By Chris Woodward, The Center Square

A federal judge has issued a preliminary injunction blocking a plan to build a water diversion pipeline in southwest Montana meant to aid Arctic grayling, a rare species of freshwater fish.

District Judge Donald W. Molloy issued the injunction this week in a lawsuit brought by Wilderness Watch and other environmental groups against the U.S. Fish & Wilderness Service and the Montana Department of Fish, Wildlife and Parks. The pipeline is meant to divert cold water to the indigenous fish population that’s dwindled in the Red Rock Lakes Wilderness area.

The Missoula-based Wilderness Watch argued the water diversion pipeline within the wilderness area is a “blatant violation of the Wilderness Act, which prohibits the agency from intentionally modifying Wilderness habitat.”

Molloy wrote in the injunction that “in light of the Wilderness Act’s strict requirements, the mere possibility that the proposed action may aid in Arctic grayling conservation is not enough to create necessity.”

Montana Trout Unlimited, a fish conservation group that supports the project, called the ruling “a blow to the grayling, the spirit of collaborative conservation and Wilderness character.”

“This delay and its proponents stand to have far greater negative impacts to this Wilderness ecosystem by risking the disappearance of one of the most unique and iconic species than the short and modest construction efforts implementing the project in a Wilderness area would entail,” the group said.