Friday, April 10, 2009
Feds Propose Change in Silvery Minnow Plan
By Susan Montoya Bryan
How many endangered Rio Grande silvery minnows does it take to ensure the species doesn't disappear from the wild?
There's no magic number, but the U.S. Fish and Wildlife Service announced Thursday that biologists with the minnow recovery team have come up with a scientific model to determine when minnow populations are self-sustaining and when the agency can consider downlisting the small fish.
The number of minnows in the Rio Grande in New Mexico and Texas at any given time is less important than how the fish does over many years since it has such a short life span and radical changes in its reproductive rate, said Jennifer Norris, the Fish and Wildlife Service's coordinator for endangered species on the Rio Grande.
"The model will look at birth and death rates over time and give you a trajectory of where it's headed into the future. Then you can measure that against the probability that it will go extinct within 50 years or 25 years, that sort of thing," she said.
The agency is proposing that the so-called population viability analysis be included in a draft of the minnow recovery plan that's currently under review. The public has until May 26 to comment on the proposal.
A final recovery plan is scheduled for completion later this year.
The minnow, which was listed as endangered in 1994, used to be abundant in the Rio Grande and some of its tributaries from northern New Mexico down to the Gulf of Mexico.
Due to pressures on the river and changes in habitat, the minnow today only occupies a fraction of its historic range <0x2014> stretches of the Rio Grande in central New Mexico and Texas' Big Bend.
In the Middle Rio Grande Valley, limited water supplies have often pitted minnows, farmers and other water users against one other. A federal mandate requires some water in the river for minnow.
John Horning, executive director of the environmental group WildEarth Guardians, said Thursday that science is essential in guiding species recovery but what the Rio Grande <0x2014> and the species that depend on it <0x2014> needs more than anything is "a right to its own water."
"The magic number is a whole and healthy river, which is first and foremost measured by securing and providing adequate flow," Horning said. "The Fish and Wildlife Service and the state of New Mexico and the rest of the water users have failed and continue to fail on that lone critical barometer."
He said he would prefer the agency focus on flows and the river's entire ecosystem rather than its population model for the minnow.
The agency spent about a year developing the model, and Norris said it will provide better criteria for recovery than what's in the current plan. She said biologists will be able to get a better handle on when extinction risk has been reduced to a point where they are confident the fish will persist.
The minnow did well last year because the river did not dry up, but Norris said forecasts for a dry summer this year could have fatal implications for the fish.
"It's a year-to-year thing in the middle valley and a lot of it depends on how we're doing with habitat restoration and improving the genetic viability of the species," she said. "We're taking baby steps. We're moving in the right direction but we're not ready to call (the population) self-sustaining."
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