July 09, 2007
Monday

Three vessels chartered by NOAA's Alaska Fisheries Science Center are engaged in more than two months of scientific bottom trawl surveys in the Gulf of Alaska, continuing data-gathering that has gone on every two or three years since 1984.

Scientists on the Sea Storm, the Gladiator, and the Vesteraalen are expected to complete about 825 survey trawl hauls over a 75-day period along the continental shelf and upper continental slope of the Gulf of Alaska. They started May 25 in Dutch Harbor and are expected to end their charters around August 7 in Ketchikan. The data are used to help determine future management decisions regarding fishing activities in the Gulf of Alaska.

"This biennial survey tells us trends in the distribution and abundance of important groundfish species such as walleye pollock, Pacific cod, flatfish, and rockfish," said Alaska Fisheries Science Center's Resource Assessment and Conservation Engineering Division Director Russ Nelson. "It also helps us measure various biological and environmental parameters such as sea surface and bottom temperatures and the size, age, and food habits of important groundfish."

The three boats started the survey near the Islands of Four Mountains, about 180 miles southwest of Dutch Harbor, and will work their way eastward to the U.S.-Canada border at Dixon Entrance. The crews of all three vessels will take on-shore breaks in Sand Point, Kodiak, and Seward.

Each of the vessels is identified with clearly visible "NOAA Research" placards.

Of particular note is the operation of these vessels in southeast Alaska, a region where trawl vessels are not typically seen, between late July and early August.

Each vessel will make 15-minute trawl hauls at specific, randomly pre-selected stations. Researchers sort, weigh, and enumerate by species each trawl catch. They collect samples from selected species to determine fish size and age, sexual maturity, and food habits. Data on the temperature of the ocean and depth of the survey tows are recorded using a 'bathythermograph' attached to the trawl headrope. Sample depths will range from depths greater than 15 meters near shore to 1,000 meters on the continental slope.

Following completion of the survey in early August, scientists will edit and finalize the data they collected on fishing effort, catch rates, and fish size distribution and generate fishery-independent estimates of geographic and depth distribution, abundance, and population size composition by the end of September. Stock assessment modelers will then combine that information with data from the fishery and results of previous surveys to update the stock assessments used by the North Pacific Fishery Management Council to manage the groundfish stocks of the Gulf of Alaska.

Each of the three boats holds six researchers plus the skipper and crew. Participating researchers are from the Alaska Fisheries Science Center, the California Academy of Sciences, the International Pacific Halibut Commission, the University of Washington, the Alaska Sea Life Center, and the University of Alaska, Fairbanks.

The survey has been carried out every other year since 1999. Before then, it was every three years, starting in 1984.

Source of News:

NOAA Fisheries Service in Alaska
www.afsc.noaa.gov.

 

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