Shark bycatch and post-release survival
Shark populations are in decline in every ocean, mostly due to overfishing (Worm et al., 2013; Dulvy et al., 2014). There is now increased attention on shark-fishery interactions and the effects such interactions are having on shark populations.
Researchers are conducting several studies to investigate the post release mortality rates that incidental sharks may suffer. Specifically, scientists are now looking at the degree of physiological disruption in blood chemistry and validating whether or not an animal survived the fishing interaction through the use of Pop-up Satellite Archival Tags (PSATs). Several studies have shown that certain blood chemistry parameters – elevated lactate, adrenaline, glucose levels, and low pH, for example – correlate to mortality in many shark species. Additionally, these studies are also finding that responses to the stress of capture are species specific. Many of the deep diving, wide ranging, faster swimming shark species with higher metabolic demands, such as hammerhead and thresher sharks, exhibit higher post release mortality rates than slower, coastal species such sandbar and tiger sharks (Heberer et al. 2009; Marshall et al. 2012; Gallagher et al. 2014). These results have major implications for stock assessments and fishery management plans.