A 1998 biological study by the NMFS is outdated, thin on substance and contains "no meaningful analysis" of the effect that commercial harvests have on the sea lions' critical habitat, a step required by the Endangered Species Act, the judge said in the opinion issued on Tuesday.

The biological study "is limited in scope, heavy on general background information, and deficient in focused and meaningful discussion and analysis of how these large fisheries, and the complex management measures which regulate them, affect endangered Steller sea lions," Zilly said.

He issued a summary judgment sought by the plaintiffs - Greenpeace, the American Oceans Campaign and the Sierra Club - that orders NMFS to re-do its study of how commercial fisheries are affecting the endangered sea mammals.

In July, Zilly issued a similar ruling that criticised an earlier biological study conducted by NMFS. But it led to no immediate policy changes by the agency.

GREENPEACE PLEASED BY RULING

Environmentalists who sued NMFS over the sea lion policies hailed Zilly's ruling.

"Greenpeace has long been sceptical of NMFS's repeated concessions to the industrial trawl fleet; now the court has shown that we were not mistaken," Paul Clarke of Greenpeace said in a news release.

Steller sea lions have been disappearing from the rocky coastlines of western Alaska over the past two decades, the same period during which the commercial pollock harvest has blossomed.

The western Alaska population, from eastern Prince William Sound to the the tip of the Aleutian Islands, is down to about 20,000 from 120,000 in the late 1970s.

NMFS declared the western Alaska Steller sea lion threatened in 1990 and endangered in 1997; scientists say the mammals are slowly staving.

Alaskan pollock, a low-priced whitefish, is sold in fillets and as a paste that forms imitation crabmeat and other food products.

The pollock catch in the Bering Sea and Gulf of Alaska is the nation's largest commercial seafood harvest. Other groundfish species, such as Pacific cod and black cod, are also fished commercially in the same waters.

RULING'S EFFECT UNCLEAR

Zilly's ruling came as participants in the lawsuit - environmentalists, agency officials and industry representatives - were set to meet for a mediation session in Seattle. The session was ordered by the judge in an attempt to reach a settlement in the case.

It was unclear on Thursday whether the ruling will force a cut to this year's harvest, already underway, said participants in the case.

"That's something that we'll be reviewing carefully with the plaintiffs and watching to see if NMFS makes any modifications," said Eric Jorgenson, an attorney with Earthjustice Legal Defence Fund, one of the groups representing the plaintiffs.

Jim Gilmore, director of public affairs for the Seattle-based At-Sea Processors Association, also said he is unsure of the ruling's effects.

"It really is a procedural issue at this point," he said.

But his group, an association of factory trawlers that intervened in the case, fears that harvest reductions may result if the plaintiffs push the issue.