NEWS RELEASE
April 2, 2025
Arizona Game and Fish Department (AZGFD) biologists successfully stocked more than 450 desert pupfish into Ayer Lake on March 26, marking an important return for these endangered fish to Boyce Thompson Arboretum.
“The Boyce Thompson Arboretum is excited to partner with Arizona Game and Fish on conserving the endangered desert pupfish,” said Kim Gray, executive director of Boyce Thompson Arboretum. “This species is an important part of the ecosystem and our lake provides the perfect habitat for them.”
Ayer Lake, which has been an important refuge site for endangered native fish for decades, needed to be drained over a year ago for essential dam repairs.
“The fish were removed, and we placed them in a pool and fish tank in our greenhouse for safekeeping,” said Gray. “They have been very happy and have even produced offspring.”
Pupfish collected from two other refuge sites—Cottonwood Tank at Robbins Butte Wildlife Area and the Phoenix Zoo Aviary pond—joined the Boyce Thompson fish in their new lake home.
“I’m really excited to get these endangered desert pupfish back into Ayer Lake,” said Brett Montgomery, AZGFD topminnow and pupfish specialist. “It’s such a nice habitat where the fish will really have the chance to thrive.”
Superior Mayor Mila Besich lent a hand getting the pupfish back into the lake by grabbing a net and helping stock some of these tiny desert fish.
“The release of the pupfish into Ayer Lake was an experience I will not forget,” said Mayor Besich. “We are proud of the important role that the Arboretum plays in sustainability and appreciate the role of Arizona Game and Fish in protecting and preserving habitats for our wildlife.”
Ayer Lake provides important habitat for these endangered desert dwellers, and in return, the pupfish bring some benefits of their own to the arboretum.
“Desert pupfish eat aquatic invertebrate larvae, so they can help keep the mosquito population down and they also help control aquatic vegetation,” said Montgomery. “Plus they’re just really cool fish that are beautiful to look at and fun to watch.”
To have this endangered species at Boyce Thompson, the arboretum entered into a Safe Harbor Agreement (SHA) with AZGFD and the U.S. Fish and Wildlife Service. The SHA outlines responsibilities for protecting the pupfish, such as creating replicate populations, minimizing the stocking of mosquitofish and other nonindigenous species, and educating the public about the threats faced by Arizona’s endangered native fish populations.
It’s also critical that the public never release unwanted aquatic pets or attempt to move fish into this or any other body of water.
“Introducing a non-native species to this lake could mean we have to start this entire process over,” said Montgomery, “instead of moving on to the next phase of endangered fish recovery here at Boyce Thompson.”
AZGFD plans to add endangered Gila topminnow to Ayer Lake as well, once the pupfish have had time to adjust.
“The arboretum has abundant wildlife and we actively curate our garden spaces to accommodate the various species that make their home here,” said Gray. “We’re excited to expand our partnership with AZGFD in the future.”
Desert pupfish are small (usually less than three inches in length) and are silvery gray with the females displaying dark markings on their sides. During breeding season, males turn bright blue with yellow tails and aggressively defend their territory. Desert pupfish are evolutionarily suited to harsh climates, able to tolerate both extremely hot and cold temperatures, as well as low oxygen, high-salinity water.
