An icon of the Rio Grande has all but vanished in the wild

Despite five years of drought, and at least 25 miles of dry riverbed on the Rio Grande so far this summer, some say the endangered silvery minnow is getting along just swimmingly.

"The minnow is such a lucky species," says Joy Nicholopolous, state supervisor of the U.S. Fish and Wildlife Service’s Ecological Services Office in Albuquerque. "I shudder to think where it would be if it weren’t for the collaborative effort."

Over the last decade, this pipsqueak of a fish has brought together — sometimes in court, but more often in a meeting room — federal, state and tribal biologists, state water managers and local irrigators. Since 1994, when the Fish and Wildlife Service first protected the minnow under the Endangered Species Act, biologists, lawyers, judges, bureaucrats and environmentalists have agonized through hundreds of hours of negotiations. They’ve discussed recovery plans, fought over water allocations and hashed out everything from fish genetics to the type of donuts served at morning meetings.

Last year, Congress solidified into law a 2003 agreement between the Wildlife Service and the Bureau of Reclamation, designed to prevent the minnow’s extinction while at the same time ensuring water for farmers and cities (HCN, 2/16/04: Congress overrules the courts). Biologists have also started collecting eggs to be bred at the Service’s hatchery in Dexter and the City of Albuquerque’s new $1.7 million "refugium."

But while Fish and Wildlife Service higher-ups trumpet their success, biologists tell a different story: "The density (of minnows) has declined dramatically," says John Pittenger with Blue Earth Ecological Consultants, a member of the silvery minnow Recovery Team. "The fish is in imminent danger of extinction in the wild."

"Rock-bottom" fish

Fifty years ago, the silvery minnow swam the length of the 1,850-mile-long Rio Grande and its major tributary, the Pecos River. But as farms and cities spread along the rivers, the water quality fluctuated, and river levels dropped. Now, the fish is found only in pockets of a single 173-mile stretch of the Middle Rio Grande in central New Mexico. And its population is now declining dramatically: In 1995, more than half the fish in the Middle Rio Grande were silvery minnows. Now, the minnow accounts for less than a half of a percent of the fish there.

The fish has a life history similar to that of a cottonwood tree, which drops millions of seeds, only a few of which survive. Likewise, a minnow population produces millions of eggs: "You need those numbers for the long-term sustainability of the species," says Pittenger.

In 2002, when biologists first began collecting eggs for the captive breeding program, they brought home more than a million eggs. The following year, they found 400,000; this spring, they found only 126. "That’s practically zero," says Manuel Ulibarri, director for the Dexter National Fish Hatchery and Technology Center. "Either the adult population isn’t out there, or it didn’t spawn."

To survive in the wild, a population must also have a certain degree of genetic variation. According to a recent University of New Mexico study for the Bureau of Reclamation, the wild population of silvery minnows needs more than 4 million "potentially breeding adults" to survive.

Despite the efforts of biologists to stock the river with hatchery fish, the minnow’s numbers continue to decline. This year, university biologists found 418 fish, and federal biologists found another 1,400. The data are still preliminary, but the numbers are significantly lower than in 2003, when university biologists reported to the Middle Rio Grande Endangered Species Collaborative Program that the number of silvery minnows found in 2003 had "declined to the lowest levels ever recorded."

"If we weren’t stocking, it would be even worse," says Jason Remshardt, with the Fish and Wildlife Service’s New Mexico Fisheries Resource Office. But he worries about the loss of genetic diversity in the wild: "We don’t want to swamp the existing (wild) population with fish who may have lost some of their fitness for living in the wild."

But to hear it from the biologists, the situation is dire. "The fish is at rock bottom," says Jim Brooks, project leader at the Service’s Fisheries Resource Office. "We are completely replacing wild fish with stocked fish."

Eggs in two baskets

The silvery minnow hasn’t vanished entirely; the two captive breeding programs each produce between 200,000 and 300,000 fish annually. But that’s still less than a tenth of the number needed to maintain acceptable genetic variation. And pulling a wild species back from the brink of extinction is different from raising fish in tanks.

"You can breed them, but they still need someplace to go," says Chuck Hayes, assistant chief with the conservation services division for nongame and endangered species for the state Department of Game and Fish. "The refugium is not the silver bullet in itself."

Federal, state and tribal biologists all point to the problem of river fragmentation. Today, the river has been reduced to mini-rivers, where minnows are cordoned into four separate stretches. When the river dries up, they are trapped in smaller stretches, and even in puddles. "Habitat fragmentation is always a bad thing," says Alex Puglisi, the biologist who heads the Environment Department for the Pueblo of Sandia. "The life history of the fish is so complex; if you take away access to the river at any one of (its) life stages, you have a problem."

Although the fish population is declining in those reaches south of Albuquerque that dry up in the summer, Nicholopolous says biologists are finding "young of year," or hatched eggs that were stocked earlier this year in upper reaches: "That’s really encouraging, and far outweighs any decline we’ve seen in the lower reaches."

But river management is beyond the scope of the recovery team and the collaborative project, unless the Fish and Wildlife Service backtracks and renegotiates with the Bureau of Reclamation. Asked if the agency plans to do that, Nicholopoulous replies, "Absolutely not" — although the Endangered Species Act requires the agency to consult with the BuRec whenever there is a "significant" decline in the species’ population.

"We haven’t been stabilizing the fish the last two years," says Brooks. "We’ve just been trying to keep them from going extinct."

The author is HCN assistant editor.

This story was funded by the McCune Charitable Foundation.

Population Study of the Silvery Minnow by the University of New Mexico www.hcn.org/downloads/rg_popmon03final_20040415.pdf

The Fish and Wildlife Service provides information on the critical habitat rule, the 2003 biological opinion, its appendices and related EIS information

• Wildlife