Testing of hook sizes and appendages to reduce yelloweye rockfish bycatch in a Pacific halibut longline fishery

Abstract

In Pacific halibut (Hippoglossus stenolepis) longline fisheries in the eastern North Pacific Ocean bycatch of yelloweye rockfish (Sebastes ruberrimus) is a concern as their stock status along the U.S. West Coast is “rebuilding” from being “overfished”, the southeast Alaska stock has shown a ∼60% decline since at least 1994 and through 2015 where it stabilized, and the Canadian stock has been recently declared “threatened”. In this study, we evaluated how size 16/0 and 18/0 circle hooks affect the catch efficiency of Pacific halibut and yelloweye rockfish. Further, we examined the catch efficiency of these hooks modified with a 3.1 mm stainless-steel wire appendage extending 7.6 cm from their shank at either a 45° or 90° angle. We estimated hooking location probabilities for Pacific halibut and yelloweye rockfish for the hooks tested, and tested for a difference in the time of capture between Pacific halibut and yelloweye rockfish. Results showed that hook size did not significantly affect the catch efficiency of Pacific halibut or yelloweye rockfish. However, hooks with a 45° appendage angle caught significantly fewer yelloweye rockfish than hooks without an appendage, irrespective of hook size. Appendage angle did not affect the catch efficiency of Pacific halibut. For both Pacific halibut and yelloweye rockfish, the most frequent hooking location was hook through cheek, both with and without an appendage. Time of capture of Pacific halibut and yelloweye rockfish did not differ over the duration of a set; however, the majority (75%) of individuals were caught within 2.5 h of gear deployment. Results from our study suggest that hook appendages could have potential use in reducing catch rates on yelloweye rockfish in Pacific halibut longline fisheries, which could lead to increased fishing opportunities, more efficient Pacific halibut fisheries and less effect of fluctuations in the more productive Pacific halibut stock on fisheries that may be constrained by yelloweye rockfish.