The Swinomish Indian tribe in northwest Washington has moved to intervene in a lawsuit between Skagit Delta farmers and the National Marine Fisheries Service over maintaining a tidegate that keeps farmland dry.

The tribe stated in a court filing Thursday it supports NMFS’s position that prolonging the tidegate’s life for another 50 years will block potential fish habitat and jeopardize Puget Sound chinook salmon and killer whales.

Federal officials, however, don’t have as much on the line as the tribe and may not defend their decision as vigorously as the tribe, according to the motion to intervene.

“Salmon provides us with the proteins, fats, vitamins and minerals that we need to be a strong and healthy people,” Swinomish Indian Senate Chairman Steve Edwards said in a sworn declaration.

Skagit Delta tidegates swing shut at high tide to keep Puget Sound saltwater from inundating farm fields. There are more than 100 tidegates protecting the 70,000-acre delta. Many are more than a century old.

NMFS concluded replacing a storm-damaged tidegate at the mouth of No Name Slough would jeopardize the continued existence of salmon and killer whales throughout Puget Sound.

Without repairs, the tidegate will fail and allow about 200 acres of farmland to become fish habitat, according to NMFS.

Skagit County Dike District 12 can replace the tidegate if it converts at least 8.6 acres somewhere in the delta into fish habitat to make up for the damage caused by the tidegate’s extended life, according to NMFS.

The district has sued in U.S. District Court for Western Washington. The district claims NMFS has misapplied the Endangered Species Act. Converting land into fish habitat would cost millions, according to the district.

In seeking to intervene in the lawsuit, the Swinomish tribe, represented by Earthjustice, said it has a history of prodding federal agencies to take a harder look at tidegates.

Tidegates block large swaths of Skagit estuary habitat, according to the tribe.

“The lack of sufficient estuary habitat is a primary limiting factor in Skagit chinook salmon recovery,” the motion reads. “The loss of fish opportunities has strained the tribe’s cultural lifeline and diminished tribal members’ overall well being.”

Farmers began building dikes and tidegates in the 1860s to dry out the delta. NMFS’s position sets a precedent for other tidegate repairs and jeopardizes farming in one of Washington’s most productive agricultural regions.