three non-ovigerous females (one injured) moulted during moni-toring.

3.4. Haemolymph parameters

A preliminary GLMM showed no significant interaction betweenthe treatment of P. pelagicus (control and trapped combined) andthe day sampled for any haemolymph parameters (p > 0.05). Thetreatment of P. pelagicus significantly affected their lactate and pro-tein concentrations (GLM and GLMM, p < 0.05; Table 4). Specifically,mean lactate was significantly greater in P. pelagicus caught withwire pots (1.79 mM), than controls (0.60 mM) and those from round

Fig. 4. Concentrations of haemolymph (a) lactate and (b) protein for control Por-tunus pelagicus and those caught by round, rectangular and wire pots, and hoop nets(across all soak times and sampling periods). Dissimilar letters indicate significantdifferences (t-test, p < 0.05).

J.C. Leland et al. / Fisheries Research 147 (2013) 304– 311 309

Table 4Summary of fixed factors tested in generalised linear (lactate and clotting time only) and mixed models for significant effects on haemolymph parameters among all monitoredPortunus pelagicus and then only those that were trapped.

Haemolymph parameters

THC DHC Protein Glucose Lactate Clotting ability Clotting time

All P. pelagicusTreatment of P. pelagicus ns ns ** ns * ns nsDay sampled ns *** ns *** *** ns ns

Trapped P. pelagicusCL ns * ns ns ns ns nsMoult stage ns ns ** ** ns ns nsSex ns ns ns ns ns * *

Day sampled * *** ns *** *** ns ns

THC, total haemocyte count; DHC, differential haemocyte count; CL, carapace length; ns, not significant.* p < 0.05.

aF

ltpswd

ahtwt(pis5tscTcte

4

taratite

eo2wwsw

** p < 0.01.*** p < 0.001.

nd 37.67 mg ml−1), and controls (42.12 mg ml−1) (t-test, p < 0.05;ig. 4b).

Irrespective of the treatment of P. pelagicus, their glucose andactate concentrations and DHC varied significantly between thewo sampling days, and all by similar magnitudes (GLM and GLMM,

< 0.05; Table 4). Glucose was significantly greater in P. pelagicusampled on day 3, than those sampled on day 0 (0.5 vs. 0.3 mM),hile both lactate and DHC were significantly greater on day 0 thanay 3 (1.1 vs. 0.6 mM and 12.2 vs. 6.8 × 105) (t-test, p < 0.05).

A reduced GLMM (i.e. omitting the controls) was used tossess the influence of biological factors and sampling day on theaemolymph parameters of only trapped P. pelagicus. Differen-ial haemocyte counts were significantly and positively associatedith CL (GLMM and t-test, p < 0.05; Table 4). Glucose and pro-

ein concentrations were significantly influenced by moult stageGLMM, p < 0.01; Table 4), with the former significantly greater forost-moults (0.43 mM) and late inter-moults (0.50 mM), than their

nter-moult conspecifics (0.35 mM – t-test, p < 0.05). Protein wasignificantly greater in inter-moults and late inter-moults (53.7 and8.2 mg ml−1), than in post-moult individuals (40.0 mg ml−1 – t-est, p < 0.05). Haemolymph clotting was significantly affected byex (GLM and GLMM, p < 0.05; Table 4) and was proportionally lessommon (58 vs. 92%), and took longer (23.9 vs. 52.9 s) for females.he day sampled significantly influenced glucose and lactate con-entrations, THC and DHC – following the same trends as those inhe complete models (t-test, p < 0.05; GLMM, p < 0.001; Table 4),xcept for THC, which was greater in day 0 samples.

. Discussion

This study represents the first assessment of the relative selec-ivity and temporal efficiency of recreational traps for P. pelagicus,nd the concomitant impacts to discards. While the low injuryates and mortality of discarded P. pelagicus validate existing man-gement practices for controlling exploitation, simple changes tohe design and/or operation of traps could minimise unwantedmpacts. Relevant modifications can be identified by consideringhe potential mechanisms contributing towards the observed trapfficiency, and the subsequent effects on discards.

