This story started out as a press release, which was picked up not only by local agricultural newspapers, but The Baltimore Sun, as well. It was also published in MAES' quarterly newsletter. This version was published in Outlook, Volume 7, Number 10, November 9, 1992, the staff newsletter for the University of Maryland, College Park. A shortened version was published in College Park, the alumni magazine.

Training Fish Like Pavlov's Dogs

Striped bass aquaculture would be more productive and cost efficient if we could just call the fish over to one location for feeding, harvesting and the treatment of disease. Arthur N. Popper, professor and chair of Zoology, is studying how to do just that.

"What I want to do is straightforward," says Popper, who is determining if striped bass can hear. If they can, Popper will ascertain if they can be trained to respond to a particular sound in a specific way.

His experiment, supported by the Maryland Agricultural Experiment Station, is quite simple. First, he will play a three-to five-second pulse of sound underwater in a tank filled with striped bass. Immediately after the sound pulse, food will be dropped at a specific place in the tank. If the experiment is successful, the fish will learn that the sound is saying, "Come here, I'm about to feed you at this spot."

In other words, the fish will learn that when they hear a sound, they should go over to a particular spot and wait to be fed.

There are reports, Popper says, suggesting that other countries may already be using sound as a way to attract, feed, control and harvest aquacultured fish kept in large ponds or pens. If he is successful, this technique can be used in the United States as well.

Aquaculture is an important industry for Maryland. Estimates for 1992 indicate that approximately 440,000 pounds -- about $1.1 million worth -- of aquacultured striped bass will be sold.

Studies similar to Popper's, such as those being done on walleye and sturgeon by Paul Patrick of Ontario Hydro in Canada, have been quite successful. Much has been learned about the hearing of more than 50 species of fish; however, we know nothing about the hearing of striped bass.

Some of the research on other species has shown that these trained fish grow larger faster. "It's quite logical," Popper says. "The less you have to work to find your food, the better you are going to eat, and the faster you will grow." You can think of it this way: If you had to search your entire house for food, you'd probably eat less than you do now, with the convenience of your refrigerator or cupboard.

Normally, aquacultured fish are fed by scattering the food throughout the pond. The likelihood of the fish being in the proper place at the right time to get the food before it falls to the bottom (and potentially goes to waste) is not very high. However, if fish can be told where and when to find their food, they eat more, and less of the food is wasted.

This training will be helpful in harvesting the fish as well. "You can train fish to come to one spot to eat, but you could also at some time call them into the net and harvest them," Popper says.

It may even be possible to grow more than one kind of fish in a pond and separate them with sound. Ideally, "if you have two species to respond, you can train one species to respond to one sound, and the other to another sound," Popper says. The different species will respond only to the specific sound for which they were trained, making separating the different kinds of fish easier.