The effect of hook appendage length on species' catch probability in a Pacific halibut longline fishery

In Pacific halibut ( Hippoglossus stenolepis ) longline fisheries from southeast Alaska to the United States West Coast, restrictive harvest limits have been placed on yelloweye rockfish ( Sebastes ruberrimus ) due to low spawning biomass levels. We compared the catch probability of Pacific halibut and yelloweye rockfish between three appendage (app.) hook designs and a standard hook design. Specifically, we tested a hook design with a stiff app. bar (3.1 mm diameter) that extended outward from its shank at a 45° angle on the non-offset side at a length of either 3.8, 7.6, or 11.4 cm. We also used hook timers on a subset of hooks to examine species' time of capture, estimated hooking location probabilities, and species dominance. Compared directly to the standard hook, the 3.8 cm and 7.6 cm app. hooks did not reduce Pacific halibut catches while significantly reducing yelloweye rockfish catches by an average of 28% and 45%, respectively. For Pacific halibut and yelloweye rockfish, the most frequent hooking locations were hook-through-cheek and hook-through-jaw. For each hook type, yelloweye rockfish followed by Pacific halibut were the most dominant species caught. In terms of time of capture, most fish were caught within 2 h of the gear being deployed. These findings suggest that hook appendages have potential to reduce yelloweye rockfish bycatch in Pacific halibut fisheries and that reducing soak durations could potentially improve fishers' catch efficiency.