The efficiency of portunid traps is particularly sensitive tontrance design, but typically those with multiple, semi-closedpenings are the most effective (Vazquez Archdale et al., 2006,007; Butcher et al., 2012). The same trend was observed here,

ith relatively greater catches in round pots; a characteristic thatas also probably affected by their shape and/or small mesh

ize (Butcher et al., 2012). More specifically, because these trapsere circular, all of the semi-closed entrances were close together

(only ∼200 mm apart), maximising bait access. Further, althoughthe SMO of round pots measured ∼50 mm (Table 1), their lateralopenings were considerably smaller (only ∼10–15 mm) and corre-sponded to the maximum width of a ∼110 mm TL yellowfin bream,Acanthopagrus australis (Broadhurst et al., 2006b). Given the meansizes of retained A. australis (∼140 mm TL – Table 3), and other mor-phologically similar species (i.e. R. sarba and silver biddy, Gerressubfasciatus), and the fact that mesh openings were smaller thanthe narrowest observed P. pelagicus carapace depth, it is unlikelythat many similar- or larger-sized teleosts, or P. pelagicus escapedfrom round pots.

Similarly, although rectangular pots were less efficient thanround pots, which was probably due to fewer and more openentrances, their lateral mesh openings were also considerably lessthan their SMO (i.e. 50 vs. 90 mm). Such an effect probably explainsthe relatively larger proportions of undersized P. pelagicus andteleost bycatch retained by rectangular traps. Boutson et al. (2009)found that escape vents in collapsible rectangular pots (similar tothose used here) reduced undersized P. pelagicus catches, and otherbycatch (by 59% and 38%, respectively) without affecting legal-size catches. Similar modifications and/or increases in mesh sizeat strategic locations in the pots assessed here might improve theirselectivity.

In addition to technical modifications, simply regulating thesoak time of hoop nets could reduce their environmental impacts;both in terms of size selectivity and also the potential for lostnetting. In this study, hoop nets were more selective than potsfor legal-sized P. pelagicus, with maximum efficiency achieved atsome point before 6 h. Such results may indicate density-dependantchanges to entry or escape rates, probably because of the relativelysmall surface area (i.e. ∼750 cm Ø × 300 cm) and the associated riskof antagonistic interactions among netted conspecifics (Smith andHines, 1991). It is also possible that, owing to the large mesh size(i.e. ∼150 mm), some small P. pelagicus were less securely entangledand were able to escape. Butcher et al. (2012) reported similar selec-tivity for hoop-netted S. serrata. Given the similarities in hoop-netselectivity among often sympatrically distributed NSW portunids,soak-time restrictions (e.g. <3 h) would reduce the potential forimpacts from damaged hoop nets, while having minimal effectson catches.

Another consideration regarding hoop nets is the possibility ofinjuries, particularly among ovigerous females. In this study, 10 ovi-gerous females were caught and while only one was damaged, itwas hoop netted. Injuries to P. pelagicus ovaries have been identi-

fied previously (see Bellchambers et al., 2005), but detailed studiesare lacking. Given the substantial spatial and temporal variationreported for ovigerous P. pelagicus (Bellchambers and de Lestang,2005; Johnson et al., 2010) and the prevalence of mature females

3 Resea

idi

mdseg((fpteaao2

smretwcclmc

fgT2heieia2c

aFvtasiwtbace2

dmost(

10 J.C. Leland et al. / Fisheries

n trap catches (Smith et al., 2004), future research is warranted toetermine if a stronger bias towards injuries exists among these

ndividuals.Hoop nets were not the only trap that injured P. pelagicus, and

ost appendage loss occurred during disentanglement. The ten-ency for crustaceans to autotomise appendages, as an escapetrategy, is well known (e.g. Smith and Hines, 1991; Wassont al., 2002) and although the subsequent changes to P. pelagicusrowth rate are generally transitory, overall growth can be reducedPaterson et al., 2007). Autotomy was observed in the current study57% of injuries), but less frequently than for S. serrata discardedrom the same traps by Butcher et al. (2012). P. pelagicus are com-aratively less likely to autotomise appendages during handling,hus disentanglement can result in unsealed injuries (Uhlmannt al., 2009). Nevertheless, only 15% of all P. pelagicus were injurednd very few died, a relationship that supports previous studiesssessing the short-term fate of this species after discarding fromther gears (Wassenberg and Hill, 1989, 1993; Broadhurst et al.,009; Uhlmann et al., 2009).

