Resource Ecology & Fisheries Management (REFM) Division

Status of Stocks & Multispecies Assessment Program

Groundfish Stock Assessments for 2006

Fishery Quota Recommendations

Figure 1.  Relative 2006 spawning stock size compared to Bmsy (taken to be B35% for all species except EBS pollock) versus relative 2005 catch levels compared to 2005 Fmsy levels for BSAI stocks.

The Alaska groundfish management system is based on extensive data available from the NMFS Observer Program and dedicated research cruises. Catch of target and prohibited species (e.g., salmon, crab, herring, and Pacific halibut) are estimated at sea or in processing plants to provide real time information to ensure that fisheries do not exceed total allowable catches (TACs) or violate other fishery restrictions (like time-area closures). Dedicated research cruises coupled with observer data make it possible to build detailed population dynamics models. Results of these modeling activities are used to determine the status of individual species.

Establishing TACs involves annual evaluation of the best available scientific information through a series of documents and public meetings. The first step begins with the preparation of stock assessment and fishery evaluation (SAFE) reports. These reports contain analyses summarizing the information about the individual stocks and groups, and include acceptable biological catch (ABC) and overfishing level (OFL) recommendations for future years. The authors of these reports, generally NMFS scientists, present their findings to the North Pacific Fishery Management Council’s (NPFMC) groundfish Plan Teams in September and November.

Figure 2.  Relative 2006 spawning stock size compared to Bmsy (taken to be B35% for GOA stocks) versus relative 2005 catch levels compared to 2005 Fmsy levels for GOA stocks.

At these meetings, the reports are reviewed, and recommendations for ABC levels are compiled into two SAFE report volumes (one each for the Bering Sea/Aleutian Islands (BSAI) and Gulf of Alaska (GOA) regions) along with Plan Team recommendations for ABC, which may differ from author recommendations. The compiled reports are then submitted to the NPFMC Scientific and Statistical Committee (SSC) for further review. The SSC makes the final ABC recommendation to the Council and the Council’s Advisory Panel of industry representatives makes TAC recommendations. Finally, the recommended TAC levels are adjusted (for some species) by the Council to ensure that other constraints (e.g., limiting the sum of all TACs in the Bering Sea and Aleutian Islands to be less than 2 million t) are met. The following rule applies for all federally managed groundfish species in a given year: Catch < TAC < ABC < OFL

In practice, catch is often much less than TAC and TAC is often much less than ABC. The multispecies management system is, therefore, based on the premise that no individual components are overfished or below stock sizes that are considered detrimental to the ecosystem. Stock assessments can be obtained at: http://www.afsc.noaa.gov/refm/stocks/assessments.htm.

In 2005 the Resource Assessment and Conservation Engineering (RACE) Divison’s groundfish assessment group conducted a summer bottom trawl survey in the Gulf of Alaska (the previous such survey was in 2003). This survey, together with past estimates, indicate that groundfish biomass levels have increased from below 5 million t total in 1984 and 1987 to over 7 million t in 2003 and 2005. The main species groups to increase over this period were rockfish and arrowtooth flounder whereas other flatfish, Pacific cod, and walleye pollock show general declines.

RACE’s Midwater Assessment and Conservation Engineering (MACE) group conducted three major surveys in 2005: the winter echo integration-trawl survey in the Shelikof Strait and nearby areas, the winter Bogoslof Island region survey of spawning pollock from the Aleutian Basin, and preliminary summer work developing a broader-scale echo integration-trawl survey within the GOA.

Auke Bay Laboratory (ABL) scientists conducted the annual longline survey which is designed primarily for sablefish but also produces data used in Greenland turbot and some rockfish assessments. This survey covers the slope regions of the GOA along with segments of the Bering Sea and Aleutian Islands regions. The RACE Division’s groundfish assessment group also conducted the standard summer-trawl survey for the EBS shelf area. Data from these main survey efforts are critical for groundfish stock assessments.

Ecosystem considerations sections were enhanced within individual assessment sections in addition to the 314 page document detailing an overall picture of the ecosystem status, available on the web at http://www.afsc.noaa.gov/refm/docs/2005/EcoChpt.pdf.

Figure 3.  Spawning biomass trends for Bering Sea and Aleutian Islands (BSAI) and Gulf of Alaska (GOA) for all groundfish stocks combined (sablefish spawning biomass is included in the GOA total).

Presently, projections of 2006 spawning biomass for the main groundfish stocks are estimated to be above their target stock size (B_msy) and the 2005 catch levels were below F_msy levels for both the BSAI and GOA regions (Figs. 1 and 2 above). Combined spawning biomass estimates for the main species in these regions appear to be stable overall (Fig. 3). Fisheries for these groundfish species during 2004 yielded 2.0 million metric tons (t) valued at approximately $1.7 billion after primary processing.

The main pollock stock remains high and again yielded catches just over 1.5 million t. Virtually all flatfish resources (e.g., rock sole, yellowfin sole, Alaska plaice, and arrowtooth flounder) are at high and healthy levels but catches remain relatively low. Atka mackerel abundance is stable and at above-average levels. Rockfish species comprise 5%-8% of the groundfish complex biomass and are generally increasing based on recent surveys. For the main stocks with age-structured analyses, the spawning biomass trends compared with the average levels since 1977 are shown in Figure 4 (below) for the GOA and BSAI. These figures suggest that stock conditions are fairly evenly split between those that are above average and below in the past few years.

Figure 4.  Biomass trends for Gulf of Alaska (GOA) and Bering Sea and Aleutian Islands (BSAI) stocks relative to their mean level, 1978-2004

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AFSC Quarterly
Research Reports Oct-Dec 2005