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Fish answering the call for food may catch themselves

BOSTON — Call them Pavlov's fish: Scientists are testing a plan to train fish to catch themselves by swimming into a net when they hear a tone that signals feeding time.

If it works, the system could eventually allow black sea bass to be released into the open ocean, where they would grow to market size, then swim into an underwater cage to be harvested when they hear the signal.

"It sounds crazy, but it's real," said Simon Miner, a research assistant at the Marine Biological Laboratory at Woods Hole, which received a $270,000 grant for the project from the National Oceanic and Atmospheric Administration.

Miner said the specially trained fish could someday be used to bolster the depleted black sea bass stock. Farmed fish might become better acclimated to the wild if they can be called back for food every few days.

The bigger goal is to defray the costs of fish farming. If fish can be trained to return to the farmer after feeding in the open ocean for several days, farms could save money on feed and reduce the amount of fish waste released in concentrated areas.

The key question for fish farmers: How many fish will actually return, and how many will be lost to predators or swim away?

Randy MacMillan, president of the National Aquaculture Association, said fish farmers won't be easily convinced to adopt open-ocean ranching.

Previous experiments have used sound to train a fish to feed — similar to how Russian physiologist Ivan Pavlov famously trained dogs to salivate at the sound of a bell, expecting food.

But no one has ever tried to get fish to leave and return to an enclosure where they can be scooped up.

The project began last summer using 6,500 black sea bass. Miner said the first objective was to see if the fish could truly be trained. He kept the fish in a circular tank and sounded a tone before dropping food in an enclosed "feeding zone." Eventually, whenever the tone sounded, he had "remote-control fish," Miner said.

Miner is now trying to figure out how long the fish remember to associate the tone with food. So far, he's found that some fish forget after five days and others remember as long as 10.

By May, researchers hope to bring the experiment and about 5,000 black sea bass to a feeding station anchored in Buzzards Bay.

MacMillan is not convinced the fish won't just swim away. He also expects large numbers of released fish to be lost to predators.

Miner said real answers won't start coming until this spring. "There's probably 18,000 ways for it to go wrong and only one way to go right."

Fish answering the call for food may catch themselves 03/26/08 [Last modified: Thursday, March 27, 2008 10:37am]
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