The listing, issued by the National Marine Fisheries Service last November, "will result in needless water and land-use restrictions on Washington farms, especially those located near rivers inhabited by salmon," the orcas' prime food source, the groups wrote in the lawsuit filed Monday.

"As a result, farmers could face fines and even imprisonment for the most basic farm practices should such actions allegedly disturb salmon," they wrote - a scenario environmentalists described as far-fetched, though deliberately harassing a protected species can carry a year in jail.

The groups' lawyers, Russell C. Brooks and Andrew C. Cook of the Pacific Legal Foundation, attempt to base their complaint against the fisheries service on a fine technical point: The three orca pods that live in Western Washington inland waters from late spring to early fall every year are a distinct population of a subspecies, the Northern Pacific resident orcas, which include orcas off Alaska and Russia. Under the Endangered Species Act, the lawyers argue, only a distinct population of a species - not a subspecies - can be listed.

So, they say, the fisheries service could list the entire subspecies of Northern Pacific resident orcas as endangered, but it can't list only the Puget Sound pods.

Environmentalists scoffed and called the reasoning circular. Patti Goldman, of the environmental law firm Earthjustice, said it boils down to saying that the Puget Sound orcas gave up their membership in the orca species when they were named part of the subspecies.

Logically, Goldman said, a "distinct population segment" of a subspecies is also a "distinct population segment" of a species. She also noted that in the Endangered Species Act itself, the definition of "species" includes "any subspecies of fish or wildlife or plants."

"Just because there are orcas elsewhere in the Pacific Ocean doesn't mean we're willing to live without them in Puget Sound," Goldman said.

Brooks called the rebuttal a good point, but a losing one based on the strict wording of the act.

He said his clients aren't anti-orca; they just want the fisheries service to follow the letter of the law.

"There are some folks that are just going to dismiss them as killer whale haters," Brooks said. "But this is a very important legal issue. Just because it involves a sympathetic species doesn't mean the legal question should be ignored."

Puget Sound's Southern resident orcas - which consist of the J, K and L pods, or families - are genetically and behaviorally distinct from other killer whales, all sides agree. The pods use their own language, mate only among themselves, eat salmon rather than seals and show a unique attachment to the region.

The three pods number 89 whales - down from historical levels of 140 or more in the last century, but up from a low of 79 in 2002. Their numbers have gone through three periods of decline since the late 1960s and early '70s, when dozens were captured for aquariums, with each decline followed by a slight rebound.

Pollution and a decline in prey are believed to be their biggest threats, though stress from whale-watch boats and underwater sonar tests by the Navy are also concerns.

The National Marine Fisheries Service initially refused to list the whales under the Endangered Species Act, finding that they were not distinct from other orcas around the world - a finding based on a classification of the species written in 1758. In 2002, eight environmental groups sued, and U.S. District Judge Robert Lasnik ordered the agency to reconsider, using updated science.

The fisheries service eventually agreed that the Puget Sound orcas needed protection, leading to the listing in November. A draft recovery plan is expected to be released for public review this summer.