2014 Assessment of the Northern Rockfish stock in the Gulf of Alaska
Rockfish are assessed on a biennial stock assessment schedule to coincide with the availability of new survey data. For Gulf of Alaska rockfish in alternate (even) years we present an executive summary to recommend harvest levels for the next two years.
We use a statistical age-structured model as the primary assessment tool for Gulf of Alaska northern rockfish stock which qualifies as a Tier 3 stock. For an off-cycle year, 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.
Summary of changes in Assessment Inputs
Changes in the input data: There were no changes made to the assessment model inputs since this was an off-cycle year. New data added to the projection model included an updated 2013 catch and new estimated catches for 2014-2016. New estimates for this year’s projection model are an updated 2013 catch at 4,879 t, and new estimated 2014-2016 catches. The 2014 catch was estimated by increasing the official catch as of October 1, 2014, by an expansion factor of 3%, which represents the average
percentage of catch taken after October 1 in the last three complete years (2011-2013). Since the 2014 rockfish directed fishery did not occur in the Western Gulf until October 15 and those catches are not available at this time, an estimated 1000 t (maximum estimated catch by in-season management) was added to the corrected 2014 total catch to better reflect the 2014 estimated catch. To estimate future catches, we updated the yield ratio to 0.86, which was the average of the ratio of catch to ABC for the last
three complete catch years (2011-2013). This yield ratio was multiplied by the projected ABCs for 2015 and 2016 from the updated projection model to generate catches for those years. The yield ratio was lower than last year’s ratio of 0.95 whereas the expansion factor was the same as last year’s expansion factor.
Changes in assessment methodology: There were no changes in assessment methodology since this was an off-cycle year.