Given a second chance

Warm Springs pupfish gets its name from its playful nature during mating season. Despite its hardiness, the fish remains on the list of federally threatened or endangered species due to predation by invasive species. Credit: USFWS

Warm Springs pupfish get another opportunity for survival in the desert

By Pacific Southwest Region External Affairs
June 27, 2018

In a multi-year effort, U.S. Fish and Wildlife Service biologists and volunteers recently eradicated the red swamp crayfish, an invasive species threatening the endangered Warm Springs pupfish found at the Ash Meadows National Wildlife Refuge.

Ash Meadows springs system is an island of water in the middle of the Nevada desert. It has one of the highest levels of endemic species on the continent. Credit: USFWS

Ash Meadows, Nevada is a system of about 50 springs, made up of ancient waters.

This desert oasis is unique in its high rate of endemism, providing suitable habitat to a number of species found only in and around the refuge.

“It’s essentially an island in the middle of the desert,” says Corey Lee, refuge manager. “It’s just an island of water instead of an island of land.”

Warm Springs pupfish

Pupfish get their name from the way they playfully chase each other during mating season. The small fish mate many times throughout their short six-to-nine month lifespan.

Warm Springs pupfish can tolerate varied environmental conditions, including shifting pH and salt levels and changes in water temperature. Due to the fluctuating conditions of the springs on Ash Meadows, the pupfish can thrive where other species may not.

Michael Schwemm, senior fish biologist for U.S. Fish Wildlife Service, and Hal Fairfield, a volunteer with the U.S. Fish Wildlife Service, examine a spring in search of Warm Springs pupfish. Credit: USFWS

“What's really unique about pupfish, in particular the Warm Springs pupfish, is not that it has one particular trait that locks into a particular habitat type, but that it exhibits this really wide tolerance of biological conditions,” says Michael Schwemm, senior fish biologist with the Service’s Southern Nevada Fish and Wildlife Office. “And that’s what makes the pupfish successful and able to survive in a really harsh environment such as the Mojave Desert.”

Red swamp crayfish is one of the major invasive species that threatened the livelihood of the Warm Springs pupfish. Credit: USFWS

Despite its hardiness, the fish remains on the list of federally threatened or endangered species due to predation by invasive species.

Non-Native Species

Non-native species including red-rimmed melania snail, western mosquitofish and red swamp crayfish are the most troublesome for the pupfish because they prey on the fish in every stage of their life cycle. The crayfish can also disturb the spring habitat to such a degree that it becomes difficult or even impossible for the native fish to spawn.

A native of the gulf coast, red swamp crayfish are extraordinarily adaptive and have adjusted to the desert environment. They can burrow underground when the water dries up, and emerge when it returns. They can also travel over land from spring to spring, making it more difficult to eradicate.

The Solution

To protect the pupfish, Service biologists are working one spring at a time to eradicate the invasive crayfish population. To do this they safely remove the pupfish, as well as the invertebrates and various algae on which they feed, and move them to aquariums for temporary safe keeping.

The crayfish are then removed from the spring, after which water is diverted from the ponds until the area is completely dry. This ensures that any crayfish that have burrowed underground are not alive when the water is diverted back to the spring.

A Warm Springs Pupfish at the mouth of a fish trap in a spring at Ash Meadows National Wildlife Refuge. Pupfish were captured and moved to aquariums, then released once the restoration work was completed. Credit: USFWS

“In the summertime, it regularly gets over 115 degrees, so water has a tendency to dry out really fast,” says Lee, “[But] some of these projects did take a little longer than they expected. He continues, “It took almost two years for individual springs to actually dry out… and completely rid them of crayfish.”

When the area is deemed cleared of crayfish, the spring water is reintroduced to the pond. If there are still no signs of crayfish after the water returns, the pupfish are brought back, and crayfish cages are set up to prevent a new invasion.

In the springs cleared to date, there are no signs of the red swamp crayfish, and the native pupfish are thriving.

“To our knowledge,” says Schwemm, “no other refuge has been able to successfully remove red swamp crayfish from an area.

“There’s a number of things that inspire me to work at systems such as Ash Meadows. For me, there’s a unique and unassuming biodiversity that exists in such a harsh landscape… I don’t want to give up on species that have managed to live here this long. I feel we have an obligation to preserve and protect them.”

A resilient species, Warm Springs pupfish can endure a variety of biological conditions but faces threats from the invasive red swamp crayfish. Endemic to Ash Meadows National Wildlife Refuge, Warm Springs pupfish has a short lifespan of six to nine months. Credit: USFWS

VIDEO: In a multi-year effort, U.S. Fish and Wildlife Service biologists and volunteers recently eradicated the red swamp crayfish, an invasive species threatening the endangered Warm Springs pupfish found at the Ash Meadows National Wildlife Refuge. Credit: USFWS