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Auke Bay Laboratories (ABL)

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Oct-Nov-Dec 2011
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Marine Ecology & Stock Assessment Program

Groundfish Stock Assessments

This quarter, scientists from ABL's Marine Ecology and Stock Assessment (MESA) program completed nine full stock assessments and two updated assessments for 11 species/species groups of Alaska groundfish. Full assessments included Alaska sablefish, Gulf of Alaska sharks, and the following assessments for Gulf of Alaska rockfish: Pacific ocean perch, thornyheads, northern rockfish, dusky rockfish, rougheye/blackspotted rockfish, shortraker rockfish, and "other rockfish." Short stock assessment updates included Alaska grenadiers and Being Sea/Aleutian Islands sharks.

Substantial changes and improvements were made to the assessments for northern rockfish and what was previously the pelagic shelf rockfish management complex. The pelagic shelf rockfish complex was dissolved, and dusky rockfish (the complex's dominant species) is now its own assessment chapter, while the other two pelagic shelf species (yellowtail and widow rockfish) were combined with the previous "other slope rockfish" complex and renamed simply "Gulf of Alaska other rockfish."

A stock structure analysis was completed for dusky rockfish, and it was determined that the structure was reasonably consistent with current management units. In addition, Gulf of Alaska shortraker rockfish is now a separate assessment chapter, having been removed from the "Gulf of Alaska shortraker and other slope rockfish" chapter.

The northern and dusky rockfish models were both updated with new maturity data, using a novel approach that combined multiple maturity data sets and accounted for uncertainty within the model. For northern rockfish, an extensive analysis was conducted to examine the best way to choose the number of bins used in analyzing age composition data. As a result, the age-composition bin structure was increased by 10 years, resulting in an improved fit to the data.

For dusky rockfish, different selectivity patterns yielded similar fits to the data with far fewer parameters. The Alaska sablefish stock assessment model was unchanged from 2010 and showed a modest increase in Total Allowable Catch (TAC) recommendations as a result of 2 years of relatively high longline survey abundance estimates.

Stock Assessment and Fishery Evaluation (SAFE) reports or executive summaries were prepared for each assessment, and results were presented to the North Pacific Fishery Management Council'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 TAC) for these species in 2012.

For more information about these assessments, see the Status of Stocks & Multispecies Assessment Program's article "Groundfish Stock Assessment for 2012: Fishery Quota Recommendations" in the Resource Ecology and Fishery Management (REFM) Division section of this issue or the full stock assessment reports on the AFSC website at

By Dana Hanselman

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