Resource Ecology & Fisheries Management (REFM) Division
Status of Stocks and Multispecies Assessment Program
Groundfish Stock Assessments for 2007: Fishery Quota Recommendations
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., Pacific 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 and make recommendations for future catch levels.
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 levels (OFL) recommendations for future years. The authors of these reports, generally NMFS scientists, present their findings to the North Pacific Fishery Management Councilís (NPFMC) groundfish Plan Teams in September and November of each year. 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 Councilís 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 metric tons (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.
Figure 1. Relative 2007 spawning stock size compared to Bmsy (taken to be B35% for all species except EBS pollock) versus relative 2006 catch levels compared to 2006 Fmsy levels for BSAI stocks.
Figure 2. Relative 2007 spawning stock size compared to Bmsy (taken to be B35% for GOA stocks) versus relative 2006 catch levels compared to 2006 Fmsy levels for GOA stocks.
In 2006 the Resource Assessment and Conservation Engineering (RACE) Divisionís groundfish assessment group conducted a summer bottom trawl survey in the Aleutian Islands (the previous such survey was in 2004). This survey, together with past estimates, indicate that groundfish biomass levels have increased from slightly below 2 million t (1991-2000 survey averages; all groundfish) to just over 2.7 million t average biomass from the 2002, 2004, and 2006 surveys.
The predominant species in this region include Atka mackerel (32% of the total biomass) and Pacific ocean perch (22% of the total biomass) based on average levels from the Aleutian Islands surveys from 1991 to 2006. Pollock represent only about 9% of the biomass based on the survey followed by northern rockfish (7%), Pacific cod (6%) and giant grenadier (6%). Arrowtooth flounder has averaged only 4% of the biomass estimated in the Aleutian Islands but has shown a marked increase since the 1991, 1994, 1997, and 2000 average level of 55 thousand t to over 122 thousand t average biomass for 2002, 2004, and 2006. In 2006, the number of survey tows was reduced by about 15% of normal due to budget constraints, however the area covered by the Aleutian Islands survey was maintained.
RACEís Midwater Assessment and Conservation Engineering (MACE) group conducted three major surveys in 2006: the winter echo-integration trawl (EIT) survey in the Shelikof Strait and nearby areas, the winter Bogoslof Island region survey of spawning pollock from the Aleutian Basin, and the entire shelf region of the EBS to assess the summer abundance of pollock and other species. Auke Bay Laboratory scientists from the Marine Ecology and Stock Assessment (MESA) Program 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 Divisionís groundfish assessment group also conducted the standard summer-trawl survey for the EBS shelf area. Due to budget limitations, the planned 2006 EBS slope survey was cancelled. 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 360 page document detailing an overall picture of the ecosystem status, available on the AFSC web site at http://www.afsc.noaa.gov/refm/docs/2006/EcoChpt.pdf. This report plays an ever increasing role in evaluating quota recommendations and ecosystem considerations are continually being enhanced within the individual species-specific stock assessment report sections.
Presently, projections of 2007 spawning biomass for the main groundfish stocks are estimated to be above their target stock size (Bmsy) and the 2006 catch levels were below Fmsy levels for both the BSAI and GOA regions (Figs. 1 and 2). Fisheries for these groundfish species during 2005 yielded 2.1 million t valued at approximately $2.0 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 levels, but catches remain relatively low. Atka mackerel abundance continues to be at above-average levels. Rockfish species comprise 5%-8% of the groundfish complex biomass and are generally increasing based on recent surveys.