Abstract
Traditional single-species fisheries management does not explicitly account for multispecies interactions and has not always performed well for avoiding overfishing or rebuilding many fisheries. Considering these interactions has become increasingly important for effectively managing mixed-species fisheries. Ecosystem-based fisheries management (EBFM) is a more holistic option which considers the biological, physical, and socioeconomic factors influencing stocks and requires new tactics that can be informed by interdisciplinary research. One such approach builds off of portfolio optimization used in the finance field to manage the risk of achieving a target reward through the formation of investment portfolios whereby the constituent assets are selected based on their temporal covariance. A fisheries portfolio involves jointly managing fish stocks that have shared ecological, technical, market, or regulatory interactions. In New England, fishers capture demersal finfish alongside other demersal species resulting in mixed species catches, but these species are currently assessed and managed independently. Here, we examine a candidate portfolio comprising New England demersal finfish with shared technical interactions resulting in mixed species catch, using historical landings and revenue data (1981–2021). Analysis of efficient frontiers indicated that most target revenues could have been achieved with less risk (i.e. of not achieving the target revenue) had a portfolio approach to management been used for these species. Additionally, the sensitivity of this candidate multispecies fishery portfolio to two prominent data decisions was examined, and it was found that risk estimates were sensitive to both the exclusion of species from the initial candidate portfolio and the length of the time series analyzed. Examination of the changes in the frontiers for three periods of the time series characterized by shifts in management regime for this fishery showed that a portfolio approach could improve performance for fisheries utilizing either input or output control systems. These results suggest that portfolio approaches may provide a useful framework for evaluating revenue-risk tradeoffs in multispecies fisheries and represent a potential tool to support EBFM.