Assessing shark bycatch condition and the effects of discard practices in the Hawaii-permitted tuna longline fishery

The incidental capture of sharks in commercial fisheries targeting tuna and billfish is having a negative impact on pelagic shark populations. Recently, studies have shown that some shark species captured in longline and purse seine fisheries may sustain high levels of post-release mortality due to injuries resulting from the fishing interaction. Researchers have identified the three main factors that lead to mortality in sharks; 1) the physiology of the species where some are more susceptible to the lethal effects of stress, 2) the duration of the interaction, and 3) the methods used to release the animal. In this study and in collaboration with the Pacific Islands Regional Observer Program (PIROP), we are assessing the handling and discard practices used in the Hawaii and American Samoa-permitted tuna longline fisheries and their effects on the release condition and survivability of sharks with newly established condition criteria and handling codes that are recorded by at-sea observers. Post-release survival rates are estimated through the use of pop-off archival satellite tags (SPAT, Wildlife Computers Inc.). PIROP observers were trained in the use of the new shark-focused condition and handling codes and on methods of deploying satellite tags on sharks over the rail of longline vessels while the sharks are in the water and prior to discard. In this way we will quantitatively assess total fishery mortality and identify the best handling practices for maximizing post-release survival for sharks discarded at sea.