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Scientists want to know if Rio Grande contaminants are feminizing the endangered silvery minnow

August 25, 2010, 1:00 am
After a soaking monsoon rainstorm, the Rio Grande through Albuquerque runs red. The next morning, as its waters again recede, spadefoot toads the size of quarters scamper atop the mud. Tiny fish wiggle into pools pressed by the river into the banks, and awkwardly-aloft ducks crash-land into the water. For a few hours, it’s easy to imagine this is a natural river, dependent only upon storm clouds and seasons for its ebbs and flows.

In fact, the Rio Grande is manipulated and managed, overused and oftentimes abused. Since the early 1990s, the conservation group American Rivers has repeatedly included the Rio Grande on its list of endangered rivers; in 2007, the group named it the world’s seventh most endangered river. Farmers and municipalities vie for water. During heavy rainstorms, urban runoff fouls its flows. Albuquerque’s wastewater treatment plant is the river’s sixth largest New Mexico tributary.

At the center of the debate over the river’s health is a 4-inch fish—the silvery minnow—whose survival is intricately linked to the water in which it lives.

In recent years, scientists have begun finding fish within the Rio Grande that are “intersex”—that is, male fish with egg cells within their testes. Now, biologists are embarking upon additional studies to learn how certain chemicals within water from wastewater treatment plants—which, during dry times, makes up a significant portion of the river’s flow—are affecting the Rio Grande’s native fish populations, including the endangered silvery minnow.

Already, the minnow can’t survive without help. Each year, biologists stock the river with hatchery-raised fish. Then, when the river dries during the summer months, salvage crews return to rescue minnows from shrinking pools of warm water.

It wasn’t always like this. Sixty years ago, the silvery minnow swam the length of the 1,850-mile-long Rio Grande and its tributary, the Pecos River. But as farming intensified and cities sprawled, water quality fluctuated and river levels dropped. Now, the fish is found only in pockets of a 173-mile stretch of the Middle Rio Grande, which, in turn, is divided by dams into three sections. To save the fish, the US Fish and Wildlife Service in 1994 listed it for protection under the Endangered Species Act, setting off a series of court battles, agency showdowns and political wranglings that proved much more is at stake than a tiny fish.

As biologists warned that the fish needed—no kidding!—water to survive, water managers, cities and irrigation districts panicked over their claims to the river’s water. Republican and Democratic lawmakers alike agreed, and everyone from former Sen. Pete Domenici, R-NM, to Gov. Bill Richardson argued that water meant for cities should not be used to protect an endangered species.

Since the late 1990s, the state’s Interstate Stream Commission, legally responsible for delivering water to Texas, has repeatedly clashed with the Fish and Wildlife Service, and disputed the federal agency’s minnow studies and flow recommendations.

Now, the commission says it’s time for the federal government to admit the species is improving and to lift certain protections for the minnow. At the end of June, the Attorney General’s Office and the commission’s director sent a letter to Fish and Wildlife, pointing out that all of the threats to the minnow’s survival are being addressed, and many have been reduced or are inapplicable.

Credits: Interstate Stream Commission

Federal officials and activists alike were surprised by the letter. For years, WildEarth Guardians Executive Director John Horning was in the thick of the silvery minnow debate. WildEarth Guardians (formerly Forest Guardians) filed suit against federal agencies for mismanagement, and also worked within a coalition to create a water reserve for the fish during dry times. In recent years, agencies and stakeholders have learned to better work together, Horning says, and there are opportunities that didn’t exist a decade ago. Perhaps more significantly, the past few summers have been relatively wet compared with those earlier in the decade.

“I still think the great threat to the health of the Rio Grande and to fish is water of sufficient quantity—well, fish need water,” Horning says. “And basically, the river gets sloppy seconds.”

As it turns out, those sloppy seconds may have serious environmental repercussions.
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