A fisheries management strategy robust to ignorance: rotational harvest in the presence of indirect fishing mortality

Abstract

We develop a simple theoretical model of yield and spawning stock biomass per recruit for the American sea scallop (Placopecten magellanicus), which appears to have high indirect fishing mortality when harvested with dredges, i.e., mortality caused by the act of fishing that does not result in landings. The age at and degree to which individuals are affected by the indirect mortality are unknown, and it does not appear possible to develop a robust harvest strategy with yearly harvests unless indirect fishing mortality is well quantified. We show that there could be substantial benefits to a rotational harvest strategy for sessile species with high indirect fishing mortality. First, the strategy appears to be robust to ignorance about indirect fishing mortality and results in equal or better yields than a yearly harvest across a wide range of indirect fishing mortalities. Second, under most conditions, a higher spawning stock biomass is maintained. Third, rotational management is more easily enforced, as it does not require specifying a narrow range of fishing mortality in order to maximize yield.