2014 Assessment of the Dusky 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. Please refer to last year’s full stock assessment report for further information regarding the assessment model.
We use a statistical age-structured model as the primary assessment tool for Gulf of Alaska dusky rockfish 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.
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 catch estimates for this year’s projection model are an updated 2013 catch of 3,158 t, and estimated 2014-2016 catches of 3,106 t, 3,379 t, and 3,124 t, respectively. The 2014 catch was estimated by multiplying the official catch as of October 1, 2014, by an expansion factor of 1.03, which represents the average fraction of catch taken between October 1 and December 31 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 aren’t available at this time, an estimated 200 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 (0.67), 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 2013 assessment model to generate catches for those years. The yield ratio was higher than last year’s ratio of 0.63 whereas the expansion factor was the same as last year’s expansion factor.