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Tagging project might help reveal where halibut spend the winter

Posted: Monday, November 27, 2000

SOLDOTNA (AP) -- A small, electronics-packed bobber that one day may help unlock the mysterious ocean life of salmon is being tested right now on seven Resurrection Bay halibut.

The halibut are big -- the largest is 100 pounds -- and well-suited to the prototype devices, 3-inch-long tags that look like snagged fishing lures attached to a halibut's back by a tungsten wire.

''The halibut were just a species of choice. One, because they're large and, two, they were readily captured and seemed amenable to a period of time in captivity,'' said lead researcher Jennifer Nielsen, supervisor of fisheries research for the biological resource division of the U.S. Geological Survey.

Inside the cigar-shaped tag, topped with a 2-inch, air-filled ball, is a digital memory card and sensors constantly recording water pressure, light and temperature.

The devices are programmed to corrode their tungsten wires with acid on June 15 and float to the surface, where they will begin transmitting their stored information to passing satellites.

Assuming everything works right, scientists can use the stored data to interpret where the halibut have been swimming all winter, Nielsen said.

Sunrise and sunset provide the longitude, while temperature and depth data suggest a fish's latitude. Accuracy is limited to a 40-nautical-mile range. That's imprecise, she said, but a more accurate locator, the global positioning system, doesn't work under water.

Five of the tagged halibut were released a week ago in Resurrection Bay. Two others were left behind at the Alaska SeaLife Center in Seward, partly so Nielsen can watch how the fish cope with their tags but also so the center can display the surprisingly lively halibut to visitors.

The flat-bodied fish adapted quickly in the month they were in captivity at the sea life center. They were being hand-fed within a week and were swimming to the surface of the center's holding pond to check things out.

The $77,000 project, funded by the Exxon Valdez Oil Spill Trustee Council, is one of nine ongoing research projects at the center.

While the project is really to test the tags, Nielsen hopes to learn a little about halibut behavior over the next eight months. For instance, will the halibut stick around, or will they migrate? If so, how far? ''Some people say fish caught off California come from Alaska. We will be able to document any large ocean migrations these fish might perform,'' she said.

While the tags been used on other large fish species, such as tuna and marlin nearer the equator, this is the first test so far north.

The ultimate goal is to test this relatively new technology so it can be used in other studies, whether it is halibut, ling cod or king salmon, she said.

(Distributed by The Associated Press)



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