Environmental groups have decided they’re tired of waiting for a federal agency to implement an overdue plan to protect dwindling populations of false killer whales in Hawaiian waters.

Earthjustice, representing the Center for Biological Diversity and Turtle Island Restoration Network, filed a lawsuit Monday against the National Marine Fisheries Service and U.S. Department of Commerce.

NMFS is six months past its statutory deadline to finalize a proposed rule that would protect the species, a type of dolphin that got its name because it looks like an orca.

False killer whales are dying at an unsustainable rate due to longline fishermen accidentally catching them while hunting tuna and other fish. Unless things change soon, the species will go extinct, according to federal scientists and environmental groups.

The proposed plan calls for using weak hooks, which would let bigger animals break free while retaining the targeted fish. The plan also proposes permanently closing certain areas nearer to shore where one group of false killer whales is down to the last 170 animals, Earthjustice attorney David Henkin said.

“The tuna longline fishery is killing them at three times the rate they can sustain,” he said. “Another group of false killer whales is being depleted by the fishery at four times the rate they can sustain. We’re taking action to protect these false killer whales before they’re gone.”

NMFS put the proposed rule out for public comment in October, triggering a Dec. 16 deadline for implementation. The Western Pacific Regional Fishery Management Council, which advises NMFS, offered lengthy written testimony against the plan unless certain conditions were met and a more detailed analysis of its impact on the fishing industry was done.

NMFS Regional Administrator Michael Tosatto’s April 26 letter to Earthjustice, which was checking on the status of the final rule, reflects the need to address some of Wespac’s concerns before implementation.

Tosatto said in the letter that the plan would be implemented “in the near future” after additional research and analysis.

“While we agree that the conservation needs of false killer whales are of paramount concern, we are also mindful that our final rule must be supported by the best available scientific and commercial information,” he said.

Henkin said NMFS can fine-tune the rule after it’s implemented.

“We were left with the firm conviction that absent a lawsuit, the agency was not going to implement anything anytime soon,” Henkin said. “If the people in the know say, ‘No problem, it’s about to come out,’ we’re willing to give the agency a little slack. We don’t take lightly going to court. But we had to say enough already.”

Earthjustice first sued NMFS over this issue in 2003. That prompted the agency to classify the Hawaii longline fisheries as “Category I” based on the industry’s impact on the level of injuries and deaths of false killer whales.

That should have prompted NMFS to form a team to develop a plan to address the issue, but that didn’t happen until Earthjustice sued again.

In January 2010, NMFS established what’s called a take reduction team, which is comprised of scientists, environmentalists, government officials and fishing industry representatives.

The diverse team agreed on a draft plan six months later, which formed the basis of the proposed rule NMFS has since failed to implement. (Wespac Executive Director Kitty Simonds submitted testimony to NMFS that says some key conditions upon which the draft plan came to consensus were compromised, and the proposed plan thereby undermined the team’s process.)

A spokeswoman for NOAA, which NMFS falls under, said Monday afternoon that officials had just received the lawsuit and were unable to comment.

A message seeking comment from the Hawaii Longline Association was not returned by Monday evening.

Here’s the complaint that was filed in U.S. district court Monday: