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Marine Ecology and Stock Asessment Program

Groundfish Stock Assessments

This quarter, scientists from ABL’s MESA Program completed three full stock assessments and five updated assessments for eight species/species groups of Alaska groundfish. Full assessments included Alaska sablefish, Bering Sea/Aleutian Islands sharks, and Gulf of Alaska sharks. Short stock assessment updates included Gulf of Alaska Pacific ocean perch, northern rockfish, rougheye/blackspotted rockfish, pelagic shelf rockfish, and shortraker rockfish and “other slope rockfish”. An unofficial full assessment was also done for Alaska grenadiers because in the future they may become managed species that will require a stock assessment.

For the rougheye/blackspotted rockfish assessment, a stock structure analysis was completed, and it was determined that the structure was reasonably consistent with current management units. A review of factors affecting sablefish recruitment was written and presented at the request of the North Pacific Fishery Management Council (NPFMC). Stock Assessment and Fishery Evaluation (SAFE) reports or executive summaries were prepared for each assessment, and results were presented to the NPFMC’s Groundfish Plan Teams in November and also reviewed by the Council’s Scientific and Statistical Committee in December. The Council used these assessments as the primary source for determining catch quotas (levels of Total Allowable Catch) for these species in 2011.

For detailed information about these assessments, see the Status of Stocks & Multispecies Assessment Program’s article “Groundfish Stock Assessment for 2011: Fishery Quota Recommendations” in the Resource Ecology and Fishery Management (REFM) Division section of this issue of the AFSC Quarterly Report.

By Dave Clausen

Estimation of Bycatch in the Halibut Fishery

The Pacific halibut longline fishery makes up an important part of the total fishing effort in the Gulf of Alaska and Bering Sea/Aleutian Islands regions. This fishery is managed separately from other groundfish fisheries by the International Pacific Halibut Commission (IPHC), and as such, the boats do not fall under the same fishery observer requirements as other groundfish vessels. Because of this lack of observer coverage, scientists have no knowledge of the quantities of other species that are caught and discarded (bycatch) in the halibut fishery; however, the reauthorized Magnuson-Stevens Fishery Conservation and Management Act requires that all sources of removals be accounted for in future stock assessments.

The NPFMC has approved the restructuring of observer coverage, which will include placing observers on much of the halibut fleet. These changes will not take effect until 2013, but it is necessary to have estimates of catch for current assessments and the ability to look at the historical bycatch in the halibut fishery. A working group was formed in January 2010 to explore methods to estimate bycatch of species such as sharks, skates, and Pacific cod in the unobserved halibut fishery. This working group is composed of scientists from the AFSC, NMFS Alaska Regional Office, IPHC, and Alaska Department of Fish and Game (ADF&G).

A variety of quantitative methods are under investigation by the working group. The IPHC conducts a longline survey each year, which covers much of the Gulf of Alaska and Bering Sea/Aleutian Islands. Efforts have been made in past stock assessments to account for bycatch in the halibut fishery, in some cases using vastly different approaches, but all using the survey data as a proxy for actual observer data. The two main questions are: how do you treat the survey data to make it accurately reflect commercial effort; and what is the best way to extrapolate the survey data to total commercial effort?

The working group has examined previously-used methods as well as developed new approaches. The NPFMC Groundfish Plan Teams reviewed the various methods presented by the working group, and the recommended method will be further reviewed by the NPFMC’s Scientific and Statistical Committee in February 2011. Catch estimates based on these methods are expected to be available for the 2011 assessment cycle.

By Cindy Tribuzio


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