From numbers to decision spaces: boosting the Management Strategy Evaluation tool through interdisciplinary approaches

Increased complexity, uncertainty, and changing patterns are trapping scientists and policy-makers in a dilemma: how to advise for sustainable fisheries management. Conventional approaches have proven unfit when considering fisheries as social-ecological systems, creating unbalances across the environmental, economic and social dimensions. While the clamour for integrated advice is unanimous, and the scientific community has provided robust frameworks, their application in actual decision-making is rather limited.

Despite the need for change, fisheries advice in Western democracies operates as a well-engrained machinery. Any new proposals face inertia and concerns about the integrity and credibility of the process. Addressing them calls for avoiding disruption. In this sense, the use of the simulation tool known as Management Strategy Evaluation (MSE) to support fisheries decision-making under uncertainty has increased worldwide over the last thirty years. MSE fits well within the advisory process, providing stability and consistency with long-term management objectives. If successfully implemented, it allows understanding and assessing the consequences of management options, making trade-offs explicit, identifying strategies that work reasonably well balancing competing objectives.

In 2022, the Spanish Institute of Oceanography launched a research project focused on “New tools for mathematical modelling in the scientific advice of Spanish fisheries” (Math4Fish). The main goal was to improve stock assessment models, but it was also implemented as a test bench: from using models as a tool to set Harvest Control Rules to designing models as boundary objects for decision spaces. In this context, 'boundary objects' refer to models that serve as a common ground for different stakeholders, facilitating their interaction and understanding of the decision-making process. Combining modelling, population dynamics, and institutional analysis in an essential fishery for the country (Southern hake in the Bay of Biscay and Iberian Waters), an iterative and interactive process with fishers’ representatives, managers, and scientists took place through 2023-2024.

The findings show the capability of MSE to structure dialogue across stakeholders, allowing them to understand the likely consequences of their preferences and the potential uses of scientific evidence to support or discourage specific perceptions and demands. While debates on quota allocation often prompt a dead-lock between winners and losers, exploring objectives and how they trade off against one another generates decision spaces to choose balanced strategies. The interdisciplinary approach also allows the identification of frequently hidden factors. For instance, readiness to use the MSE framework is taken for granted. Readiness, however, goes beyond process design, technical expertise and models’ fitness to encompass context-dependent attributes such as the features of the management system and the actors involved. These findings contribute to reflecting on how to introduce changes in the current advisory system that avoid disruption while advancing integrated approaches.