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FIT Research Projects:Aleutian Islands Cooperative Acoustic Survey Study

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  Walleye pollock
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In 1990 Stellar sea lions (Eumetopias jubatus) were listed as “threatened” under the Endangered Species Act (ESA). Directed pollock fishing in the Aleutian Islands was closed beginning in 1999, in part due to concerns about Steller sea lions. Under Steller sea lion mitigation measures adopted by the North Pacific Fishery Management Council (NPFMC) in 2001, NMFS reopened pollock fishing restricted to those areas outside critical habitat (generally as 20 miles from rookeries and haulouts listed in table 4 of CFR 679.50) beginning in 2003. The June 2003 supplement (pg. 30 & 31) to the 2001 biological opinion describes experiments on fisheries effects on prey availability for Steller sea lions and the need for further studies to determine whether commercial fishing activities impact the prey availability of pollock to Steller sea lions.

Section 803(a-d) of PL 108-199 (page 110) allocated the directed pollock fishery in the Aleutian Islands to the Aleut Corporation. The allocation was implemented under Amendment 82 to the Bering Sea/Aleutian Islands Fishery Management Plan by the NPFMC, and became effective in 2005. Until the regulations implementing the Aleut Corporation allocation were in effect in 2005, NPFMC recommended pollock Total Allowable Catches (TACs) that were insufficient to support a directed fishery. Beginning in 2005 the Aleutian Island pollock TAC was set at 19,400 metric tons, however directed pollock harvests in 2005 were less than 200 metric tons.

In March-April 2006 the first Aleutian Islands cooperative acoustic survey study (AICASS) was conducted (Fig 1).  These surveys were part of a cooperative project between NMFS, the Aleut Corporation, the owners and operators of the F/V Muir Milach, and Adak Fisheries LLC to test the feasibility of using small (<35 m) commercial fishing vessels to conduct acoustic surveys on Alaska walleye pollock in the central Aleutian Islands. To verify the acoustic data and to support the study, 1,000 t of walleye pollock was allocated to be harvested within Steller sea lion critical habitat. The acoustic and biological information from the study will be used to assess:

1) if it is feasible to conduct acoustic surveys in the Aleutian Islands using commercial fishing vessels,

2) if the data collected are of sufficient quality for management purposes, and

3) the extent that fine scale spatial and temporal management measures may be biologically reasonable.

study site




Fig. 1 Study area for 2006 cooperative acoustic survey. The shaded areas are Steller sea lion critical habitat.  The boxed areas are where the acoustic survey transects were located.  The large area and small areas were each surveyed three times







A total of six acoustic surveys were successfully completed resulting in precise estimates of pollock biomass in the surveyed areas over time. The abundance trend was stable for the first two surveys, and then declined significantly during the final four surveys. During the study 965 t of groundfish were harvested, 97% of the harvested groundfish were removed from a 72 nm2 area in the center of the study area and 85% of the harvest occurred in the final 11 days of the study. Distribution and abundance of pollock, although dynamic in the overall survey area, did remain stable during the times when, and in the areas where there were lower densities of pollock and lower fishing effort during the survey. Further analyses are needed to evaluate the cause of the decline in the fished area. The scientific objectives of the 2006 AICASS were achieved. The project also fostered an excellent working relationship among NMFS, the Aleut Enterprise Corporation, and the fishing industry. Local participation and stakeholder involvement enhances NMFS ability to provide responsible stewardship of this important marine resource.

A second AICASS was conducted during March-April 2007 (Fig._2).  Two surveys covering a broader area were successfully completed.  Data are currently being analyzed. 

transect site




Fig. 2. Study area for 2006 cooperative acoustic survey.  Heavy lines are the acoustic transects.  Shaded areas are Steller sea lion critical habitat.  The 200m depth contour is also shown.








For more details on the results summarized above, see the documents below, or contact Steve Barbeaux ( or 1-206-526-4211). 



Barbeaux, S. in prep. Aleutian Islands Cooperative Acoustic Survey Study 2006.  NOAA Tech. Memo. 

A cooperative pollock acoustic biomass survey for management of fisheries interactions with Steller sea lions in the Aleutian Islands (NPRB project 730)  



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