Resource Ecology & Fisheries Management (REFM) Division

Status of Stocks & Multispecies Assessment Program

Groundfish Stock Assessments for 2006:  Gulf of Alaska (GOA)  (cont.)

GOA Rockfish:  Total rockfish biomass as estimated from the 2005 NMFS bottom trawl survey was nearly double the average value since 1984 with 707,000 t for the western and central GOA and 123,000 t in the eastern GOA. The largest increases from the 2005 survey were due to Pacific ocean perch (up 61% relative to the average) and northern rockfish (up 116% relative to the average). Since most rockfish species are very patchily distributed, the survey estimates are very imprecise. Hence model estimates leading to ABC recommendations were significantly moderated. For Pacific ocean perch, the 2006 ABC increased by 5% to 14,261 t. For northern rockfish, the Council was presented with an array of models implementing a variety of new data.

Further analyses were recommended and for precautionary reasons, the Council opted to keep the ABC the same as the 2005 level (5,091 t). For rougheye rockfish using a model introduced last year, the 2006 ABC dropped 2% to 983 t while the shortraker rockfish ABC was up 12% from last year to 843 t. Other slope rockfish (an assemblage of which 92% are silvergrey, sharpchin, redstripe, and harlequin rockfish) 2006 ABC increased 6% to 4,152 t.

The pelagic shelf rockfish assemblage, 90% of which comprises dusky rockfish, 2006 ABC increased 19% to 5,436 t. Demersal shelf rockfish (comprising mainly yelloweye rockfish) 2006 ABC remained the same at 410 t. Shortspine thornyheads biomass levels are stable or increasing slightly. The 2005 survey estimate dropped by 7% for shortspine thornyheads but the overall biomass is still 55% higher than the average level since 1984. This results in a 14% increase for the 2006 ABC (based on the average of the two most recent surveys) to 2,209 t. This compares to a 2005 shortspine thornyhead catch level of 720 t.


GOA Atka Mackerel:  The 2005 bottom trawl survey had a number of stations that contained significant quantities of Atka mackerel and the highly uncertain (CV = 50%) biomass estimate was up 65,500 t in 2003 to 100,900 t. Currently no directed fishing for Atka mackerel is allowed in the GOA due to Steller sea lion protection measures. The Council set the 2006 ABC to 4,700 and the TAC to 1,500 t (sufficient for bycatch needs in other fisheries).


GOA Skates:  The updated assessment used the most recent survey data for ABC and OFL recommendations. Other significant findings in this year’s analysis were that skate catch estimates from the halibut fishery are larger than had previously been estimated. This heightened the concern of fishery development potentials for these stocks, particularly given that survey estimates suggest stable to slightly declining trends.

The Plan Team and the Council continued to support conservation measures where “big” and “longnose” skate species are managed separately from the aggregate complex known as “skates” since these have been the target of developing fisheries in recent years. The less sought-after “other” skates (combined Bathyraja spp.) complex is managed separately as a third category within this assemblage.

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AFSC Quarterly
Research Reports Oct-Dec 2005