Earthjustice sued the National Marine Fisheries Service in federal court in Honolulu on Monday, saying the agency failed to complete and implement a plan to protect false killer whales from Hawaii’s longline fishing industry.

The nonprofit, public-interest environmental law firm said it filed suit to end "the continuing slaughter of false killer whales in the waters of Hawaii."

Wende Goo, a spokeswoman for the fisheries service, said Monday that officials had not had a chance to review the suit.

Earthjustice said the fisheries service’s own studies show that longline fishing is killing Hawaii’s false killer whales — a species of large dolphins — at three times the rate than the animals’ population can sustain, yet the agency is six months past its statutory deadline to finalize a plan to reduce the killing, called a take reduction plan.

False killer whales typically drown when they are hooked by deep-set fishing lines, which target ahi, Earthjustice said.

False killer whales that escape often trail fishing gear that hinders their ability to feed, causing them to die of starvation or infections stemming from their wounds, Earthjustice said.

"These magnificent false killer whales don’t deserve a cruel death at the end of a longline hook, especially since common-sense solutions already exist to prevent serious injuries and drowning," Todd Steiner, biologist and executive director of the Turtle Island Restoration Network, said in a statement. "The ecological cost of longlining is mounting. In addition to imperiled false killer whales, the fishery kills critically endangered sea turtles, albatrosses and other seabirds."

There are about 170 false killer whales within 87 miles of the main Hawaiian Islands and their population has been declining at a rate of about 9 percent per year since 1989, prompting the fisheries service to call for them to be listed as endangered under the Endangered Species Act, Earthjustice said.

Congress amended the Marine Mammal Protection Act in 1994, with the goal of achieving zero marine mammal deaths in commercial fisheries by 2001, Earthjustice said.

"Congress understood that time is of the essence if we are going to save marine mammals," Earthjustice attorney David Henkin said in a statement.