Fisheries Research 147 (2013) 304–311 Contents lists available at ScienceDirect Fisheries Research jou rn al hom ep age: www.elsevier.com/locate/fishres Relative trap efficiency for recreationally caught eastern Australian blue swimmer crab (Portunus pelagicus) and associated injury and mortality of discards Jesse C. Leland a,b,∗ , Paul A. Butcher a , Matt K. Broadhurst a , Brian D. Paterson c , David G. Mayer d a New South Wales Department of Primary Industries, Fisheries Conservation Technology Unit, National Marine Science Centre, P.O. Box 4321, Coffs Harbour, NSW 2450, Australia b Marine Ecology Research Centre and National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Lismore, NSW 2480, Australia c Department of Agriculture, Fisheries and Forestry, Bribie Island Research Centre, P.O. Box 2066, Woorim, QLD 4507, Australia d Department of Agriculture, Fisheries and Forestry, Ecosciences Precinct, GPO Box 267, Brisbane 4001, Australia a r t i c l e i n f o Article history: Received 12 October 2012 Received in revised form 18 June 2013 Accepted 11 July 2013 Keywords: Discarding Relative efficiency Portunus pelagicus Trap Unaccounted fishing mortality a b s t r a c t Australian recreational fishers targeting Portunus pelagicus are regulated by unverified gear restrictions which, combined with size, sex and quota regulations, result in >40% of their catches being discarded; all with 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 subsequent injury, physiological stress and mortality (in cages with controls over three days) of discarded P. pelagi- 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 and teleost bycatch. Five percent of individuals lost 1–3 appendages, usually during disentanglement, and only 1.1% of discarded P. pelagicus died (all within 24 h). Haemolymph parameters were mostly affected by 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. © 2013 Elsevier B.V. All rights reserved. 1. Introduction For many exploited aquatic species, unaccounted fishing mor- tality can represent a substantial component of their total fishing mortality and so accurate estimation is essential for effective stock management (ICES, 2005; King, 2007). More than six sub-components of unaccounted fishing mortality have been recognised. However, most attention has focused on the mortal- ity caused during discarding (or “release”); not only because such estimates often are the easiest to acquire, but also because gen- erally they are assumed to comprise the greatest proportion of unaccounted deaths (Broadhurst et al., 2006a). Among recreational fisheries, most discard mortality studies have involved teleosts, reflecting not only concerns about effort and subsequent stock sustainability, but also the welfare of survivors ∗ Corresponding author at: Marine Ecology Research Centre, School of Environ- ment, Science and Engineering, Southern Cross University, P.O. Box 157, Lismore, NSW 2480, Australia. Tel.: +61 2 6620 3786; fax: +61 2 6621 2669. E-mail address: jesse.leland@scu.edu.au (J.C. Leland). (Bartholomew and Bohnsack, 2005; Arlinghaus et al., 2007). Until recently, much less attention had been directed towards assessing the fate of recreationally discarded crustaceans (Parsons and Eggleston, 2005; Butcher et al., 2012; Leland et al., 2013); perhaps owing to their relatively greater resilience to associated stressors (Wassenberg and Hill, 1993) and/or their perceived inability to feel pain (Elwood et al., 2009). Like teleosts, crustacean discard mortality can be directly esti- mated over the short term (Wassenberg and Hill, 1993; Broadhurst et al., 2009), although finer-scale analyses of physiological impacts are 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 internal homeostasis (Poole et al., 2008; Uhlmann et al., 2009), which often correlate with discard-related stressors (e.g. air exposure and appendage loss) that can alter immunocompetence. Deviation from normal 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 0165-7836/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fishres.2013.07.006