Scientists are training fish to net themselves

BOSTON — 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 allow black sea bass to be released into the open ocean, where they would grow to market size and 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 (NOAA).

Miner said the 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 key questions for fish farmers: How many fish will return, how many will be lost to predators and how many will swim away?

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

Previous experiments have used sound to train fish to feed, similar to what Russian scientist Ivan Pavlov did with his famous dogs that salivated at the sound of a bell, expecting food.

In Japan, scientists have used sound to keep newly released farmed fish in certain areas, where they could be caught in traditional ways.

But no one has 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 be trained. He kept the fish in a circular tank and sounded a tone before he dropped food in an enclosed "feeding zone" within the tank that the fish could enter only through a small opening. Researchers played the tone for 20 seconds, three times a day, for about two weeks. Afterward, whenever the tone sounded, "you have remote-control fish," Miner said.

By May, researchers hope to bring about 5,000 black sea bass to a feeding station, an "AquaDome," that will be anchored to the ocean floor in Buzzards Bay, 45 miles southeast of Boston.

The sea bass will be fed in the dome after a tone sounds. After researchers think they've been sufficiently trained, they will be freed. A day or two later, scientists will sound the tone again and see how many bass return. They'll do the experiment again near summer's end.

Scott Lindell, the project leader, said losing fish is a concern. But the savings of using the trained fish and the AquaDome is potentially huge: Even if only half the fish come back after reaching market size, the operation would be more profitable than current methods.