Using habitat-specific, spatial demographic information to improve stock assessments of groundfishes

Principal Investigator: Jameal Samhouri
Co-Principal Investigators: Jason Cope
External Collaborator: Scott Hamilton (Moss Landing Marine Laboratory)

Demographic rates and life history traits are the blocks upon which stock assessment models are built. In combination, individual parameters that describe recruitment, survival, growth, and reproduction dictate (un-)sustainable harvest rates. Natural mortality, fecundity and growth parameters set the absolute and relative biomass trends, as well as the productivity of a given stock, and directly determine population response to a given removal history within a stock assessment. Despite universal recognition of these principles, most assessment models used on the US West Coast have assumed (often due to data limitations) that there is not systematic variation in demographic rates and life history traits across this broad region, and thus most fisheries are informed at coarse resolution over large spatial scales. This approach can be problematic if population parameters vary geographically or among habitat types, as some populations may be overharvested while others may be underharvested. Thus, there is a critical need to develop analytical frameworks that explicitly incorporate regional and habitat-specific variation in demographic rates and life history traits.

The goal of our project is to (i) quantify demographic rates and life history traits for lingcod, Ophiodon elongatus, in rocky and soft bottom habitats in 5 latitudinally distinct regions along the US West Coast (from Washington to southern California), and (ii) evaluate how application of differences in life history traits to population models leads to new insights about ways to obtain more productive and sustainable lingcod yields. Lingcod will be collected and dissected to determine key parameters for population assessment models, including: weight-length, age and growth, size and age at maturity, diet, batch fecundity, condition factor, and mortality. We will use this information to parameterize a heuristic population dynamics model that investigates the consequences of life history differences for sustainable harvest practices. A re-assessment of lingcod is planned in the next year or two, and we hope that the new information we provide will help to inform it.

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Northwest Fisheries Science Center (NWFSC)


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