Potential Consequences of Possible Mismatched Ecological and Regulatory Scales on the Stock Assessment and Management of Gulf of Maine Cod Fishery

Recent research indicates that Gulf of Maine (GOM) cod once considered panmixtic is actually more likely metapopulation. This stock probably consists of several subpopulations adapted to local environmental conditions, showing spatial and temporal diversities in life history processes and the ways they interact with the biophysical environment. However, GOM cod has long been assessed and managed as a unit stock. This regulatory scale is not well matched with the ecological scale, probably resulting in substantially biased stock assessment and mismanagement. A simulation study is conducted to quantify the consequence of mismatched ecological and regulatory scales on the stock assessment and management of GOM cod. An age-structured model of three substocks is developed based on the data available for the GOM cod stock. We explore the model with two possible stock recruitment scenarios, three levels of mixing, and three distribution patterns of fishing mortality. Impacts of these different parameterizations on stock assessment estimates and predicted stock status are evaluated. Preliminary results show that misspecification of the regulatory scale of GOM cod with respect to the ecological scales is likely to cause biased stock assessment estimates, putting the overall stock at risk and even leading to local depletion.