Arctic Science Journeys
Radio Script
1997

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Halibut Heave-Ho
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STORY: Off the coast of Alaska, dozens of commercial fishing vessels drag huge nets through schools of bottom-dwelling fish such as flounder, sole and cod. Their nets also scoop up large numbers of unwanted or prohibited fish. Last year, fishermen tossed 750 million pounds of such fish back into the sea.

Among the throw-backs were about 12 million pounds of halibut, worth about $35 million dollars. Until recently, no one knew how many of these fish would survive. Ellen Pikitch is a University of Washington fisheries professor looking for the answer.

PIKITCH: "There are two elements to halibut mortality. One is how many halibut are actually caught as bycatch. And then the second issue is how many of those that are caught die. And what my research has focused on is the second issue, and that is how do we reduce the mortality of halibut that are caught, how do we keep halibut alive?"

Professor Pikitch studied the factors that cause halibut to die. She says how long the fish are exposed on the deck of the vessel, the air temperature and the size of the fish all determine whether they'll survive once returned to the sea.

PIKITCH: "One of the things we really hadn't been thinking of before we did the study was the presence of sand or mud in the catch. We found that in some tows, where there was a lot of sand or mud in the catch, for those we found that the survival was very, very poor. It probably suffocated the fish."

Pikitch says such injured fish likely would die soon after being returned to the sea. But more surprising, she says, is halibut continued to die for several days following their release.

PIKITCH: "What we found after repeated studies was that it took about three days for all the mortality that we were going to see in these fish to express itself. And after three days, and between three and five days, and out to seven days we really saw no change in survival over that period of time."

The findings were based on studies of net-caught halibut that were put into large cages and returned to the sea floor. At first Pikitch wondered whether the cages themselves were killing the halibut. But a separate experiment in which 100 halibut were trapped in baited cages and held for several days saw no halibut deaths.

Pikitch says her study will help fishermen improve the chances of halibut survival. Such measures are in their best interest, because fishing seasons close when too many halibut are caught.

For Arctic Science Journeys, this is Debra Damron reporting from Fairbanks, Alaska.