Scientists 'train' fish to catch themselves

Fish will one day be able to catch themselves if an experiment by US scientists proves successful.

Researchers at the Marine Biological Laboratory (MBL) at Wood's Hole, Massachusetts, are testing a plan to train fish to catch themselves by using a sound broadcast to attract them into a net.

They hope to release fish into the open ocean, where they would grow to market size, before enticing them into an underwater cage to be harvested when they hear a tone that signals feeding time.

If successful, the system could be used to bolster depleted fish stocks and reduce the costs of fish farming, scientists said.

"It sounds crazy, but it's real," said Simon Miner, a research assistant at MBL.

Mr Miner said the first step in the project was to establish whether fish could be trained.

Fish, including black sea bass, stout and bottom-dwelling fish, were kept in a circular tank and fed in an enclosed feeding area within the tank.

Scientists would sound a tone before they dropped food into the feeding area, which the fish could enter through a small opening.

The tone was played for 20 seconds, three times a day, for about two weeks. The result, according to Mr Miner, was "remote-control fish".

"You hit that button and they go into that area and they wait patiently," he said.

Mr Miner is now trying to determine how the fish remember to associate the sound with food.

He said the fish were fed outside the feeding zone for a few days, and then the tone was reinstated to see if they would return to the feeding area.

Some fish forgot after five days, while others remembered for as long as 10, Mr Miner said.

In May, scientists will expand the experiment by bringing about 5,000 black sea bass to a feeding station called an AquaDome in Buzzards Bay, 45 miles south-east of Boston.

The fish will be fed in a dome after a sound broadcast and, when sufficiently "trained", will eventually be freed.

Two days later researchers will then sound the tone to see if they return.

But fish farmers will take some convincing before they adopt this system.

"The commercial side is going to be sceptical," said Randy MacMillan, the president of the National Aquaculture Association in America.

"My experience with fish is they will wander far and wide," he added.