The agency also designated another 200 miles of critical river and stream habitat for the spikedace and loach minnow in response to a lawsuit filed by environmentalists.
In all, more than 700 river miles are now considered critical for the fishes’ survival. The list includes portions of the Gila and San Francisco rivers, the Blue River and its tributaries and a handful of creeks.
“We’re glad there’s a recognition that these guys are really in trouble,” said Noah Greenwald, endangered species director at the Center for Biological Diversity, which challenged the agency over a 2005 decision to limit critical habitat to fewer river miles.
Biologists estimate the range of the two fishes has been reduced by more than 80 percent.
At less than three inches long, the fish are found in moderate to swift-flowing rivers and streams. Their populations in central and eastern Arizona and western New Mexico have become smaller and more fragmented over the years.
With an endangered classification, the fish are now considered on the brink of extinction. Federal rules for managing such species and protections under the Endangered Species Act are more rigid than those for threatened species.
The Fish and Wildlife Service will not have as much flexibility when dealing with the two species. Recovery of the fish will depend greatly on partners in both states, the agency said.
Greenwald acknowledged that persistent drought and increased water withdrawals throughout the region will continue to be challenges for those working on saving the fish.
“The Southwest is definitely going to have to get better at using water than it already is if there’s going to be any hope, not just for these fish, but virtually every native fish,” Greenwald said. “The population of almost every species that depends on rivers and streams in the Southwest has gone down.”
The Fish and Wildlife Service prepared an economic analysis before making its decision to designate more critical habitat. It found the designation could result in impacts ranging from $2.3 million to $6.7 million over 20 years for activities such as water use, grazing, recreation, development and fire management.
The agency excluded some areas from the critical habitat designation, including streams on tribal lands in Arizona and those on lands owed by the copper producer Freeport McMoRan in Arizona and New Mexico due to existing commitments to recovery of the fish.