The observed physiological responses of trapped P. pelagicusuggests few protracted impacts and/or mortalities beyond theonitoring period. For example, compared to previously reported

anges for P. pelagicus (Uhlmann et al., 2009) and S. serrata (Poolet al., 2008; Butcher et al., 2012), the observed lactate and pro-ein concentrations in this study were low. Further, the effect ofire traps on lactate was caused by substantially elevated con-

entrations (∼2 and 4 times greater) for two outliers. Individualsaught with rectangular and wire pots had relatively greater, andess competitive, bait access (without risk of entanglement), which

ay have lengthened the time for metabolic processes and theorresponding increase in haemolymph protein (Dall, 1975).

Nevertheless, post-trapping THC, and sex-specific clotting dif-erences indicated that some stress occurred. Although stressenerally reduces haemocyte counts (Uhlmann et al., 2009), initialHC elevations for crustaceans have been reported (Pascual et al.,003; Leland et al., 2013). The temporary increases in THC observedere were attributed to within-trap cardiovascular activity (Jussilat al., 2001; Leland et al., 2013), and may have been affected byntra-specific aggression. Aggressive behaviour may also partiallyxplain the observed clotting impairments among female P. pelag-cus, which have not been reported previously and are probablylso indicative of stress (see Jussila et al., 2001; Uhlmann et al.,009). Such changes may be important because they potentiallyould increase post-discard haemolymph loss and predation.

Most of the remaining haemolymph parameters were moreffected by experimental and/or biological factors than trapping.or example, irrespective of treatment, DHC, glucose, and lactatearied between the two sampling times (and by similar magni-udes) – probably in response to caging and the subsequent reducedctivity (for glucose and lactate) along with some confinementtress (Dall, 1975; Taylor et al., 2009). Given that only intact P. pelag-cus were sampled, it is unlikely that observed alterations in DHC

ere indicative of an immunological response to trauma (or infec-ion) (Perazzolo et al., 2002). Further, the observed relationshipetween CL and DHC, and lower protein and glucose concentrationsmong post- and inter-moult P. pelagicus, probably were related toyclic changes associated with moulting (Dall, 1975; Chang, 1995);ffects that have been reported for other crustaceans (Butcher et al.,012; Leland et al., 2013).

While the observed stress, injury and short-term mortality toiscarded P. pelagicus in this study were all low, further researchay be required to quantify other potential unwanted impacts

f trapping. In particular, the greater relative efficiency and poorelectivity of round pots demonstrates a disparity between designshat affects discarding and effort regulation in the relevant statesi.e. NSW, Queensland and the Northern Territory). Further, owing

rch 147 (2013) 304– 311

to their performance, the popularity of round pots among bothrecreational and commercial fishers is exceeding that of otherdesigns and assessing their ghost-fishing potential (i.e. before andafter modification) is a priority. Such work should also encom-pass the other traps, particularly hoop nets. The indirect impactsof derelict traps may represent an important component of unac-counted fishing mortality for several key NSW species.

Acknowledgements

This research was funded by the NSW Recreational FishingTrusts, NSW Department of Primary Industries and Southern CrossUniversity. M. Angle, C. Brand, M. Burns, N. Sarapuk, J. Crisp, B. Bur-ren and A. McManus are thanked for their technical contributions.

References

Arlinghaus, R., Cooke, S.J., Schwab, A., Cowx, I.G., 2007. Fish welfare: a challenge tothe feelings-based approach with implications for recreational fishing. Fish andFisheries 8, 57–71.

Bartholomew, A., Bohnsack, J.A., 2005. A review of catch-and-release angling mortal-ity with implications for no-take reserves. Reviews in Fish Biology and Fisheries15, 129–154.

Bellchambers, L.M., de Lestang, S., 2005. Selectivity of different gear types for samp-ling the blue swimmer crab, Portunus pelagicus L. Fisheries Research 73, 21–27.

Bellchambers, L.M., Smith, K.D., Evans, S.N., 2005. Effect of exposure to ice slurrieson nonovigerous and ovigerous blue swimmer crabs, Portunus pelagicus. Journalof Crustacean Biology 25, 274–278.

