A comparison of catch efficiency and bycatch reduction of tuna pole-and-line fisheries using Japan tuna hook (JT-hook) and circle-shaped hook (C-hook)

Abstract

Unwanted bycatch of sea turtles in the tuna fisheries is a global challenge. To evaluate whether the incidental catch of sea turtles could be reduced through changes in fishing gear, this study compared catch rates and bycatch in the tuna pole-and-line with the addition of above-water lights (PL) fisheries using a Japan tuna hook (JT-hook) and a circle-shaped hook (C-hook). There were two phases to this study. First, five PL fishing vessels that used traditional JT-hooks were compared with five PL fishing vessels that used circle-shaped hooks throughout 1 full year of fishing. Results showed that C-hooks significantly reduced bycatch of sea turtle, while negligibly increasing the catch of yellowfin (Thunnus albacares) and bigeye (Thunnus obesus) tuna. Second, we conducted the onboard research to investigate the effect of JT-hook v. C-hook on the catch rates of commercial PL fishery. Results showed that there were higher catch rates of long snouted lancefish (Alepisaurus ferox) and wahoo (Acanthocybium solandri), but lower catches of thresher shark (Alopias spp.) on C-hooks, with no significant differences for other species considered. Our results suggest that the use of C-hooks in the PL fishery is beneficial to protected endangered sea turtle species.