Environmentalists are suing U.S. wildlife officials in a bid to force federal protections for a rare, freshwater fish in Montana’s upper Missouri River Basin that’s suffered due to climate change and other pressures.

The lawsuit over Arctic grayling was filed Monday in U.S. District Court in Montana. The legal challenge comes more than two years after federal officials rejected Endangered Species Act protections, citing a conservation plan intended to boost grayling populations.

The fish, which are related to salmon and known for their sail-like dorsal fin, can reach 30 inches in length and are prized by many anglers.

Attorneys for environmental groups Center for Biological Diversity and Western Watersheds Project say the conservation plan has failed to protect the fish from warming temperatures and water withdrawals from rivers by farmers.

MONTANA HUNTER WHO MISTOOK HUSKY PUP FOR WOLF TO FACE LEGAL CONSEQUENCES

Wildlife advocates petitioned federal officials to protect Arctic grayling in 1991. Officials determined in 1994 and again in 2010 that protections were needed, but they were never imposed because other species were given a higher priority.

Federal officials ruled in 2020 that protections weren’t needed. They said conservation efforts were working and had increased Arctic grayling numbers in Montana’s Big Hole River and its tributaries.

Critics of that decision said there has still not been enough water in the Big Hole during summer to sustain the fish.

A U.S. Fish and Wildlife Service representative did not immediately respond to the lawsuit.