Boutson, A., Mahasawasde, C., Mahasawasde, S., Tunkijjanukij, S., Arimoto, T., 2009.Use of escape vents to improve size and species selectivity of collapsible pot forblue swimming crab Portunus pelagicus in Thailand. Fisheries Science 75, 25–33.

Broadhurst, M.K., Suuronen, P., Hulme, A., 2006a. Estimating collateral damage fromtowed fishing gear. Fish and Fisheries 7, 180–218.

Broadhurst, M.K., Dijkstra, K.K., Reid, D.D., Gray, C.A., 2006b. Utility of morphologicaldata for key fish species in southeastern Australian beach-seine and otter-trawlfisheries: predicting mesh size and configuration. New Zealand Journal of Marineand Freshwater Research 40, 259–272.

Broadhurst, M.K., Millar, R.B., Brand, C.P., 2009. Mitigating discard mortality fromdusky flathead Platycephalus fuscus gillnets. Diseases of Aquatic Organisms 85,157–166.

Butcher, P.A., Leland, J.C., Broadhurst, M.K., Paterson, B.D., Mayer, D.G., 2012. Giantmud crab (Scylla serrata): relative efficiencies of common baited traps andimpacts to discards. ICES Journal of Marine Science 69, 1511–1522.

Campbell, M.J., Sumpton, W.D., 2009. Ghost fishing in the pot fishery for blue swim-mer crabs Portunus pelagicus in Queensland, Australia. Fisheries Research 95,246–253.

Chang, E.S., 1995. Physiological and biochemical changes during the molt cycle indecapod crustaceans: an overview. Journal of Experimental Marine Biology andEcology 193, 1–4.

Dall, W., 1975. Indices of nutritional state in the western rock lobster Panuliruslongipes (Milne Edwards): II. Gastric fluid contents. Journal of ExperimentalMarine Biology and Ecology 18, 1–18.

Elwood, R.W., Barr, S., Patterson, L., 2009. Pain and stress in crustaceans? AppliedAnimal Behaviour Science 118, 128–136.

GenStat, 2010. GenStat for Windows, Release 12.2, 12th ed. VSN International Ltd.,Oxford.

Hay, T., Gribble, N., de Vries, C., Danaher, K., Dunning, M., Hearnden, M., Caley, P.,Wright, C., Brown, I., Bailey, S., Phelan, M., 2005. Methods for Monitoring theAbundance and Habitat of the Northern Australian mud Crab Scylla serrata. Fish-ery Report No. 80. Northern Territory Department of Business, Industry andResource Development, Darwin.

Henry, G.W., Lyle, J.M., 2003. The National Recreational and Indigenous Fishing Sur-vey. Australian Government Department of Agriculture, Fisheries and Forestry,Canberra, Australia, pp. 188.

ICES, 2005. Joint Report of the Study Group on Unaccounted Fishing Mortality(SGUFM) and the Workshop on Unaccounted Fishing Mortality (WKUFM), ICESCM 2005/B:08 , 25–27, September 2005. Aberdeen, UK, p. 68.

Johnson, D.D., Gray, C.A., Macbeth, W.G., 2010. Reproductive biology of Portunuspelagicus in a south-east Australian estuary. Journal of Crustacean Biology 30,200–205.

Jussila, J., McBride, S., Jago, J., Evans, L.H., 2001. Hemolymph clotting time as anindicator of stress in western rock lobster (Panulirus cygnus George). Aquaculture199, 185–193.

King, M., 2007. Fisheries Biology, Assessment and Management, 2nd ed. BlackwellPublishing Ltd., Oxford, pp. 382.

Lai, J.C.Y., Ng, P.K.L., Davie, J.F., 2010. A revision of the Portunus pelagicus (Linnaeus,1758) species complex (Crustacea Brachyura: Portunidae), with the recognitionof four species. The Raffles Bulletin of Zoology 58, 199–237.

Leavitt, D.F., Bayer, R.C., 1977. A refractometric method for determining serum pro-tein concentration in the American lobster. Aquaculture 12, 169–171.

