What is multispecies MSY? A worked example from the North Sea

Area of Science:

• Fisheries Science
• Ecosystem Management
• Conservation Biology

Background:

• Maximum Sustainable Yield (MSY) is a long-standing fisheries management goal, established in the 1930s and legally mandated.
• Applying MSY to single stocks in stable environments is straightforward, but problematic in mixed, multispecies fisheries with complex interactions.

Purpose of the Study:

• To introduce a novel framework for evaluating multispecies MSY.
• To assess the performance of simple harvest control rules in multispecies fisheries management.
• To compare these rules against scenarios using stock-specific fishing mortality rates.

Main Methods:

• Developed a framework integrating stock depletion risk and expected long-term yield for multispecies MSY.
• Evaluated simple harvest control rules using a common fishing mortality rate (F) and target biomass fraction.
• Employed multispecies management strategy evaluation to compare rule performance against stock-specific F scenarios.

Main Results:

• The proposed simple framework yielded outcomes comparable to more complex, stock-specific fishing mortality rate estimates.
• Simple harvest control rules, when applied consistently, can achieve results similar to sophisticated assessments.

Conclusions:

• Effective multispecies MSY management may rely more on setting appropriate biomass targets and consistently applying harvest control rules.
• Prioritizing robust biomass targets and adherence to control rules could be more critical than precisely calculating individual stock fishing mortality rates.