Biologists’ research leads to withdrawal of two fish from ‘endangered’ classification

The headwater chub, roundtail chub and Gila chub have been reclassified as one species, the roundtail chub, which AZGFD biologists say should not be listed under the endangered Species Act.


The headwater chub, roundtail chub and Gila chub have been reclassified as one species, the roundtail chub, which AZGFD biologists say should not be listed under the endangered Species Act.

PHOENIX — The U.S. Fish and Wildlife Service (USFWS) withdrew its proposal to list two minnows, the headwater chub and a distinct population segment of the roundtail chub in the Lower Colorado River Basin, as threatened species under the Endangered Species Act (ESA) April 6.

The Service’s decision came as a result of new scientific classification information that in 2016 led the American Fisheries Society and the American Society of Ichthyologists and Herpetologists Joint Committee on the Names of Fishes – the recognized authority on fish taxonomy — to consider the headwater chub and roundtail chub (and the Gila chub, which is currently listed as endangered), to be a single species: the roundtail chub.

Arizona Game and Fish Department (AZGFD) biologists in 2015 conducted a complete review of all data and scientific literature available to determine if the available science supported the recognized taxonomic designations of the three species of chub. The department’s review found no justification to support the separation of chub into three separate species, and concluded they should be classified as a single species.

Subsequently, AZGFD requested that the American Fisheries Society re-evaluate the recognized taxonomic designation of the three species.

The analysis was assigned to the Joint Committee, which conducted months of review and listened to presentations by fisheries scientists on the morphology and genetic status of chub. In September 2016, the Joint Committee concluded there is no morphological or genetic data that define populations of roundtail chub in the lower Colorado River basin as members of more than one species.

“The Joint Committee’s determination last year, along with today’s U.S. Fish and Wildlife Service decision, is a huge win for chub and for those who manage and conserve chub in the lower Colorado River basin,” said Chris Cantrell, aquatic wildlife chief for AZGFD. “The taxonomic history of this species has been debated for decades, which has influenced our management strategies and our ability to implement conservation on a range-wide basis. The decision will open doors to more opportunities to protect and conserve chub in Arizona.”

“I am pleased to see the USFWS is paying attention to Arizonans and deciding against adding to an already lengthy list of threatened and endangered species in Arizona,” said Sen. Jeff Flake.

Steve Spangle, Arizona Field Supervisor for USFWS, said in a news release that ESA determinations are founded on the best available science.

“When new science becomes available, especially midstream in a listing process, we evaluate it and respond accordingly,” he said. “Our withdrawal of the listing proposal for the former headwater chub and roundtail chub reflects this new science indicating that these are no longer valid species.”

USFWS, together with conservation partners, intends to conduct a species status assessment of the now-larger roundtail chub taxon. This includes the Gila chub, which has been protected under the ESA since 2005. The taxonomic revision of the chubs resulted in Gila chub being recognized as a part of the larger roundtail chub species, necessitating a re-evaluation of its ESA status. Pending this evaluation, the Gila chub will remain protected under the ESA. The Department encourages the Service to make swift resolution to remove the ESA status of Gila chub based on the findings of the Joint Committee and the best available science.


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