Exploring benefits of spatial cooperative harvesting in a sea urchin fishery: an agent‐based approach

Abstract

Abstract Sedentary or low‐mobility organisms show a high degree of dependency with their substrate, where its heterogeneity often determines small‐scale spatial patterns of distribution, life history traits, and fishery yields. For sea urchins, this spatial structure is usually shaped by food availability, habitat structure, individual movement, and fishery dynamics. All of these have a significant impact on their physiological and reproductive status and in particular on their gonadal content. These patterns are of particular interest considering that the sea urchin fishery is a roe fishery where marketability depends on gonad yield and quality, which in turn is related to spatial and temporal variations in associated kelp beds. Thus, better gonad quality and yields generate higher profits for both fishers (divers) and processors. However, competition among divers within a non‐cooperative system creates a “race for shellfish” precluding higher gonad yields per unit of effort. A spatially explicit agent‐based model for the San Diego, California red sea urchin (Strongylocentrotus franciscanus) fishery was developed in order to assess the benefits of cooperative harvesting by depicting spatial and temporal variations in fishery yields. A cooperative harvesting scenario where divers consistently target those areas with higher yields avoiding low‐quality sea urchins was compared against a non‐cooperative situation where divers harvest at random or based only on densities of sea urchins. Sea urchin population at the end of the simulation period was 20% higher for the most cooperative scenario compared to the non‐cooperative fishery. Further, for the most cooperative scenario where information sharing among divers is greatest and harvest is coordinated, sea urchin catches were at least 10% higher and gonad yield 35% higher than in the non‐cooperative scenario. In this model, information sharing and organized harvesting typical of well‐functioning cooperatives allowed fishers to optimize the use of the resource in terms of higher gonad yields per unit of effort while maintaining the productivity of the stock. This study also highlights the importance of community‐based management (i.e., collaborative efforts in assessment, management, and governance of fisheries between fishers, scientists, and managers) toward improving fisheries sustainability.

Keywords

• community‐based management
• cooperative harvesting
• sea urchins: individual‐based models
• small‐scale fisheries
• spatially explicit modeling