ALBUQUERQUE, N.M. — Two environmental activist groups have filed suit in federal court here to force the U.S. Department of Interior to protect a two-inch minnow in the Canadian River that winds across eastern New Mexico, the Texas Panhandle and Oklahoma.

The Sierra Club and the Southwest Center for Biodiversity this week filed suit to force the U.S. Fish and Wildlife Service to protect the Arkansas River Shiner, a silvery minnow that was once abundant in the Arkansas River and its tributaries. According to Oklahoma researchers, the fish has disappeared from 80 percent of its historic range and is now found chiefly in the Canadian and South Canadian Rivers in Oklahoma, Texas and New Mexico.

In their suit, the activists demand restrictions on the use of groundwater from the Ogallala Aquifer, a vast underground aquifer stretching from the Texas South Plains north into Nebraska.

The U.S. Fish and Wildlife Service proposed listing the shiner as an endangered species in 1994. Congress imposed a moratorium on such listings, but the moratorium was lifted in April 1996. USFWS was expected to make a final decision on listing the shiner by April 30, 1997, but under an agreement with Texas and Oklahoma wildlife agencies, the federals may list the shiner as "threatened" instead of "endangered."

A spokesman for the Lone Star Chapter of the Sierra Club claims the agreement, a memorandum of understanding that relies on voluntary steps by the states, isn't enough to ensure the minnow would be protected.

The Fish and Wildlife Service took additional comments on listing the shiner earlier this year. Ken Collins with the U.S. Fish and Wildlife Service field office in Tulsa said earlier a decision should be made by this summer.