MixME simulation loop

MixME uses a Management Strategy Evaluation simulation loop to dynamically project stocks and fleets forward in time. The key feature of this simulation loop is that management advice responds to the perceived state of the system and fishery dynamics are then constrained by this management advice.

There's a lot of flexibility here. At its simplest, management can be completely inflexible to changes in stock status, for example a constant catch rule. In this case, a constant level of target catch is given, that is then distributed over the fleets in the system. Fleets and stocks dynamically respond to management, but management does not change if the stocks begin to do poorly. A more complex (and also responsive) management procedure is one that uses a harvest control rule (HCR) to modify the target catch depending on stock status. In this case, fleets and stocks responds to management, but there is feedback from the system that informs subsequent management advice and this modifies subsequent fleet and stock dynamics.

Schematic of the Management Strategy Evaluation simulation loop.

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The performance of HCR-based management does not only depend on the suitability of the HCR, but also the accuracy of stock and fishery observations, the accuracy of stock status estimation, and any error in the implementation of management advice that leads to deviations from the catch target. These additional complexities are all features that can be built into your simulation!

The management procedures in MixME is modular, which allows for plenty of flexibility.

• Stock estimation
• Harvest control rules
• Advice