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

August 25, 2010, 1:00 am

The Las Lunas refugium is one of several sites where biologists raise silvery minnows in captivity for introduction into the wild.
Credits: Interstate Stream Commission

For the Fish and Wildlife Service, the mandate is to enforce the federal Endangered Species Act by recommending river flows for fish habitat and working to boost populations. But the New Mexico Interstate Stream Commission has its own obligations—to the citizens of New Mexico.

Its role is to protect, serve, investigate and develop the waters of the state—both interstate and intrastate streams—and to comply with interstate compacts, or agreements, that deliver water to downstream states. According to its director, Estevan López, the commission also must ensure that New Mexico receives the full benefit of those agreements.

In the case of the minnow, he says, when Fish and Wildlife established minimum flow requirements, it could have affected the commission’s ability to meet compact obligations with Texas.

“We really got involved in a serious way about trying to make sure that whatever requirements are established for maintaining the fish are things we think are doable,” he says. “Secondarily, one of our statutory charges is to protect the waters of the state, and so we look at it from the perspective of protecting existing and planned future uses [of water] by the citizens of the state.” He points out that, in the past decade, the commission has spent approximately $10 million on work related to the silvery minnow.

By requesting that Fish and Wildlife downlist the minnow from endangered to threatened, as it did in June, López says the commission is acknowledging the work biologists, agencies and stakeholders have accomplished through the Middle Rio Grande Endangered Species Collaborative Program.

“It probably wouldn’t change anything immediately for us,” he says. “I think more than anything it would be recognition that we’re on the right path.”

He adds that the commission submitted its request to Fish and Wildlife as part of a status review of the fish—not because it plans to pursue litigation or step back from its role within the collaborative program.

That said, López thinks water managers should have more flexibility—to learn from how the fish is responding to recovery work by biologists—and to adapt to conditions, rather than having to follow Fish and Wildlife’s requirements at all costs.

The commission also hires its own biologists—from private consulting firms—to carry out fish studies.

“I don’t know if I would want to characterize it as contradicting the studies of the Fish and Wildlife Service but, rather, I think we’ve refined the questions that we’re asking, and we’re doing a better job of really understanding the answers to those questions as we shape them better,” López says.

From his perspective, for instance, the issue of river flows is not clear-cut.

“Clearly, if we had the luxury of having water in the entire length of the river every year, that would be great, but I think that, even under pre-development conditions, there were years when you had drying,” he says. “I think we have to recognize that’s the sort of environment the fish evolved in and take other actions that will allow it to rebound when there is drying.”

He points out that the minnow’s increased numbers within the past few years show there is probably more management flexibility than people had considered in the past. As a result of the collaborative program, the fish is doing much better than it was a decade ago, he says. But perhaps it’s time for a change in mind-set.

It’s difficult for most people to care a whole lot about almost any species of fish—never mind a 4-inch-long minnow. Even Remshardt acknowledges that.

“It’s not the minnow itself, but what the minnow represents: the river,” he says.

The minnow began as a native species on the brink of extinction. It’s become a key reason there’s water in the river.

Interstate Stream Commission Director Estevan López says his agency has to ensure it meets the state’s water obligations to other states and New Mexico’s citizens.

It doesn’t take much to notice the difference between stretches where the minnow is protected—where there are cottonwoods, birds and other wildlife—and, say, the river as it flows through El Paso, Texas.

“There, the Rio Grande is a trapezoid concrete ditch—where there is no biological protection—and that’s sort of what you end up with, where they channelized it and tried to move it away from the city as quickly as possible,” he says. “It’s just a conveyance channel for more irrigation water.”

The minnow has its own benefits to the ecosystem, he says, and its own reason to exist.

Like the state, Fish and Wildlife also hopes to someday remove the fish from protection under the Endangered Species Act.

“Everybody wants to see the fish delisted,” he says. “It’s just that we want to see it delisted because it’s surviving.”  SFR
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