2013 Assessment of the Atka Mackerel Stock in the Gulf of Alaska
April 23, 2013
Gulf of Alaska (GOA) Atka mackerel has been moved to a biennial stock assessment schedule to coincide with the availability of new survey data from the biennial trawl survey. A full assessment was presented in 2011, which included data from the 2011 GOA bottom trawl survey. On alternate (even) years we present an executive summary with updated catch, last year’s key assessment parameters, any significant new information available in the interim, and projections for this year. Although a survey was conducted in 2013, we provide an expanded executive summary with updated catch and new survey information as described below.
Due to the government shut-down in October 2013, stock assessments for an abbreviated suite of model runs are required only for Steller sea lion prey species (pollock, Pacific cod, Bering Sea/Aleutian Islands Atka mackerel), and species where a conservation concern has been noted. For all other Tier 1-3 stocks, updated projections from last year using 2013 catch data are required at a minimum. Results will be presented in executive summaries using the “off-year” format for stocks on biennial assessment cycles. For stocks managed in Tiers 4-6, executive summaries using the “off-year” format for biennial assessment cycles are required. Gulf of Alaska assessments that rely on trawl survey data for specifications will use the 2013 GOA trawl survey in the estimates of biological reference points and harvest recommendations.
Gulf of Alaska Atka mackerel have been managed under Tier 6 specifications since 1996 due to the lack of reliable estimates of current biomass. In 2007, the assessment presented Tier 5 calculations of ABC and OFL based on 2007 survey biomass estimates, for consideration. However the Plan Team and SSC agreed with the authors that reliable estimates of Atka mackerel biomass were not available and recommended continuing management under Tier 6. The 2011 assessment and 2012 update presented Tier 6 recommendations and did not present Tier 5 calculations given the large variances associated with the 2011 survey biomass estimates, which were essentially based on two significant hauls encountered in the western Gulf of Alaska. The Council set the Gulf-wide 2013 (and 2014) OFL, ABC, and TAC for Atka mackerel at 6,200 t, 4,700 t, and 2,000 t. The 2011 full assessment is available on the web (Lowe et al. 2011, http://www.afsc.noaa.gov/refm/docs/2011/GOAatka.pdf ).