*Editor’s Note: This story has been update to include quotes from WildEarth Guardians.

NEW MEXICO (KRQE) – Small fish continue to face big threats according to claims laid out in a new lawsuit filed today in New Mexico federal court. Non-profit WildEarth Guardians allege that despite following guidance by the U.S. Fish and Wildlife Service, the U.S. Bureau of Reclamation is threatening the Rio Grande Silvery Minnow.

Despite being only a few inches in length, the silvery minnow has long been the center of attention in discussions surrounding New Mexico’s environment. Since 1994, the species has been on the federal government’s list of endangered species. The species is also protected under state law.

The number of silvery minnows shrunk dramatically from the 1950s to the 1990s, in large part because of dams set up across the Rio Grande, according to the New Mexico Department of Game and Fish. After silvery minnows were added to the endangered species list, the U.S. Fish and Wildlife Service issued an opinion concluding that the U.S. Bureau of Reclamation’s continued diversion of water from the Rio Grande is not likely to significantly harm the fish.

But WildEarth Guardians disagrees. They’re arguing that the 2016 Fish and Wildlife Service opinion wasn’t done properly. For instance, they claim that the Fish and Wildlife Service opinion didn’t properly address how the cumulative effects of climate change might add to any affects from damming and river diversion.

“The lawsuit is being filed now because we’ve had nearly six years of operating under this plan [the 2016 opinion] to see if it was going to work,” Daniel Timmons, a spokesperson for WildEarth Guardians, told KRQE News 13. “WildEarth Guardians has been suspicious for years that the plan did not set forth enough concrete mechanisms to ensure that that it was going to be effective.”

With that logic, WildEarth Guardians is asking the federal court to invalidate that 2016 Fish and Wildlife Service opinion and re-study the potential impacts that U.S. Bureau of Reclamation diversion might have on the minnows. They’re also asking the court to award any relief that might protect the public interest.

KRQE News 13 reached out to both the U.S. Bureau of Reclamation as well as the U.S. Fish and Wildlife Service for comment. The Bureau of Reclamation and Fish and Wildlife Service said they can’t comment on pending lawsuits.

“We gave the agencies the benefit of the doubt to see if it was going to work,” Timmons from WildEarth Guardians says. “And the [fish] population numbers for the past couple years have just been so dire that it’s clear the writing is on the wall, that this plan is not having the impact that we thought that it might.”

Over the years, several groups have worked to save New Mexico’s silvery minnows. That work gained an increased sense of urgency earlier this year, when portions of the Rio Grande ran dry.

Timmons says that protecting the fish is more than just an environmental endeavor. “It’s a cultural heritage. And it’s irreplaceable,” Timmons says. “The silvery minnow is the last of its kind in this river system.”