2019 Assessment of the Northern Rockfish Stock in the Gulf of Alaska

In 2017, the scheduled frequency for some stock assessments was changed in response to the National Stock Assessment Prioritization effort. Prior to 2017, Gulf of Alaska (GOA) rockfish were assessed on a biennial stock assessment schedule to coincide with the availability of new trawl survey data. Under the new schedule, full assessments for northern rockfish will be conducted in even years and partial assessments will be presented in odd years. For Gulf of Alaska northern rockfish in 2019, we present a partial assessment to recommend harvest levels for the next two years. Please refer to the 2018 Assessment of the Northern Rockfish Stock in the Gulf of Alaska (PDF, 89 pages) for further information regarding the assessment model (Cunningham et al., 2018). A full stock assessment document with updated assessment and projection model results will be presented in next year’s SAFE report (2020).

We use a statistical age-structured model as the primary assessment tool for GOA northern rockfish stock which qualifies as a Tier 3 stock. This assessment consists of a population model, which uses survey and fishery data to generate a historical time series of population estimates, and a projection model, which uses results from the population model to predict future population estimates and recommended harvest levels. The data sets used in this assessment include total catch biomass, fishery age and size compositions, trawl survey abundance estimates, and trawl survey age compositions. For a partial assessment, we do not re-run the assessment model, but do update the projection model with new catch information. This incorporates the most current catch information without re-estimating model parameters and biological reference points.