The federal proposal to reclassify the humpback chub from endangered to the less severe “threatened” status is a rare conservation win for native fish in Arizona, the state’s native aquatics program manager said.
“Not many species of native fish have been downlisted due to recovery efforts in Arizona, so it’s a really big success under the Endangered Species Act,” said Julie Carter, who works under the Arizona Game and Fish Department.
A downlisting of the chub wouldn’t change any of the current efforts to conserve and promote the fish, state and federal officials said. But it would allow state agencies more flexibility and reduces regulations associated with managing the chub, Carter said.
The Grand Canyon population of chub is doing “remarkably well,” said Scott Rogers, an aquatic wildlife program manager with the Arizona Game and Fish Department. The population began to grow in 2007 and has since stabilized at about 12,000 adult fish.
On top of that, managers have logged a more recent increase in chub abundance far downstream of the current population epicenter around the Little Colorado River, said the U.S. Fish and Wildlife Service’s Kirk Young.
Surveyors used to catch one, two or three fish below Diamond Creek, which runs through the Hualapai Reservation, Young said. Now they are catching hundreds of fish in that area, he said.
Establishing a second, distinct chub population in the Grand Canyon would be an important milestone for the species' recovery because it would serve as a backup in case something ever happened to the fish living upstream, Young said.
He said several factors could be helping boost the species' populations in the Grand Canyon, including warmer water temperatures in the mainstem Colorado River and regular efforts to transport young fish to better habitat in the Little Colorado River.
At the same time, warmer water coming from Lake Powell could help nonnative invasive fish gain a foothold in canyon, which could be disastrous for the chub, Young said.
Experiments with high flow releases from Glen Canyon Dam, meant to flush sediment into the Colorado River, haven’t had a noticeable effect one way or another on the humpback chub, several experts said.
Carter said there are likely thousands of people — from agencies to tribes to graduate students — who have worked on chub conservation over the years.
The U.S. Fish and Wildlife Service’s downlisting proposal demonstrates progress for those collaborative efforts, said Tom Chart, director of the agency’s Upper Colorado River Endangered Fish Recovery Program.
“It really doesn't lessen the concern Fish and Wildlife has with this species in my mind,” Chart said. “It just might convey to our stakeholders that we are on the right track here.”