The physiological effects of capture stress, recovery, and post-release survivorship of juvenile sand tigers (Carcharias taurus) caught on rod and reel

Abstract

Current shark fishery management regulations in the US Atlantic, as well as other regions worldwide, mandate the release of sand tigers (Carcharias taurus) captured in recreational fisheries. To examine the efficacy of this strategy as a conservation tool, the physical and physiological effects of capture stress and post-release survivorship were examined in juvenile sand tigers angled on conventional rod and reel tackle with offset circle hooks. Analysis of blood samples obtained immediately after capture (n=84) indicated that, relative to minimally stressed captive individuals, juvenile sand tiger blood biochemistry is disturbed after brief (<7min) angling events. Serial blood sampling of five captive sharks subjected to a 3min simulated rod and reel angling event revealed rapid and significant disruptions in blood biochemistry with physiological recovery within 12–24h. Post-release monitoring of 65 sharks surgically implanted with acoustic tags demonstrated high degrees of immediate (99%), short- (82%), and long-term post-release survivorship (75%). Physiological disruptions did not appear to reduce immediate survivorship (5 days post capture), however, sharks hooked internally had lower rates of survival 50–100 days following release. Overall, these results suggest that juvenile sand tigers are able to cope with and survive the physiological stress associated with brief rod and reel capture, but physical trauma associated with hook location can impair post-release survival. Regardless, mandatory release appears to be a viable management strategy for juvenile sand tigers captured in rod and reel fisheries.