Resea

L

M

M

P

P

P

P

P

P

S

Wasson, K., Lyon, B.E., Knope, M., 2002. Hair-trigger autotomy in porcelain crabs is

J.C. Leland et al. / Fisheries

eland, J.C., Butcher, P.A., Broadhurst, M.K., Paterson, B.D., Mayer, D.G., 2013. Damageand physiological stress to juvenile eastern rock lobster (Sagmariasus verreauxi)discarded after trapping and hand collection. Fisheries Research 137, 63–70.

cCullagh, P., Nelder, J.A., 1989. Generalized Linear Models, 2nd ed. Chapman andHall, London.

cPherson, R., 2002. Assessment of T bar anchor tags for marking the blue swimmercrab Portunus pelagicus (L.). Fisheries Research 54, 209–216.

arsons, D.M., Eggleston, D.B., 2005. Indirect effects of recreational fishing on behav-ior of the spiny lobster Panulirus argus. Marine Ecology Progress Series 303,235–244.

ascual, C., Sánchez, A., Sánchez, A., Vargas-Albores, F., LeMoullac, G., Rosas, C., 2003.Haemolymph metabolic variables and immune response in Litopenaeus setiferusadult males: the effect of an extreme temperature. Aquaculture 218, 637–650.

aterson, B., Mann, D., Kelly, B., Barchiesi, M., 2007. Limb-loss in pond-reared blueswimmer crabs Portunus pelagicus (L.): effect on growth in an indoor sheddingsystem. Aquaculture Research 38, 1569–1579.

erazzolo, L.M., Gargioni, R., Ogliari, P., Barracco, M.A.A., 2002. Evaluation of somehemato-immunological parameters in the shrimp Farfantepenaeus paulensissubmitted to environmental and physiological stress. Aquaculture 214, 19–33.

oole, S., Mayze, J., Exley, P., Paulo, C., 2008. Maximising the Revenue Within theNorthern Territory Mud Crab Fishery by Enhancing Post-Harvest Survival ofMud Crabs. Project Number 2003/240. Fisheries Research and DevelopmentCorporation and Department of Primary Industries and Fisheries, Queensland.

otter, I.C., de Lestang, S., 2000. Biology of the blue swimmer crab Portunus pelagicus

in Leschenault estuary and Koombana Bay, south-western Australia. Journal ofthe Royal Society of Western Australia 83, 443–458.

mith, L.D., Hines, A.H., 1991. Autotomy in blue crab (Callinectes sapidus) popula-tions: geographic temporal and ontogenetic variation. The Biological Bulletin180, 416–431.

rch 147 (2013) 304– 311 311

Smith, K.D., Hall, N.G., de Lestang, S., Potter, I.C., 2004. Potential bias in estimates ofthe size of maturity of crabs derived from trap samples. ICES Journal of MarineScience 61, 906–912.

Taylor, S., Landman, M.J., Ling, N., 2009. Flow cytometric characterization of fresh-water crayfish hemocytes for the examination of physiological status in wildand captive animals. Journal of Aquatic Animal Health 21, 195–203.

Uhlmann, S.S., Broadhurst, M.K., Paterson, B.D., Mayer, D.G., Butcher, P., Brand, C.P.,2009. Mortality and blood loss by blue swimmer crabs (Portunus pelagicus) aftersimulated capture and discarding from gillnets. ICES Journal of Marine Science66, 455–461.

Vazquez Archdale, M., Kariyazono, L., Anasco, C.P., 2006. The effect of two pot typeson entrance rate and entrance behaviour of the invasive Japanese swimmingcrab Charybdis japonica. Fisheries Research 77, 271–274.

Vazquez Archdale, M., Anasco, C.P., Kawamura, Y., Tomiki, S., 2007. Effect of twocollapsible pot designs on escape rate and behaviour of the invasive swim-ming crabs Charybdis japonica and Portunus pelagicus. Fisheries Research 85,202–209.

Wassenberg, T.J., Hill, B.J., 1989. The effect of trawling and subsequent handling onthe survival rates of the by-catch of prawn trawlers in Moreton Bay, Australia.Fisheries Research 7, 99–110.

Wassenberg, T.J., Hill, B.J., 1993. Selection of the appropriate duration of experimentsto measure the survival of animals discarded from trawlers. Fisheries Research17, 343–352.

a highly effective escape strategy. Behavioral Ecology 13, 481–486.Williams, M.J., Hill, B.J., 1982. Factors influencing pot catches and popula-

tion estimates of the portunid crab Scylla serrata. Marine Biology 71,187–192.