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Status of Stocks & Multispecies Assessment Program

Groundfish Stock Assessments for 2008:  Bering Sea/Aleutian Islands (BSAI)

Figure 4, see caption
Figure 4.  Click image to enlarge.
 
 

The sum of the ABCs for 2007, as recommended by the Scientific and Statistical Committee, is just over about 2.4 million t, about 10% lower than the sum of the 2007 ABC values. This drop was driven by the continued reduction in ABC from EBS pollock (1.45 million t in 2007 compared to 1.0 million t in 2008). Brief summaries of each BSAI species or species group follows.

EBS Pollock:  The 2007 summer bottom-trawl survey estimate of the pollock stock increased from the 2006 estimate but was only about 87% of the long-term mean for this survey. Similarly, the 2007 EIT survey estimate increased over the 2006 estimate but was still only about 55% of the long-term mean for this survey. Abundances at age patterns as observed in NMFS groundfish trawl surveys are shown in Figure 4. Combined with new information on the age composition from NMFS observer data and these surveys, and lower-than-expected mean weights-at-age for pollock observed from the 2006 fishery, the projections for 2008 and 2009 are lower than what was estimated last year. The Council recommended a 2008 maximum permissible Tier 1b ABC of 1.170 million t. Additionally, they decided that more precaution was required and decided that it would be most prudent to have the ABC set at 1.0 million t which would return the spawning biomass exploitation rate to pre-2006 levels. For the near term, the expected trends are for the declines to ease and abundance to increase in 2010 as the apparently above-average 2006 year class recruits to the population.

Aleutian Islands and Bogoslof Region Pollock:  The Aleutian Islands pollock spawning biomass is projected to be over 82,000 t in 2008 and above the B40% level of 51,500 t, which results in an ABC level of 28,200 t. However, due to current regulations, the TAC for this region is set to 19,000 t. For Bogoslof pollock, winter survey results show a stable to slightly increasing stock with an ABC (under Tier 5) set to about 8,000 t. However, consistent with past practices, the Council prohibits a directed pollock fishery in this region and recommended a TAC of 10 t to account for pollock bycatch that occurs in other fisheries.

BSAI Pacific Cod:  The 2007 EBS shelf bottom-trawl survey estimate was 424,000 t, representing a drop of 18% from the 2006 value, and is the all-time low in the time series. The assessment evaluated an array of model configurations. As with past years, the models indicated a series of poor year classes (2001-05). However, the 2006 year class appears to be more than 2.5 times higher than the average recruitment. The Council-selected model resulted in an ABC (and TAC, not counting state-waters allocation) of 176,000 t.

BSAI Flatfish:  Combined, the five main species groups of flatfish (not counting Greenland turbot) continue to trend upwards with a 24% increase from the 2007 levels of ABC (representing about 43% of all groundfish). As with last year, the Council accepted that estimates of Fmsy and the associated uncertainty were adequately estimated, based on fitting a stock-recruitment relationship within the integrated assessment model, for yellowfin sole and northern rock sole. This results in management under Tier 1 and implies somewhat higher ABCs than estimated under Tier 3 methods. Critically important this year is the fact that the TAC for yellowfin sole has been set to 225,000 t-an increase of 65% from the 2007 level. This is due to the decrease in pollock TAC and will potentially have important repercussions on future harvest rates and halibut bycatch levels. The arrowtooth flounder 2008 ABC increased 54% to 244,000 t but led to a TAC of only 75,000 t. Northern rock sole 2008 ABC increased by 52% (primarily due to increasing survey estimates and Tier 1 calculations) to 301,000 t but the TAC was set at 75,000 t. The flathead sole ABC dropped by 9% to 71,700 t while the Council set the TAC to 50,000 t. Alaska plaice and other flatfish assemblage ABCs increased by just over 1% from the 2007 levels leading to a combined TAC of 71,600 t.

BSAI Greenland Turbot:  Surveys suggested a slight decline from previous year's results but still indicated that recent recruitment conditions improved. A number of issues remain with this assessment, in particular, the fact that this species tends to be distributed in more northerly regions and the degree of mixing between other regions (e.g., north of the U.S. convention line) is unknown. Due to funding limitations, the slope survey (which covers the main habitat for Greenland turbot) was cancelled in 2006, but it is hoped that one will be conducted in 2008. Due to the assessment uncertainties and stock structure issues, the Council recommended a conservative ABC level, which for 2008 is 2,540 t.

BSAI Rockfish:  Since the main survey in the Aleutian Islands was most recently conducted in 2006, the BSAI rockfish stock assessments were updates of projections from last year's models. The only change was noted for the BSAI Pacific ocean perch ABC, which dropped 1% to 21,600 t for 2008. Northern rockfish and the other species shortraker and rougheye rockfish, and "other" rockfish biomass levels were reported as stable based on projections.

BSAI Atka Mackerel:  The assessment model results indicate that the stock is declining from above-average levels, and the projected 2008 biomass estimate results in a decline of about 18% from the 2007 ABC level. The projected female spawning biomass for 2008 is estimated at 110,200 t, roughly 47% of unfished spawning biomass and above the B40% level (94,000 t). The 2008 ABC recommendation is 60,700 t (which is also equal to the TAC). This is down from the 2007 level of 74,000 t.

By James Ianelli
 

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