Impacts of hook size on catch and bycatch in the eastern Gulf of Mexico reef fish fishery using electronic monitoring

Objective To evaluate the impacts of hook size on catch and discards of reef fish using an electronic monitoring video platform in collaboration with two commercial bottom longline vessels in the eastern Gulf of Mexico. Methods Vessels deployed a standard hook size commonly used in the fishery (13/0) for comparison with a larger version (15/0) during 16 fishing trips conducted between April 2022 and January 2023. Results The study successfully documented hook-specific attributes, including hook size and location, and used hook counts to generate projected discard and retention rates. Red Grouper Epinephelus morio, the primary target in this fishery, showed a reduction in projected discards with the use of 15/0 hooks, being 38% lower on average when compared with 13/0 hooks. An average decrease in discards of 21 undersized Red Grouper per haul and an average loss of six legally retainable Red Grouper per haul was projected while using 15/0 hooks. Catch rates for Red Snapper Lutjanus campechanus were lower with 15/0 hooks, which was also evident in other important reef fish species, such as Yellowedge Grouper Hyporthodus flavolimbatus, Tilefish Lopholatilus chamaeleonticeps, Blueline Tilefish Caulolatilus microps, Gray Snapper Lutjanus griseus, Lane Snapper L. synagris, and Red Porgy Pagrus pagrus. Conclusions In multispecies fisheries with elevated discard rates and associated mortality, gear modifications that reduce bycatch can enhance sustainability and support increases in allowable harvest. However, potential trade-offs, including reduced catch of some economically valuable targeted species, must be carefully evaluated. The application of electronic monitoring in this study proved to be an effective tool for capturing detailed gear-specific data, allowing for species-specific discard rates and impacts to be evaluated in a timely and efficient manner.