Predicted effects of marine protected areas on conservation and catches are sensitive to model structure

• DOI: 10.1007/s12080-024-00602-7
• Publication Date: 2025-01-03T00:17:50Z
• Authors: Daniel Ovando

Use of Marine Protected Areas (MPAs) are expanding around the world. MPAs can have a wide variety of objectives (e.g. conservation, food security, cultural value), and scientific guidance on how to design MPAs to achieve objectives is generally based on simulation modeling. While certain questions require specific types of models, in other cases many different models may all provide an answer to questions such as the predicted change in population biomass and fisheries catches resulting from implementation of an MPA. When multiple levels of model complexity are all in theory capable of answering the same question, and the models cannot be confronted with data directly, the decision of what level of model complexity to use can be *ad hoc*. In this, paper I compare the effects of MPAs on catch and biomass predicted by a spatially explicit age-structured multi-species and multi-fleet (*High-definition*) model to the predictions generated by a two-patch surplus production (*Low-definition*) model, fitted to emulate the *High-definition* model. I found that in many cases the predictions made by the two models were markedly different, with the *Low-definition* model frequently predicting substantially higher biomass benefits from MPAs than the *High-definition* model, and in some cases incorrectly estimating the direction (positive or negative) of the MPA effects. However I also show that the *Low-definition* model has strategic value for ranking exercises. Our results show that care should be taken in selecting and interpreting the results of MPA simulation models, and that research is needed to understand what models are best suited to what policy recommendations when multiple viable options exist.