Species-specific at-vessel mortality of sharks and rays captured by demersal longlines

Unmanaged fishing mortality is considered the biggest threat to sharks and rays, which are commonly discarded after being captured in commercial and recreational fisheries directed at more economically valuable fishery resources. Quantifying mortality prior to release (referred to as ‘at vessel mortality’, AVM) improves our understanding of the total mortality of sharks and rays. In this study, the effects of body size, sex, soak time, bottom depth and latitude on AVM were evaluated on a range of shark and ray species captured by demersal longlines off the coast of Western Australia. Our study provides new evidence for species not previously studied of the importance of deriving species-specific AVM as species was by far the most important predictor of AVM. Some species were inherently more susceptible to gear interactions than other species. Therefore, the probability of a species surviving the interaction with a fishing gear must be taken into consideration when making management recommendations because total mortality may be much greater than that estimated from retained catches only.