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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)  (cont.)

BSAI Flatfish:  Combined, the five main species groups of flatfish have continued to trend upwards with a 6% increase from the 2005 level to 6.87 million t. This level is 23% higher than the average of the biomass estimates for all EBS shelf surveys since 1982.

The yellowfin sole 2006 ABC dropped 2% from last year to 121,000 t, which led to a TAC of 95,701 t. The arrowtooth flounder 2006 ABC increased 26% to 136,000 t, which led to a TAC of 13,000 t. Northern rock sole 2006 ABC declined by 5% to 126,000 t and a TAC of 41,500 t. The flathead sole ABC increased by 2% to 59,800 t while the Council set the TAC at 19,500 t. Alaska plaice 2006 ABC was stable (decline of 1%) at a value of 188,000 t and a 2006 TAC of 8,000 t. The other flatfish assemblage 2006 ABC dropped 15% to 18,100 t, but the TAC was set to 3,500 t.

BSAI Greenland Turbot:  This stock continues to decline, perhaps reflecting generally warmer conditions. This species tends to be distributed in more northerly regions and the degree of mixing between other regions (e.g., north of the US convention line) is unknown. Assessment uncertainties and stock structure issues has led the Council to recommend conservative ABC levels, which for 2006 is 2,740 t, well below the maximum permissible value of 11,400 t.

BSAI Rockfish:  Since these species are generally long-lived and less common on the EBS shelf (where annual surveys occur) the Council has approved of a biennial cycle for conducting full assessments of these species to coincide with the timing of surveys. A bottom-trawl survey in the Aleutian Islands is planned for 2006 and when these data are available, a full assessment will be undertaken.

Projected stock trends for Pacific ocean perch in the BSAI resulted in a 2006 ABC recommendation of 14,800 t compared to the 2005 level of 14,600 t. For northern rockfish the 2006 ABC increased by 3% relative to the 2005 value to 8,530 t. Shortraker rockfish 2005 ABC recommendations decreased by 3% from last year’s levels giving 580 t, while the ABC for rougheye rockfish and other rockfish remained the same at 224 t.

BSAI Atka Mackerel:  New information on fishery and survey age composition resulted in slightly different model results compared to the 2004 assessment. In particular, the revised estimates of age structure resulted in 2005 model estimates of age 3+ biomass that were 10% higher compared to the assessment prepared in 2004, but still with a declining biomass trend through 2006 and 2007. This resulted in 2006 ABC recommendations that were down by 11% (to 110,000 t) compared to the 2005 ABC.

The Council’s 2006 TAC recommendation for Atka mackerel is 63,000 t, which is the same as the TAC for 2005. The Council and AFSC scientists are interested in exploring the extent that Atka mackerel occurring in the GOA may be related to the BSAI stock.

BSAI Other Species:  The authors presented comprehensive assessments and recommendations for setting group-specific ABCs and OFLs within this larger category of “other species.” The Council supported this idea but noted an FMP amendment needs to be developed for management. For squid, a reliable biomass estimate is lacking although the stock size relative to the catch is thought to be orders of magnitude greater.

Ecosystem model calculations suggest that about one million t of squid are consumed as prey annually. While highly uncertain, this tends to confirm that squid stock size is likely to be relatively large. For BSAI skates area-specific ABCs were recommended based on different species composition and relative abundances between the Bering Sea and Aleutian Islands, and the presence of endemic skate species found only in the Aleutian Islands.

Studies by Jerry Hoff (RACE) on skate nurseries may also play an important role in future management recommendations for this group. For BSAI sculpins, the biomass is second highest in this group following skates based on the EBS shelf bottom-trawl survey data. For BSAI octopus, biomass estimates based on trawl surveys suffer from high levels of sampling variability, seasonal differences in distribution, and gear selectivity. For the BSAI shark complex issues related to highly imprecise biomass estimates pose problems for deriving ABC recommendations.

The set of documents presented to the Council provides useful documentation for developing the needed FMP amendments. These issues will be discussed in greater detail during the February 2006 Council meeting to be held in Seattle.

By Jim Ianelli and Anne Hollowed (REFM) and Phil Rigby and Chris Lunsford (ABL)


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