2016 Assessment of the Northern and Southern Rock Sole Stocks in the Gulf of Alaska
Assessment for northern and southern rock sole which are part of the shallow water flatfish complex has been moved to a biennial schedule to coincide with the expected receipt of new survey data. Usually, on alternate (even) years we will present an executive summary with last year’s key assessment parameters and projections for this year.
Changes in the input data: The new information available are the updated 2015 catch for rock sole of 2,622 t and the partial 2016 catch of 2,702 t through October 13. Projected catch to the end of 2016 using the average fraction of catch to October 13 from the last 10 years (84.3%) would be 3,205 t. Catch in 2017 was set at the estimated 2016 catch.
Changes in the assessment methodology: The input catches for 2015, 2016 and 2017 were changed otherwise there were are no changes to the assessment methodology. Biomass, OFL and ABC values for northern and southern rock sole are estimated using projections from the 2015 assessment model with catches updated for 2015 and 2016. Catches of rock sole in 2015 and 2016 were split evenly between northern and southern rock sole for projections. The total catch in 2016 for rock sole (3,205 t) was estimated using the average fraction of catch to October 13 over the last 10 years (0.843) and the estimated catch to October 13, 2016 (2,702 t). The total catch estimate for 2016 was used as the catch in 2017 for projections. 2017 biomass, OFL and ABC estimates were lower for projections from the 2015 assessment because 2016 catch was set at the ABC (A’mar, et al. 2015). The 2016 catch (3,205 t) used in the current projections for 2016 and 2017 was lower than the ABC estimates for both northern and southern rock sole (27,400 t).
The biomass, OFL and ABC values for northern and southern rock sole are added into the shallow-water flatfish complex values to estimate OFL and ABC for the complex.