Dead Fish at Nevada Refuge Linked to Salinity

Biologists have tentatively blamed the deaths of an estimated 7 million fish at the Stillwater Wildlife Management Area in northern Nevada on high salt levels in the nature refuge’s waters, a Nevada Wildlife Department spokesman said Thursday.

“I don’t think that there’s any doubt that they’re (the fish) dying because of salinity levels,” said spokesman David Rice, who added that unless the situation is reversed, the wildlife refuge faces “doom.”

Meanwhile, state wildlife officials have also concluded that the estimated 1,500 migratory birds that have died in the area over the past few weeks were killed by a coincidental outbreak of avian cholera.

The fish--8- to 10-inch scavengers called tui chub--were killed because of extremely salty water in the Carson Sink, a vast basin that is the natural terminus of the Carson and Humboldt rivers.

Rice and scientist Terry Young of the San Francisco-based Environmental Defense Fund said Thursday in telephone interviews that unless fresh water can be diverted into the Carson Sink, located about 60 miles east of Reno, the entire Stillwater National Wildlife Management Area will be threatened. The management area includes both the Carson Sink as well as two wildlife refuges.

“The catastrophe at Stillwater refuge (results from) the fact that we do not have sufficient flows of fresh water on a regular basis, and that in itself could someday spell doom for Stillwater,” Rice said.

Much of the Carson River water that historically flowed into the sink has been diverted for agricultural and municipal use. Drain water from the alfalfa, winter wheat, barley and melon fields then percolates through the soil, picking up natural salts, before flowing to the Carson Sink. The salts then become extremely concentrated in the sink.

“This refuge and many others in the West have no clean water supply,” Young added. “They take the used and often very polluted water that is left over from agriculture and municipal users and sooner or later that is going to have an effect.

“We’ve seen that happen at Kesterson National Wildlife Refuge (in Los Banos, Calif.) in 1983 and 1984, and at the neighboring Grasslands Water District in 1985, and now in 1986 and 1987 at the Carson Sink,” she said.

Rice said the state concluded that the fish were killed by highly saline water after the Nevada Department of Wildlife detected concentrations of dissolved salts at levels as high as 33,000 parts per million. Comparison figures for drinking water were zero to 300 ppm. At 33,000 ppm., the water is two-thirds as salty as the ocean, Rice said.

U.S. Fish and Wildlife Service officials were in an all-day meeting with Nevada officials and could not be reached for comment. Federal authorities have not completed their examination of the dead fish, or completed a more detailed analysis of the water. Examinations of other dead birds are pending. However, Rice said, federal officials have informally agreed with the conclusions of Nevada officials.

The situation in the Carson Sink has been developing for several years. The Carson and Humboldt rivers reached flood stage three years ago and dumped vast amounts of water into the sink. Since then, the water has been gradually evaporating, leaving the remainder increasingly salty. In the past two years, the salty water has claimed both trout and carp. Beginning shortly before Christmas, the tui chub, which are the most salt-tolerant of the fish in the refuge, started dying.

On Thursday, officials revised their estimate of the number of fish killed, from 3 million to 7 million. They said that amounted to 72 dead fish for every foot of the Carson Sink’s 30-mile shoreline.

About two weeks ago, a variety of migratory birds also began dying, including three kinds of ducks, cormorants, geese, egrets, blue herons, coots, ravens, white pelicans and California gulls.

Simultaneous Deaths

The simultaneous deaths of fish and fowl alarmed wildlife biologists and environmentalists. One described the situation as an “eco-catastrophe.”

But Thursday’s announcement seemed to indicate that the bird deaths were not directly related to the deaths of the fish. Stephen Bailey of the California Academy of Science’s ornithology and mammalogy department in San Francisco, said Thursday that major outbreaks of avian cholera with high death rates have been known to occur in waterfowl on migration or at their wintering grounds.

He added that stress factors such as severe weather, food shortages, other diseases or toxic chemicals can make birds more susceptible to avian cholera and other diseases.