Gila trout

Gila trout
U.S. Fish and Wildlife Service · Public domain · source
Name	Gila trout
Status	Endangered
Status system	ESA
Genus	Oncorhynchus
Species	apache
Authority	(R. R. Miller & Hubbs, 1963)

Gila trout is a species of freshwater salmonid native to the Southwest United States known for its restricted range and conservation significance. It has been the focus of interagency recovery planning involving federal, state, tribal, and nonprofit organizations and has appeared in legal and ecological literature related to endangered species, habitat restoration, and watershed management. Recovery actions have required cooperation among the United States Fish and Wildlife Service, U.S. Forest Service, Bureau of Land Management, Arizona Game and Fish Department, New Mexico Department of Game and Fish, The Nature Conservancy, and several tribal authorities.

Taxonomy and Nomenclature

Originally described by Robert Rush Miller and Carl Leavitt Hubbs in 1963, the Gila trout belongs to the genus Oncorhynchus, which includes rainbow trout and cutthroat trout species. Historically, taxonomic treatments debated its relationships with populations in the Gila River and San Francisco River drainages and compared morphology with Oncorhynchus mykiss and Oncorhynchus clarkii. Subsequent phylogenetic analyses using mitochondrial DNA and nuclear markers involved researchers affiliated with the Smithsonian Institution, University of Arizona, New Mexico State University, and the U.S. Geological Survey. Nomenclatural issues also referenced historical collectors and regional naturalists who worked in the Sonoran Desert and Chihuahuan Desert regions.

Description and Identification

Adult individuals are small to medium-sized salmonids with coloration and spotting patterns that were characterized by ichthyologists including Miller and Hubbs and later by museum curators at the American Museum of Natural History and the Museum of Southwestern Biology. Diagnostic characters were compared in curated collections at the Smithsonian Institution National Museum of Natural History and the Arizona-Sonora Desert Museum. Morphological descriptions are used in field guides produced by the American Fisheries Society, the U.S. Forest Service, and regional conservation groups to differentiate this trout from sympatric species documented in the Apache-Sitgreaves National Forests and Gila National Forest.

Distribution and Habitat

The species is endemic to headwater streams of the Gila River basin and adjacent drainages in Arizona and New Mexico, including tributaries of the San Francisco River and West Fork Gila River. Historical range descriptions appear in surveys conducted by the Bureau of Fisheries, the U.S. Fish Commission, and later inventories by the Arizona Game and Fish Department and the New Mexico Department of Game and Fish. Habitat associations involve cold, clear mountain streams within riparian corridors that intersect public lands managed by the U.S. Forest Service, Bureau of Land Management, and tribal trust lands such as those administered by the White Mountain Apache Tribe and Fort Apache Indian Reservation. Watershed-scale planning documents produced by the Environmental Protection Agency and regional watershed coalitions inform restoration on tributaries that flow into reservoirs such as Blue Ridge Reservoir and drainages near Silver City, New Mexico.

Life History and Ecology

Life-history traits have been studied by ichthyologists, university researchers at University of New Mexico and Arizona State University, and biologists from the U.S. Geological Survey. Reproductive timing, growth rates, diet composition, and interspecific interactions have been documented in peer-reviewed journals and agency reports that reference ecological principles applied by researchers at Brookfield Zoo and the Arizona Game and Fish Department hatchery programs. Ecology of the species involves trophic links with aquatic invertebrates surveyed by entomologists at the Smithsonian Tropical Research Institute methodologies, seasonal flow regimes influenced by snowmelt in the Mogollon Rim and White Mountains, and predation pressures from introduced fish species documented by the National Park Service in nearby protected areas such as Gila Cliff Dwellings National Monument.

Conservation Status and Management

The species is listed under the Endangered Species Act and has been the subject of recovery plans produced by the United States Fish and Wildlife Service. Management actions have included population monitoring by the U.S. Forest Service and state agencies, genetic management informed by laboratories at the University of California, Davis and the Arizona Game and Fish Department hatcheries, and habitat restoration funded through programs administered by the U.S. Fish and Wildlife Service and supported by nongovernmental organizations including Defenders of Wildlife and The Nature Conservancy. Legal and policy processes have involved coordination with the U.S. Department of the Interior, litigation and settlements in federal courts, and landscape-scale resource planning with the National Environmental Policy Act procedures implemented by federal agencies.

Threats and Recovery Efforts

Primary threats have included hybridization and competition with introduced brown trout and rainbow trout strains, habitat degradation from livestock grazing monitored by the Bureau of Land Management and U.S. Forest Service, catastrophic wildfires that prompted emergency actions coordinated with the Federal Emergency Management Agency and fire management programs of the National Interagency Fire Center, and diseases such as whirling disease investigated by researchers at the U.S. Geological Survey and the National Fish Health Research Laboratory. Recovery efforts have incorporated barrier construction, nonnative fish removal using methods endorsed in protocols from the American Fisheries Society, reintroductions overseen by the U.S. Fish and Wildlife Service and state departments, captive-breeding programs at facilities allied with the Arizona State University Aquatic Research Facility and regional hatcheries, and monitoring protocols developed in collaboration with universities and conservation NGOs. Collaborative landscape conservation initiatives have included partnerships with the Gila Watershed Partnership and regional watershed councils to integrate science, policy, and community engagement aimed at long-term viability.

Category:Oncorhynchus Category:Endangered fauna of the United States