Modeling temporal closures in a multispecies recreational fishery reveals tradeoffs associated with species seasonality and angler effort dynamics

Abstract

Seasonal closures are commonly used to reduce fishing mortality in recreational and commercial fisheries, but they may be less effective when effort is merely displaced to the open season or in multispecies fisheries that allow for discarding to continue while other species are targeted. The latter is especially true for the valuable multispecies recreational reef fish fishery in the Gulf of Mexico, where discard mortality is high and it can be difficult to avoid catching one species while fishing for others. We evaluated the utility of complete bottom fishing closures (in addition to already mandated harvest closures) that would temporarily prohibit recreational reef fishing as a means to control effort, reduce the amount of dead discards, and improve stock status of multiple species. In this study we developed age-structured population models for six Gulf of Mexico reef fish species that dominate the recreational catch, with each model linked to a monthly effort dynamic model for the recreational fishery. The effect of closing any given month(s) varied across species and resulted in tradeoffs, such that some closures may result in positive effects on biomass of one species and negative effects on others. For example, a spring closure was predicted to have positive effects on Red Snapper Lutjanus campechanus spawning stock biomass but negative effects on Gag grouper Mycteroperca microlepis due to the contrasting patterns in harvest rates during those months. These tradeoffs were associated with seasonal availability patterns and the degree to which anglers might shift effort to the open season. The closure scenarios that were most likely to reduce dead discards without negatively impacting harvest, spawning biomass, or total effort occurred in late winter and early spring (March & April). In evaluating seasonal fishing closures, the gains in biomass and reductions in dead discards must be weighed against the socio-economic tradeoffs, in terms of lost effort-generated revenue at various spatial and temporal scales and angler dissatisfaction.