Challenges of management strategy evaluation for small pelagic fish: the Bay of Biscay anchovy case study

Abstract

Modeling major uncertainties in population and fishery dynamics is fundamental for reliable management strategy evaluation. Here we describe the bio-economic impact assessment of alternative harvest control rules (HCRs) in developing a management plan for Bay of Biscay anchovy, using R software and the FLBEIA software package. Further, we show how the modeling work was adapted as new biological information and data sources became available. The underlying general HCR consists of exploiting a proportion of the estimated spawning stock biomass (SSB), and is operative for 2 alternative management calendars: July-June or January-December. The final shape of the rule is determined by the harvest rate, the biomass trigger points, and the total allowable catch (TAC) thresholds. The performance of the HCRs was evaluated according to the biological and economic risks, probability of fishery closure, expected average catches, and their standard deviation. Robustness of these rules, given alternative recruitment models and quota shares among fleets, was also tested. The inclusion of a recruitment index allowed moving the management calendar from July-June to January-December, and led to higher (similar to 15 \%) and more stable average catches, while reducing biological risks and the probability of fishery closure (by similar to 25 \%). The presence of minimum and maximum TAC levels allowed improved fishery performance. Recruitment was the uncertainty of major relevance in determining the relative performance of the rules, while there was little effect on biological risk of different quota shares among countries. The simulation results were the cornerstone for the selection of the adopted HCRs by stakeholders and managers.