Shark Catch in Pelagic Longline Fisheries: A Review of Mitigation Measures

Pelagic longline gear is used throughout the world’s oceans to capture tuna and tuna-like species. Longline gear is typically deployed from a single vessel across many miles of ocean. The vessel deploys a single mainline that is periodically buoyed with floatation devices and thinner branchlines (with baited hooks) are then attached to the mainline between the floats (Fig. 1 – Beverly et al. 2009). Within this simple framework, a variety of configurations and operational practices can be employed to specifically target different depths and species of fish (Beverly et al. 2003). Although some longline fisheries capture sharks as commercially viable target species or as low- value incidental catch, the purpose of this review is to summarize studies that have viewed shark capture as unwanted bycatch (i.e., discards). This paper also reviews methods aimed to mitigate catch rates and post release mortality of sharks in fisheries that target tuna and tuna-like species. Some of the research is on a single species, but most is on several of the most commonly encountered species or on species complexes.