2014 Assessment of the Skate Stock Complex in the Bering Sea and Aleutian Islands
March 04, 2014
The Bering Sea and Aleutian Islands (BSAI) skate complex is managed in aggregate, with a single set of harvest specifications applied to the entire complex. However, to generate the harvest recommendations the stock is divided into two units. Harvest recommendations for Alaska skate Bathyraja parmifera, the most abundant skate species in the BSAI, are made using the results of an age structured model and Tier 3. The remaining species (“other skates”) are managed under Tier 5 due to a lack of data. The Tier 3 and Tier 5 recommendations are combined to generate recommendations for the complex as a whole.
In response to the 2013 review by the Center of Independent Experts (CIE), and as part of an ongoing process to improve skate assessments, the BSAI Alaska skate model has been completely reworked for 2014. The most fundamental change is a lengthening of the model time period: the preferred model’s start year is 1950, all of the EBS shelf survey data from 1982-present are included, and a reconstruction of historical catches extends the catch time series back to 1954. The model was also simplified, especially in
relation to the 2012 model revision. This report presents the existing (i.e. 2012) model, the author’s preferred new model, and two additional models requested by the Plan Teams and the SSC. Selected results of all four models are included for purposes of comparison; full model results are included only for the author’s preferred model.
Also new for 2014, the random effects (RE) model created by the survey averaging working group of the Joint Plan Teams was used to create biomass estimates for “other skates” and to make harvest recommendations for that group.