The Environmental Protection Agency, responding to pleas from Alaskan seafood processors and some powerful senators, suspended regulations for the 1980 fish processing season that could have closed down salmon canning facilities in five of Alaska's bigger cities.

The regulations, first established three years ago, require processors to screen out larger pieces of fish by-products from the waste pumped directly from their plants through pipes into neighboring seas. Under the EPA requirement, the larger fish pieces were to be collected and taken by barge and dumped further out at sea. In pre-EPA days, the plant waste -- fish heads and all -- went right into the water.

Since 1977, the processors have balked at putting in the required screens and hiring the barges, claiming the regulation would add $1 million to the cost of each plant's operation. They also argued that throwing biodegradable fish waste into the sea isn't quite the same as putting chemicals there.

EPA didn't agree, and the matter went to court, with the federal agency threatening to fine the salmon plants for every day the unscreened fish waste goes into the water.

Last month, however, EPA changed its mind, apparently by a meeting EPA Director Douglas Costle had with the Alaska processors and Sens. Warren Magnuson (D-Wash), Henry Jackson (D-Wash.) and Ted Stevens (R-Alaska).

EPA's decision to suspend the regulations, reported in the Federal Register, was based in part on the financial damage to the Alaskan economy that would result from a shutdown of the processing plants in the face of this season's expected record catch. In a normal year, the value of processed salmon for the state exceeds $400 million.

EPA said it will take another look at the cost of equipment needed to meet the proposed EPA regulations, compared with the public benefits to be gained.