Some fragile stocks in the ocean, including cod and flounder, could be rebuilt using fish hatched in captivity and released into the wild, according to a new study by the University of New Hampshire.

While the study, which ran from 2001 until 2006, only used winter flounder eggs from wild fish and hatched in captivity in Newcastle, N.H., Elizabeth Fairchild, the postdoctoral research associate at UNH in charge of the study, said it could be good news for fishermen because it could be a model for other stocks, such as cod or haddock.

Catching those species is heavily restricted because of past overfishing, but they are popular with fishermen and consumers.

"It's a scientifically based program to determine the steps to take if you wanted to stock winter flounder so we could turn over this technology to managers or agencies to use," she said.

The study focused on the winter flounder because they do not migrate. They stay around estuaries, semi-enclosed coastal waters with at least one river flowing into them, such as the area off Annisquam or in Essex Bay. Also, the hatchery techniques for them are well-developed.

Fairchild said the study, called "The Science Consortium for Ocean Replenishment," had three main goals:

* refining hatchery techniques to produce the healthiest fish;

* figuring out release strategy, or where, when and how to release the fish;

* assessing the impact these released fish have on the ocean.

Hatcheries have been around for at least 100 years. Locally, fish were once hatched and released off Ten Pound Island, said Vito Calomo, executive director of the Massachusetts Fishery Recovery Commission. Traditionally, though, stocking occurs in freshwater sources, such as rivers, lakes and ponds.

"Marine stock enhancement is not a new science," Fairchild said. "The U.S. government tried stocking fish at the turn of the (20th) century, but none of the fish were marked, so you couldn't determine if it was successful."

Hatcheries are not new to the area, either. The state used to run a hatchery on Martha's Vineyard that grew and released lobsters, but that facility is empty and its success is unknown because the lobsters were not tagged, said David Pierce, deputy director of the Massachusetts Division of Marine Fisheries and a member of the New England Fishery Management Council.

"We were never able to document whether stocking had an impact," Pierce said.

Currently, there are no efforts at the state level to start any kind of hatch-and-release program.

However, for such a program to have a real impact in the ocean, millions of young fish would have to be released into the wild, Fairchild said. The largest amount released during her study was 20,000 and the average each year was "a couple thousand."

"You'd have to scale everything up," she said. "And you'd have to monitor fish health much closer. As they're more densely stocked, there's more possibility of them becoming sick or stressed."

While the hatch and release phase of the study is complete, Fairchild said they still intend to monitor the coastal waters and the health of all the winter flounder in the area to make sure the releases are, at the very least, harmless to the wild-hatched stock.

"We haven't seen any negative problems," she said.

The fish for the study are hatched in the UNH facility in Newcastle and raised for one year, when they are about the size of a potato chip. During their time in the tank, the fish are kept to a specific density to prevent disease and parasites.

The trickiest part is to get the young fish, called fry, to respond to a predator as if they had been raised in the wild.

One technique is to toss a crab in the tank and have it eat a fish while the others watch. Another is to put in a mock-up of a predator hooked to an electric current. When the fry get too close, they get a mild jolt.

When they are large enough, the fish are transported to cages in the ocean, where they can acclimate to the natural ocean water, adjust to the color and light and learn to forage for food. After a few days, they are taken out and released.

Fairchild said they are careful to watch for disease, genetic defects and that the gender ratio of the fish being released is very close to the ratio found in the wild.

Pierce said the Division of Marine Fisheries will study the UNH report to see if the program is something that could be used in Massachusetts coastal waters to restock popular species and possibly earn a loosening of federal regulations on catch size and time at sea.

One impediment to creating a state program, or a private program encouraged by state aid and grants, is the large cost of starting a facility large enough to raise and transport enough fish for release. Calomo hopes that a public-private initiative could help fishermen with few days allowed at sea who lease their boats and time for other projects at sea.

Scientists "usually use fishermen who know how to use the gear and the nets," Calomo said. "They have the boats and when they don't have the days at sea, they lease their boats with a captain and crew."

Landings of winter flounder, often sold as flounder or lemon sole, are on the decline. In the 1980s, commercial fishermen landed about 20,000 metric tons a year, but now catch only about 600 metric tons annually, said Fairchild.

UNH flounder hatch-and-release study

Study's goals:

* Refining hatchery techniques to produce the healthiest fish.

* Figuring out release strategy, or where, when and how to release the fish.

* Assessing the impact these released fish have on the ocean.

Study's findings:

* Tagged winter flounder released at about 1 year of age have survived and are good candidates for hatch and release.

* Young flounder can be taught to avoid predators by watching a crab eat a fish, or with a dummy predator that gives a small jolt when the fish get near it.

Implications:

* Hatch and release could be used to restock depressed species if the program were larger in scale.

* Though winter flounder were used, other regulated groundfish species, such as cod or haddock, could be used as well.