HOW MODIFIED TROPHIC INTERACTIONS CREATE SOCIO-ECOLOGICAL TRADEOFFS: A CASE STUDY OF NARRAGANSETT BAY FISHERIES

Abstract

Marine fisheries represent a social-ecological system driven by both complex ecological processes and human interactions. Fisheries management requires an understanding of both the biological and social components, and management failure can occur when either are excluded. Despite the significance of both, most research has focused on characterizing biological uncertainty rather than on better understanding the impacts of human behavior. In this study, we use the fisheries in Narragansett Bay (Rhode Island, USA) as a case study to understand how fisher behavior influences food web dynamics. Narragansett Bay holds both a commercial fishery for forage fish (i.e. menhaden) and a recreational fishery for their predators (i.e. striped bass, bluefish). To explore tradeoffs that might exist between these two fisheries, we coupled a food-web model to a recreational fishers’ behavior model, creating a dynamic social-ecological representation of the ecosystem. Fish biomass was projected until 2030 in both the stand-alone food web model and the coupled social-ecological model, with results highlighting how the incorporation of fisher behavior in modeling can lead to changes in the projected ecosystem. We tested model sensitivity to three attributes: 1) the forage fish commercial harvest scenario, 2) the predatory (“piscivorous”) fish abundance-catch relationship in the recreational fishery, and 3) the rate at which recreational fishers become discouraged (termed “satisfaction loss”). Higher commercial harvest of forage fish led to significantly lower piscivorous fish biomass but had minimal effects on the number of piscivorous fish caught recreationally or recreational fisher satisfaction. Both the abundance-catch relationship and satisfaction loss rate had effects on the fish biomass, the number of fish caught recreationally, and recreational fisher satisfaction. The number of piscivorous fish caught recreationally and recreational fisher satisfaction were positively correlated, but neither one was positively correlated with piscivorous fish biomass. Our results highlight that fisher behavior can significantly influence food web dynamics, including fish biomass and the number of fish caught. Social responses to changing ecosystems should be explicitly incorporated into ecosystem modeling to improve ecosystem-based management efforts. The methods we used to link the food web and fisher behavior models provide a framework of how human behavior can be incorporated into social-ecological modeling.