Developing fisheries models of intermediate complexity to address spatial dynamics and species interactions

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Models of intermediate complexity for ecosystem analysis (MICE) have been proposed as decision support tools for fisheries management. MICE limit complexity by focusing on ecosystem components that are required to address the main effects of the management questions of interest. MICE thereby address some of the impediments to wider use of ecosystem models in fisheries management. Despite their appeal, MICE have seen few applications due to the substantial data requirements for this approach and a scarcity of scientists with the computer modeling and statistical expertise required. Working with BC Ministry of Environment scientists my group developed a MICE that could evaluate yield outcomes of different fishery regulations for the Kootenay Lake trophy trout fishery. A model that included predator-prey interactions fitted the predator-prey abundance data better and predicted yields 25% higher than models that did not include predator-prey interactions. With the collapse of the trophy trout fishery in 2015, fishery managers have requested a MICE to evaluate the consequences of different management options that could rebuild the fishery. DFO and fishery stakeholders recently used management strategy evaluation (MSE) results for Atlantic redfish that were computed by my group to narrow the list of different management procedures (MPs) from over 30 to 5 for further consideration. Preliminary analyses suggested that range contraction in the stocks, i.e., decreases in spatial distribution coinciding with decreases in fish abundance, could imply that stock declines could be much less than assessed in the MSE. To increase the usefulness of MICE, I propose to investigate the following: (1) In a large lake ecosystem, i.e., Kootenay Lake, evaluate the effects of trophic and predator-prey interactions on the population dynamics of fish stocks and the yield and conservation outcomes of different MPs. My group will develop and apply a MICE that is fitted to data and will enable evaluations of different combinations of management actions to promote recovery of the recently collapsed trophy trout fishery. (2) For a widely distributed fish stock, i.e., Atlantic redfish, evaluate the effects of range contraction on assessed trends in abundance, population productivity and species interactions, and the yield and conservation outcomes of different MPs. My group will develop, fit to data and apply MICE to evaluate different MPs under joint scenarios for range contraction and species interactions. 2 MSc and 2 PhD students and one post doc will be trained in MICE and MSE modeling. The modeling results obtained in the proposed work could help to inform decisions that could restore and increase the value of the Kootenay Lake fishery by up to $10 million per year. If corrections were made to the redfish MSE to account for range contraction, sustainable yields and the associated wealth generated could be 20,000 t higher and $40 million higher per year.