Simulating effects of hook-size regulations on recreational harvest efficiency in the northern Gulf of Mexico red snapper fishery

•Imposing domed contact selectivity with peak at small size improved model fit.•Shifting selectivity to larger sizes reduced discards and increased retained catch.•Empirical data suggest increasing contact selectivity with larger hooks is plausible.•Impacts of hook size regulations dependent upon fisher retention behavior. Recreational fishers discard millions of red snapper (Lutjanus campechanus) annually in the northern Gulf of Mexico (nGOM), resulting in significant foregone yield. We conducted simulation modeling to evaluate the potential for hook-size regulations to improve efficiency in the recreational red snapper fishery. First, we imposed a suite of candidate parameter sets, informed by recent empirical studies, within the 2015 red snapper assessment model to estimate contact-selectivity of recreational fleets in the northeastern or northwestern GOM. We then evaluated potential hook-size regulations by imposing a suite of candidate parameter sets on future contact-selectivity of each recreational fleet, conditional on likelihood-based estimates from the first simulation exercise. In the assessment model, maximum likelihood values improved when strongly domed contact-selectivity curves with peak size approximating the current minimum length limit were imposed in either the eastern or western recreational fleet. Simulation results indicate mandating large hook sizes could modestly increase retained catch for the eastern recreational fleet while dramatically reducing the number of red snapper discarded by either fleet. Realized benefits of hook-size regulations will depend upon future fisher retention behavior, such as the intensity of live high-grading, discard mortality reduction practices, such as venting and the use of descender devices, and changes to current management regulations.