Comparability of blue shark mortality estimates for the Atlantic and Pacific longline fisheries

Abstract

Blue sharks Prionace glauca are among the most frequently caught and discarded fish species in pelagic longline fisheries of both the Atlantic and Pacific oceans. Fishery-specific differ- ences between Atlantic and Pacific longliners lead to differences in both hooking and post-release mortality rates. However, the estimates of both hooking and post-release mortality reported by Moyes et al. (2006; Trans Am Fish Soc 135:1389-1397) around Hawaii are considerably lower than those reported elsewhere, both in the Atlantic and the Pacific. Our comparison of Campana et al. (2009; Mar Ecol Prog Ser 387:241-253) with Moyes et al. suggests that the difference in blue shark mortality estimates is explained by the partial use of J hooks in the Atlantic fishery, and by the shorter soak time, fewer hooks fished, and gentler handling practices by the scientific crew in the Pacific study by Moyes et al. The study by Moyes et al. is an important contribution to our understanding of blue shark mortality; nevertheless, we consider it inappropriate to use their low estimates of blue shark mortality as a proxy for bycatch mortality rates in the commercial fishery.