DOINews: USFWS: Hatching Fish in the Desert

This article appeared in the March/April edition of Refuge Update.

Working in a harsh environment with one of the rarest fish on Earth, the U.S. Fish and Wildlife Service, National Park Service and others are doing unprecedented conservation research at a special facility within Ash Meadows National Wildlife Refuge in Nevada.

The Fish and Wildlife Service is collecting endangered Devils Hole pupfish eggs from a warm spring that is within the desert refuge but is jurisdictionally part of California's Death Valley National Park; transporting those eggs four miles to the Ash Meadows Fish Conservation Facility; and hatching and rearing larvae in captivity. The goal is to determine if it's feasible to establish a backup population using new methods developed by University of Arizona – Tucson researcher Olin Feuerbacher, now a Service biologist.

	The Devils Hole pupfish's only natural habitat is Devils Hole, an underwater cavern that is physically within Ash Meadows National Wildlife Refuge in Nevada but is jurisdictionally part of California's Death Valley National Park. Photo by Olin Feuerbacher, USFWS.

So far, 33 larvae have hatched from collected eggs and 29 fish (88 percent) are alive and healthy.

This is being done to bolster the species' odds of survival. Last fall, only 65 Devils Hole pupfish were observed in their only natural habitat, Devils Hole — an underwater cavern whose water is nearly always 92.3 degrees Fahrenheit and whose depth exceeds 432 feet.

“The Devils Hole pupfish is an icon of the conservation movement and was listed as endangered in 1967,” says Service biologist Darrick Weissenfluh. “Devils Hole pupfish are important because they encourage us to think about our own future and the sustainability of our activities, especially groundwater use.”

Weissenfluh manages the Service-owned Ash Meadows Fish Conservation Facility, which includes a 100,000-gallon state-of-the-art tank system that emulates Devils Hole. The facility's $4.5 million design and construction in 2012 was paid for with Southern Nevada Public Land Management Act funds. Various Service programs support its operation. It exists to save the Devils Hole pupfish and conduct research that benefits imperiled aquatic species.

Devils Hole pupfish have “much to teach scientists about adaptation to adverse conditions,” the Service's Nevada Fish and Wildlife Office Web site says. “It has adapted to survive in very warm water with very low oxygen content.”

The inch-long iridescent blue fish has been isolated in Devils Hole for 10,000 to 20,000 years. Individual pupfish live about one year and spend most of their time on a shallow rock shelf near the surface. From the late 1970s through 1996, the population seemed to be stable, with an average count of 324 individuals. In 1997, a steady decline to last fall's 65 began — for reasons mostly unknown, but that likely involve subtle habitat changes researchers are studying.

To reduce the likelihood of extinction, the Ash Meadows facility is attempting to establish a refuge population of Devils Hole pupfish that is genetically similar to the wild population — two refuge populations, actually, one in aquariums this year and another in the large tank system by the end of next year.

To do that, Weissenfluh says, facility staff members, in coordination with the Park Service and Nevada Department of Wildlife, are deploying and collecting egg recovery mats in Devils Hole to collect viable (fertilized) eggs from the wild population. The mats are deployed for up to a week and then carefully transported to the facility within 45 minutes of collection. At the facility, staff members place the eggs/mats in incubation aquariums for 10 days. Eggs typically hatch in a week.

“When they hatch, intensive husbandry efforts begin, as the larval fish can be finicky and a challenge to rear,” Weissenfluh says. “This project is just beginning, but our success to date is supporting the idea there are creative ways to conserve a species on the brink of extinction, such as collecting and propagating eggs as opposed to removing some or all of the adults from the wild.”

By: Bill O'Brian, writer/editor, USFWS

March 12, 2014