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Resource Ecology & Fisheries Management (REFM) Division

Status of Stocks & Multispecies Assessment Program

Groundfish Stock Assessments for 2006:  Bering Sea/Aleutian Islands (BSAI)

The sum of the ABCs for 2006, as recommended by the North Pacific Fishery Management Council’s Scientific and Statistical Committee, is just over 3 million t, approximately 32,000 t less than the sum of the 2005 ABCs representing a difference of about 1%. In 2006, the biennial summer bottom-trawl survey of the Aleutian Islands region is planned, as is the EBS slope area. Additionally, the biennial summer EIT survey of the EBS shelf region will be conducted along with the winter Bogoslof region EIT survey. The standard summer bottom trawl survey is also planned. These surveys will provide critical information for developing 2006 assessments and further management recommendations. Summaries of each stock/assemblage group are presented as follows.

EBS Pollock:  The 2005 bottom-trawl survey estimate of the pollock stock in this region is 37% higher than the 2004 estimate but only 5% higher than the long-term average estimate since 1982. Other new data in this year’s assessment includes revised age composition estimates from the 2004 EIT survey, new age composition estimates from the 2004 fishery, and age composition estimates from the 2005 survey. Maturity data from a study completed by Jennifer Stahl (UAF Juneau) were evaluated in this year’s assessment.

The current state of the population (as projected to 2006) is estimated to consist mainly of the 2000 year class (estimated biomass at about 2.6 million t or 28% of the total) whereas 31% of the 2006 pollock biomass is estimated to be aged 1-3 years (Fig. 5 below). The Council recommended a 2006 ABC of 1.93 million t while the 2006 TAC for this management stock was set at 1,485,000 t. Projections for 2007 suggest population declines but these will be revised when the planned 2006 EIT and bottom-trawl surveys are complete and analyzed.

EBS pollock biomass chart
Figure 5.  EBS pollock biomass by age groups as projected for 2006.

Aleutian Islands Pollock:  The Council accepted the age-structured analysis but for precautionary reasons, recommended ABC and TAC levels of 29,400 t and 19,000 t, respectively, which is well below the maximum permissible ABC level of 43,200. They reiterated the need for more comprehensive surveys during the time when pollock fishing traditionally occurred in this region. To this end, NMFS is preparing a proposal for industry-cooperative research to develop alternative management measures that might allow for directed pollock fishing while also minimizing the potential interaction effects with Steller sea lions.

Bogoslof Island Pollock:  A new age-structured assessment was presented for pollock in this region in 2005. The motivation for developing this model was partly due to the fact that the spawning-ground survey data extends over 16 years and that even though this area has been closed to pollock fishing since 1992, the stock has remained at stable but low abundances compared to peaks observed during the late 1980s. The Council encouraged this study and requested that further analyses be conducted relative to fisheries on “Aleutian Basin” pollock (e.g., those caught in the international zone of the Central Bering Sea). The 2006 ABC was specified as in previous years which (based on the most recent survey estimate) results in a value of 5,500 t. The Council set the TAC for this area at 10 t to allow for bycatch in other fisheries.

BSAI Pacific Cod:  The 2005 EBS shelf bottom-trawl survey estimate (603,800 t) for Pacific cod is up by 1% compared to the 2004 estimate but is 26% below the average of all survey biomass estimates since 1982. The assessment was done using new software that allowed a number of enhancements over previous analyses. More significantly, revised estimates of maturity-at-age were used based on recent studies completed by James Stark (RACE Division). These new estimates resulted in substantially higher estimates of spawning biomass for a given population numbers-at-age estimate, but other factors in tuning the model resulted in biomass levels that were generally lower than previously estimated. The Council-selected model resulted in an ABC (and TAC) of 194,000 t compared to the 2005 level of 206,000 t.


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