Climate study yields bad news for tiny desert fish

Reno, Nev. • For 10,000 years, a tiny iridescent blue fish has lived in the depths of a cavern in Nevada's desert. But a new study says climate change and warming waters — and its lack of mobility — are threatening its existence and decreasing its numbers.

Scientists studying climate change anticipate that as Earth continues to warm, fish and wildlife will migrate away from the equator or seek higher ground for a cooler habitat.

"The catch phrase is 'Migrate, Adapt or Die,'" said Mark Hausner, a hydrologist at the Desert Research Institute in Las Vegas.

But what about creatures like the endangered pupfish that exist in only one place and simply cannot pack up their bags and move?

Hausner examines that dilemma and its ramifications as the lead author of a new study — "Life in a Fishbowl: Prospects for the endangered Devils Hole pupfish in a changing climate."

The inch-long fish lives in a 426-foot-deep, water-filled cavern in the Mojave Desert on the edge of Death Valley National Park. In the 1970s, there were more than 500 pupfish, but today, there are only 92, according to the National Park Service.

The slowly rising temperature of the geothermal water — as high as 97 degrees at times — is near the limit of what the pupfish can withstand on the shallow shelf where it breeds just below the surface.

Warming water has decreased by 10 percent the 2 1/2-month period when temperatures are conducive to egg hatching and there's enough food to sustain larvae, according to the study published in the American Geophysical Union's journal, Water Resources Research.

The fish with a lifespan of 10 to 14 months has seen its 10-week hatching period shortened by a week during the past two decades, and it likely will shrink another two weeks by 2050, the study concludes.

"This is a fish that does live in a fishbowl, an incredibly hostile fishbowl," said Scott Tyler, a geological science professor at the University of Nevada, Reno, who co-authored the study.

"The water itself is warmer than the air temperature, so the air cools the water. But now that we are heating up the air, it is cooling the water less," Tyler told The Associated Press. "There's no question that the temperature is going to rise and no question that the fish is going to be affected."

Lower water levels resulting from industrial pumping in the 1960s, lack of food and inbreeding also are blamed for the fish's demise. But the study warns additional stress from climate change poses the greatest threat to date for a species that has "most likely gone through tremendous genetic bottlenecks in its more than 10,000 years of evolution."

"There is nowhere to migrate because there's no connection to any other body of water. So they are left with, 'adapt or die,'" Hausner said.

The scientists used fiber-optic cable with temperature-sensing equipment to monitor temperature changes in the cavern's water. The research team, which included the National Park Service and the U.S. Geological Society, combined climate projections, water-circulation models and ecological studies to project the impact climate change could have on the pupfish.

The pupfish was declared endangered in 1967. In 1972, the pupfish population was estimated at 553, but dropped to 171 a decade ago. Last year, the count was as low as 35, the study said.

Since then, scientists have hatched and reared 30 new fish in a specially designed facility.

Kevin Wilson, aquatic ecologist at the park's field office in Pahrump, said the transplanting effort has at least slowed the population decline and has raised hopes that the fish will recover.