Effect of a precautionary management measure on the vulnerability and ecological risk of elasmobranchs captured as target fisheries

Abstract

The impact of fisheries on elasmobranch populations has been widely documented; however, baseline information on shark and batoid management remains limited, particularly in tropical areas and in developing countries. The use of precautionary measures and data-poor methods have been recommended as valuable tools to guide the management and conservation of marine taxa when information is scarce and the effect of fisheries on populations is evident. A Productivity Susceptibility Analysis (PSA) and intrinsic rebound potential (r) estimates were used to evaluate the vulnerability and resilience of elasmobranchs before and after a precautionary measure (closure of the fishery) was implemented in the Archipelago of San Andrés, Providencia and Santa Catalina, Colombia (Seaflower Biosphere Reserve). We identified locally large information gaps, specifically on the demographic and life history parameters of the 15 elasmobranch species (13 sharks and 2 rays) evaluated for the Archipelago. Including fishing effects, nine large commercial shark species were identified as the most vulnerable and with the lowest intrinsic rebound potential, while the least vulnerable species was the whale shark (Rhincodon typus), which presented the third highest value of r2M. Once the fishery was closed, the vulnerability of large sharks decreased greatly. Our findings highlight the importance of: involving communities to achieve effective management processes; implementing precautionary measures for high impact and targeted fisheries; and using valuable data-poor tools for the study of populations as an alternative for evaluating and suggesting management measures. Finally, based in PSA and intrinsic rebound potential results, it is suggested to maintain the fishing ban in consensus with the fishermen, and to evaluate economic alternatives already being generated in the area such as recreational diving and ecological tourism, among others.