Abstract
The shortfin mako shark (Isurus oxyrinchus) is a species commonly targeted by commercial and recreational anglers in many parts of the developed world. In Australia, the species is targeted by recreational anglers only, under the assumption that most of the sharks are released and populations remain minimally impacted. If released sharks do not survive, the current management strategy will need to be revised. Shortfin mako sharks are commonly subjected to lengthy angling events; however, their endothermic physiology may provide an advantage over ectothermic fishes when recovering from exercise. This study assessed the post-release survival of recreationally caught shortfin mako sharks using Survivorship Pop-up Archival Transmitting (sPAT) tags and examined physiological indicators of capture stress from blood samples as well as any injuries that may be caused by hook selection. Survival estimates were based on 30 shortfin mako sharks captured off the south-eastern coast of Australia. Three mortalities were observed over the duration of the study, yielding an overall survival rate of 90%. All mortalities occurred in sharks angled for <30 min. Sharks experienced increasing plasma lactate with longer fight times and higher sea surface temperatures (SSTs), increased plasma glucose at higher SSTs and depressed expression of heat shock protein 70 and β-hydroxybutyrate at higher SSTs. Long fight times did not impact survival. Circle hooks significantly reduced foul hooking when compared with J hooks. Under the conditions of this study, we found that physical injury associated with hook choice is likely to have contributed to an increased likelihood of mortality, whereas the high aerobic scope associated with the species' endothermy probably enabled it to cope with long fight times and the associated physiological responses to capture.
Highlights
IntroductionRecreational fishing is a popular pastime in many parts of the developed world (Post et al, 2002) and, while the negative impacts of fishing on global populations have typically been attributed to commercial fisheries, it is becoming more commonly accepted that the recreational sector contributes to many of these impacts (McPhee et al, 2002; Post et al, 2002; Coleman et al, 2004; Cooke and Cowx, 2004; Arlinghaus et al, 2005; Lewin et al, 2006)
Fight time did not impact shortfin mako shark survival, despite elevated plasma La− and plasma Na+ after long fight times, indicating pronounced metabolic acidosis. This highlights the resilience of this species to capture stress and is likely to reflect the aerobic capabilities associated with endothermy
Fight times reported in the present study represent those that would be imposed by recreational fishers and give merit to the use of catch-and-release fishing as a conservation method for shortfin mako
Summary
Recreational fishing is a popular pastime in many parts of the developed world (Post et al, 2002) and, while the negative impacts of fishing on global populations have typically been attributed to commercial fisheries, it is becoming more commonly accepted that the recreational sector contributes to many of these impacts (McPhee et al, 2002; Post et al, 2002; Coleman et al, 2004; Cooke and Cowx, 2004; Arlinghaus et al, 2005; Lewin et al, 2006). The shortfin mako shark (Isurus oxyrinchus) is vulnerable to fishing pressure because of its lifehistory characteristics (Hoenig and Gruber, 1990; Stevens, 2008; Semba et al, 2011). It is an endothermic species, with one of the highest metabolic rates recorded for any pelagic shark; this implies a high aerobic scope that could be an advantage when dealing with physiological disturbances (Sepulveda et al, 2007). There is, little information on postrelease survival rates for recreationally caught shortfin mako sharks, and uncertainty as to the efficacy of the current management strategy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
