Science & Data

Rockfish of the genus Sebastes are found in temperate waters of the continental shelf off North America. At least thirty-two species of Sebastes occur in the Gulf of Alaska. The DSR assemblage is comprised of the seven species of nearshore, bottom-dwelling rockfish (Table 1). These fish are located on the continental shelf, reside on or near the bottom, and are generally associated with rugged, rocky habitat. For purposes of this report, emphasis is placed on yelloweye rockfish, as it is the dominant species in the DSR fishery (O’Connell and Brylinsky 2003).

The "flatfish" species complex previous to 1990 was managed as a unit in the Gulf of Alaska (GOA). It included the major flatfish species inhabiting the region, with the exception of Pacific halibut. The North Pacific Fishery Management Council divided the flatfish assemblage into four categories for management in 1990; "shallow flatfish" and "deep flatfish", flathead sole and arrowtooth flounder. This classification was made because of significant differences in halibut bycatch rates in directed fisheries targeting the shallow-water and deepwater flatfish species. Arrowtooth flounder, because of high abundance and low commercial value, was separated from the group and managed under a separate acceptable biological catch (ABC). Flathead sole were likewise assigned a separate ABC since their distribution over depths overlaps with that of the shallow-water and deepwater groups. In 1993, rex sole was split out of the deepwater management category because of concerns regarding the bycatch of Pacific ocean perch in the rex sole target fishery.

Gulf of Alaska (GOA) Atka mackerel have 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 only provided an expanded executive summary with updated catch and the 2013 survey information, due to the government shut-down in October 2013. In 2014, we again presented an executive summary in keeping with the biennial schedule.

Arrowtooth flounder (Atheresthes stomias) range from central California to the eastern Bering Sea and are currently the most abundant groundfish species in the Gulf of Alaska. Arrowtooth flounder occur from central California to the Bering Sea, in waters from about 20m to 800m, although catch per unit effort (CPUE) from survey data is highest between 100m and 300m. Migration patterns are not well known for arrowtooth flounder; however, there is some indication that arrowtooth flounder move into deeper water as they grow, similar to other flatfish (Zimmerman and Goddard 1996). Fisheries data off Washington suggest that larger fish may migrate to deeper water in winter and shallower water in summer (Rickey 1995). Arrowtooth flounder spawn in deep waters (>400m) along the continental shelf break in winter (Blood et al. 2007). They are batch spawners, spawning from fall to winter off Washington State at depths greater than 366m (Rickey 1995).

The National Standard Guidelines for Fishery Management Plans published by the National Marine Fisheries Service (NMFS) require that a stock assessment and fishery evaluation (SAFE) report be prepared and reviewed annually for each fishery management plan (FMP). The SAFE reports are intended to summarize the best available scientific information concerning the past, present, and possible future condition of the stocks and fisheries under federal management. The FMPs for the groundfish fisheries managed by the Council require that drafts of the SAFE reports be produced each year in time for the December North Pacific Fishery Management Council (Council) meetings.

Federal fisheries conducted in waters off Alaska are some of the largest in the world. In 2013, almost 2.4 million metric tons (t) of fish and shellfish were commercially harvested in waters off Alaska, which was just over half of the total catch in U.S. waters (NMFS 2013a). Many of these fisheries are governed by the Magnuson-Steven Fishery Management and Conservation Act (MSA), which, among other things, requires establishing fishery management plans (FMPs) that are consistent with the MSA and its National Standards. The management of Federal groundfish fisheries off Alaska is governed under FMPs that are specific to the Bering Sea and Aleutian Islands (BSAI) and Gulf of Alaska (GOA) regions (Fig. 1). The catch of FMP species is monitored using landing and production information that is reported by the commercial fishing industry and at-sea information collected from an extensive at-sea observer program. These data sources are integrated into a NMFS application called the Alaska Catch Accounting System (the CAS) and used to produce the total catch estimates referenced in the FMPs.

Analyses of new data (namely size and age composition data for 2013 – 2015) made available in September 2015 exacerbated a data conflict with the NMFS EBS Shelf and Slope trawl surveys necessitating unexpected model configuration changes to resolve what are clear structural misspecifications. The EBS shelf survey provides a reasonable index of young fish but as they age, they clearly exit the survey area. The EBS slope survey provides an index of adult fish and typically occurs every other year (except that the 2014 survey was dropped so the most recent data is from 2012). Initial runs of the 2014 Model with the new data (Model 14.0) suggested that recent high recruitment estimates (2007-2010) are closer to average, likely reflecting a change in the availability of these fish to the Shelf survey gear. Re-weighting shelf and slope survey composition data to better account for shifts in distribution relative to survey gear appears to improve model diagnostics while acknowledging that Greenland turbot are distributed to a large degree outside the survey areas and are affected by thermal conditions (shifting further north in warmer years in the EBS).

In 2005, Bering Sea/Aleutian Islands (BSAI) rockfish were moved to a biennial assessment schedule to coincide with the frequency of trawl surveys in the Aleutian Islands (AI) and the eastern Bering Sea (EBS) slope. These surveys occur in even years, and for these years a full assessment of shortraker rockfish in the BSAI area are conducted. The shortraker assessment is conducted with Tier 5 methods. In this methodology, an exploitation rate is applied to the estimated current biomass to obtain the acceptable biological catch (ABC) and overfishing limit (OFL).

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. Alaska skate (Bathyraja parmifera), the most abundant skate species in the BSAI, is in Tier 3 so harvest recommendations are made using the results of an age-structured model. 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.

The shark complex (Pacific sleeper shark, spiny dogfish, salmon shark and other/unidentified sharks) in the Bering Sea and Aleutian Islands (BSAI) is assessed on a biennial stock assessment schedule in even years to coincide with RACE Eastern Bering Sea trawl surveys. BSAI sharks are a Tier 6 complex with the OFL based on maximum historical catch between the years 1997 – 2007 (ABC is 75% of OFL). For this off-year summary, we have updated the time series of catch through Oct 1, 2015 to reflect any changes that might have occurred in the Catch Accounting System (for the years 2003 – 2015). The estimates for 1997 – 2002 were determined by simulating the catch estimation algorithm used for target species in what was formerly called their “blend catch estimation system” and so updated data for those years are not available in CAS (Gaichas 2002 and 2003). There were no changes in catch estimates from 2003 – 2007, thus there were no changes to the proposed ABC/OFL from 2014.