Effects of unregulated international fishing on recovery potential of the sandbar shark within the southeastern United States

Abstract

Coastal sharks are challenging to manage in the United States due to their slow life history, limited data availability, history of overexploitation, and competing stakeholder interests. Furthermore, species like the sandbar shark ( Carcharhinus plumbeus) are subjected to international exploitation unmanaged by the US. We conducted a management strategy evaluation using Stock Synthesis on the sandbar shark to test the performance of various configurations of a threshold harvest control rule. In addition to uncertainties addressed in the operating model (OM), we built multiple implementation models to address uncertainties related to future levels of a partially unmanaged source of removals, the combined Mexican and US recreational (MexRec) fleet. We found that the presence of unregulated removals had the potential to significantly influence the success of the various management procedures (MPs) tested. Notably, if MexRec catches continue to increase with total stock abundance following historical trends, the rate of MexRec removals will be too large to allow the sandbar shark to recover across OMs. We present trade-offs between performance metrics across a range of 24 MPs and three implementation models.