Boston — For years American fishermen watched as large Soviet trawlers swept with vacuum-cleanerlike efficiency through New England's richest fishing grounds. Then when Congress in 1977 restricted foreign fishing within 200 miles of the United States coast - effectively excluding the Soviets and others - US fishers apparently took up where the Russians left off. They nearly dealt a fatal blow to fish stocks - particularly haddock - that were once the mainstay of the New England fishing industry.
Today, concerned fishermen and government representatives are working together to help boost depleted fish populations in New England waters and to ensure that the overfishing of the 1970s is not repeated in the 1980s.
''Haddock used to be the backbone of the fishing industry,'' says Guy Marchesseault, executive director of the New England Fisheries Management Council. He says the average annual catch between 1930 and 1960 exceeded 50,000 metric tons. But by the early '70s the haddock catch had declined to about 6,000 metric tons.
He notes that the haddock population bounced back in the late '70s, but ''now , landings of haddock have been going down since 1980.''
''The haddock is in very bad shape,'' adds Richard Seamans of the National Marine Fisheries Service. ''It did come back fairly well, but then the US fishing industry knocked it back down.''
Federal statistics tell the story. In 1965, New England fishers caught 134 million pounds of haddock. By 1976, the catch was down to 12 million pounds. The catch rebounded to 55 million pounds in 1980, only to fall again to 32 million pounds last year.
Experts say it is still too early to tell whether the haddock is on the rebound.
The New England Fisheries Management Council is developing a comprehensive management plan to be implemented in 1985 for New England fishing grounds. The plan is expected to examine the effects of any proposed actions or regulations on all species of fish in New England waters.
In the meantime, an interim fishing management plan has been in effect since 1982. The current plan is aimed primarily at managing the stocks of the three main moneymaking fish in local waters - haddock, cod, and flounder.
The plan requires fishermen to throw back any cod or haddock shorter than 17 inches or any flounder under 11 inches. It also outlaws use of fish nets with a mesh smaller than 5 1/2 inches. In addition, the plan forbids fishing in two designated spawning areas for three months each spring.
The area of the study and management plan includes all New England waters, but it is aimed specifically at Georges Bank. Extending approximately 200 miles to the east and south of Cape Cod, Georges Bank is widely acknowledged to be among the most productive fishing grounds in the world.
That is one of the reasons that Soviet, Polish, Japanese, and other foreign trawlers were attracted to Massachusetts waters in the late '60s and early '70s.
According to fishing industry sources, the foreign fishermen practiced ''pulse fishing,'' in which one species of fish is pursued until the fish population drops so much that it's no longer economical to fish for the species. Then they moved on to a different species. They are said to have used large nets with tighter mesh that tend to catch the smaller, young fish as well as the adult fish.
Following the 1976 passage of the 200-mile limit, New England fishermen made substantial investments in new boats and modern equipment. The fishermen were banking on the hope that fishing profits would go up, since they no longer had to compete with Soviet and other foreign fishermen.
''The 200-mile limit brought probably the most dramatic change to the fishing industry since the changeover from sail to steam,'' says Mr. Seamans.
A temporary quota system was put on fish catches, aimed at helping fish stocks rebound from overfishing. But the many new fishing vessels, along with older boats refitted with more modern equipment, managed to knock some fish stocks back down.
The quota system, which fishers objected to, was eventually replaced with the current fish management regulations.