Meeting Abstract
59.8 Sunday, Jan. 5 15:15 Evolutionary traits explain the vulnerability of apex predatory sharks to human-induced environmental changes GALLAGHER, A/J*; ORBESEN, E/S; HAMMERSCHLAG, N; SERAFY, J/E; University of Miami, Florida USA; National Marine Fisheries Service, NOAA; University of Miami, Florida, USA; National Marine Fisheries Service, NOAA agallagher@rsmas.miami.edu
Understanding how species respond to and cope with novel conditions is becoming increasingly important for predicting how their populations are affected by environmental impacts and stressors. Since no two species are affected the same way, a continuum of sensitivity or resilience often emerges, which may be useful for identifying which species may be especially at risk. We examined the survival of 12 pelagic shark species encountered in as bycatch in a pelagic longline fishery in relation to fishery target and other operational, environmental, and biological variables. Survival estimates ranged from 33% (night shark) to 97% (tiger shark) with eight of the 12 species examined being significantly affected by at least one of the examined variables. We placed our survival results within a risk assessment framework that incorporated species-specific reproductive potential (age at maturity and fecundity) in order to generate an index of species susceptibility. The bigeye thresher, dusky shark, night shark, and scalloped hammerhead exhibited the highest vulnerabilities to bycatch mortality. We discuss our results in terms of the evolutionary history of closely related species and use morphological and physiological traits to suggest that specialized species appear to be the most threatened (i.e., the crash test hypothesis). This study suggests that the evolutionary history and biological traits of species, in addition to survival rates and life-history parameters, may be useful to consider in conservation planning, and techniques that avoid fisheries interactions in the first place may be the best strategy for mitigating bycatch mortality for highly vulnerable species.
