Applying tree analysis to assess combinations of Ecosystem-Based Fisheries Management actions in Management Strategy Evaluation

Abstract

There is growing need to evaluate the performance of possible Ecosystem-Based Fisheries Management (EBFM) procedures to develop feasible operational alternatives to single species management. We used Management Strategy Evaluation (MSE) to examine consequences of implementing combinations of three EBFM actions and used tree analysis to assess drivers of management performance. We used a multi-species production model, characteristic of the commercial finfish fishery on Georges Bank, USA, and included observation error when assessing stock and ecosystem status. Combinations of catch ceilings that limited total system removals, indicator-based harvest control rules that adjusted fishing at the aggregate or ecosystem level, and precautionary single-species fishing mortality rates were implemented in tandem over a thirty-year projection period. Statistical tree analysis identified EBFM procedures capable of meeting combinations of catch, biomass, biodiversity, and economic goals, but we found catch ceilings tended to mask the impact of other EBFM actions. It was necessary to implement two or more EBFM actions combining broad-scale limitations on removals with management actions targeting vulnerable ecosystem components to address trade-offs between potentially conflicting management objectives.