PHOENIX — Five environmental groups filed a lawsuit against the federal government Thursday, saying it has failed to protect endangered fish in the Colorado River.

Because of the failure of the Interior Department and its Bureau of Reclamation to provide a more natural environment in the river, the humpback chub, razorback sucker, Colorado pikeminnow and bonytail chub are in danger of extinction, the suit alleges.

The suit, filed in U.S. District Court in Arizona, contends the government is violating federal law by operating Glen Canyon Dam in a manner that fails to protect the features of Grand Canyon National Park and Glen Canyon National Recreation Area.

The dam straddles the Arizona-Utah border, backing up the Colorado River to form Lake Powell. The suit contends the dam releases water at unnatural temperatures, quantity, quality and frequency, and deprives the Grand Canyon of sediment and needed nutrients.

The lawsuit asks the court to order Interior Secretary Gale Norton and the Reclamation Bureau to consult with the U.S. Fish and Wildlife Service over the effects of dam operations, and ultimately, provide a "more natural flow and water temperature regime" and "adequate downstream nutrients and sediment."

The species in the most danger is the humpback chub, the adult population of which declines between 15 percent and 20 percent each year, according to a 2005 report by the U.S. Geological Survey.

Currently, there are between 3,000 and 5,000 in the Colorado River, but that number could decline sharply to between 1,500 and 2,000 in the next 10 to 15 years if nothing is done.

"Arizona's native fish are overwhelmingly imperiled," said Robin Silver, conservation chair for the Center for Biological Diversity, one of the plaintiffs.

For years, officials have studied how to regulate the temperature of water released from the dam, said Barry Wirth, spokesman for the Bureau of Reclamation's Upper Colorado region. But change takes time, he said.

"There's a lot of things that come into play," he said. "We know the technology works. It's just not an off-the-shelf thing."

Wirth said programs such as reducing predators and water flow strategies help the humpback chub and other species.

Neither Wirth nor agency spokeswoman Trudy Harlow in Washington would comment directly on the lawsuit.

The suit was filed by the Center for Biological Diversity, Sierra Club, Glen Canyon Institute, Living Rivers and Arizona Wildlife Federation. It followed another legal battle last month between the federal government and two environmental groups, Grand Canyon Trust and Earthjustice.

In that case, U.S. District Judge Frederick Martone ruled the U.S. Fish and Wildlife Service recovery plan for the endangered fish was ineffective. He ordered a new plan to include more specific goals and a timeline for recovery.

Although the ruling was a victory for the environmental groups, a better recovery plan won't save the fish unless the government acts on it, Silver said.

"A recovery plan does not save species because they're never obeyed," he said. "It won't cause anything to happen."

Source: Associated Press