Tooele Army Depot pond is a refuge for little fish fighting extinction

A small pond at the Tooele Army Depot has become a safe haven for a rare species of minnow battling threats of extinction from groundwater pumping.

The least chub is a small, colorful, minnow-like fish that, according to the Utah Division of Wildlife, thrive in spring-fed wetlands, eating algae, small insects and mosquito larvae. They used to be abundant in the Bonneville Basin of Utah, according to the Center for Biological Diversity.

But their habitats have been impacted by a number of factors, including agricultural development, water diversion and urban expansion, leaving just seven known wild populations.

In a 2021 petition to list the species as "endangered," the Center for Biological Diversity reports that spring-fed pools where many sensitive fish populations live are drying up as aquifers are pumped for agricultural irrigation and urban growth. Several fish species in the West have already been driven extinct by groundwater pumping, the report says.

The U.S. Fish and Wildlife Service proposed to list the fish as an endangered species in 1995, but retracted that proposal in 1999. A petition was filed by environmental groups in 2007 to protect the species, but the service did not act on it until it was sued, finally putting the least chub on the candidate list "to await Endangered Species Act status indefinitely," according to the Center for Biological Diversity.

The Snake Valley, near the Utah-Nevada border, is home to half of the entire least chub population, but groundwater pumping for the metro Las Vegas population may threaten the least chub's survival, and other species depending on spring-fed pools.

To combat the declining populations, the Utah Division of Wildlife began looking for partners to establish broodstock and refugee populations of least chubs.

Officials mentioned this during a visit to the Tooele Army Depot in 2010, and the environmental management department formed a plan to transform two "dry unused depressions in the ground" that had been used to water livestock 100 years earlier, into a sanctuary for the little fish, according to a project update.

Army Depot personnel went to work, removing tumbleweeds and old silt, bringing in new clay and laying pipeline left over from a previous irrigation repair job. They transplanted native plants from the banks of Ophir Creek and the Rainbow Reservoir on the installation. They filled the ponds and allowed overflowing water to create a wet meadow in an adjacent field for more birds and wildlife.

In October 2011, 500 least chubs were transferred from a Division of Wildlife hatchery in southern Utah to the Tooele Army Depot.

Keith Lawrence, native aquatics project leader for the division, said in a statement they "don't have to worry about a potentially detrimental species being introduced there. (The Tooele Army Depot) satisfies the two critical characteristics that are difficult to find at other refuges, even in nature: water security and bio security from fish and avian predators. It's these types of vital partnerships that have helped prevent the listing of the species."

In the latest update sent out Wednesday, Lawrence said they have "a stable population, and the habitat is very good."

Scientists do not try to count the number of least chubs, but say the population “surely numbers in the thousands and might exceed 5,000.”