TUCSON, Ariz.— The Center for Biological Diversity filed a formal petition today urging the federal government to expand the critical habitat designation for the Sonora chub, a small desert fish facing major threats.

Critical habitat was designated for the Sonora chub in 1986 to include the entire U.S. range of the species as it was known at the time. But a second population has since been discovered outside of the current designation, in a nearby stream known as California Gulch, in southeast Arizona. Today’s petition calls for designating approximately 4 miles of this waterway as critical habitat, starting at the international border.

“For the Sonora chub to have a shot at avoiding extinction, we have to safeguard all the U.S. habitat that’s critical to this fish’s survival and recovery,” said Krista Kemppinen, Ph.D., a senior scientist at the Center. “Only one of two wild populations is protected right now, so federal action is urgently needed. Preserving Arizona’s California Gulch is crucial to saving these little fish.”

California Gulch has habitat features such as perennial pools that are essential to the conservation of the Sonora chub. The gulch also acts a migration corridor between Mexico and the United States.

One of the major threats to Sonora chub in California Gulch is grazing by livestock, which can trample the fish and pollute and degrade their habitat. Cattle damage has already been documented in the chub’s habitat. Another major threat is border infrastructure development, with numerous small gaps in the border wall such as the one that California Gulch flows through slated to be closed.

In addition to grazing and border infrastructure development, mining, climate change, water development and non-native species also threaten Sonora chub and its habitat.

The U.S. Fish and Wildlife Service must respond to today’s petition within 90 days. If the agency determines the proposed revision may be warranted, it must state how it intends to proceed with the requested revision within one year.