Loach Minnow

Rhinichthys cobitis

Description

The slender, olive-colored loach minnow, Rhinichthys (=Tiaroga) cobitis, is the only species in its genus. It is typically less than 3.1 in (7.9 cm) in length. It is characterized by a highly oblique terminal mouth, eyes that point markedly upward, and a group of dirty white spots at the base of the dorsal and tail fins. Breeding males develop vivid red-orange markings, particularly on the belly.

Behavior

The loach minnow has not been studied thoroughly. It is omnivorous, feeding on the stream bottom on filamentous algae, zooplankton, crustaceans, and aquatic insects.

Habitat

The loach minnow inhabits streams with perennial flow and is concentrated in shallow, turbulent riffles over a cobble substrate. Recurrent flooding keeps the substrate free of silt and sediments and, because it is better adapted to strong currents, allows the loach minnow to maintain its population against encroaching non-native fishes. The semi-desert to desert region the fish inhabits is composed of plateaus, plains, basins, and many isolated mountain ranges.

Distribution

This species was once common locally throughout much of the Verde, Salt, San Pedro, San Francisco, and Gila River systems. It inhabited mainstreams and tributaries up to about 7,200 ft (2,195 m) in elevation. It is thought that the fish once inhabited about 1,750 mi (2,816 km) of stream habitat.

The loach minnow now inhabits a greatly reduced range. In Arizona it is found in Aravaipa Creek (Graham and Pinal counties), the Blue River (Greenlee County), and the White River near the confluence of the mainstem and the East Fork (Navajo County). In New Mexico it survives in the headwaters of the Gila River (Gila, Grant, and Catron Counties) and in portions of the San Francisco and Tularosa rivers and Whitewater Creek (Catron County).

The loach minnow population in the East Fork and mainstem White River on the White Mountain Apache Indian Reservation in Arizona was sampled during the summer and fall of 1989. Not much was known about this population, which was rediscovered in 1985. Researchers concluded that the loach minnow was much more abundant and widespread in the East Fork than previously thought. Still, the current range totals only about 15% of the historic range for this fish. This species occurred historically in the San Pedro River in Sonora, Mexico, but habitat there has been largely destroyed by diversion of water for irrigation.

Threats

This species' range and population size have been reduced by habitat destruction and the introduction of exotic fish species that prey upon it or compete for food and space resources.

Habitat loss has occurred as a result of river and stream alterations (dams, diversions, channelization, groundwater pumping, mining, timber production, grazing) that 1) reduce or alter stream flows (including changing flooding patterns), 2) increase and decrease water temperatures, 3) increase erosion and siltation, and 4) result in the destruction of marshes and backwaters and the removal of riparian vegetation.

The loach minnow is especially sensitive to sedimentation, reductions in stream flow, and impoundments that flood required flowing water habitats.

Other fishes in the habitat are also threatened by these changing conditions. By the late 1980s more than a third of the basin's endemic fishes were classified as endangered or threatened under federal law, and an additional 35% were considered in jeopardy by state wildlife offices.

Conservation and Recovery

In March 1994 the U. S. Fish and Wildlife Service (FWS) designated critical habitat for the loach minnow in approximately 159 miles (257 km) of portions of the Gila River in Grant and Catron Counties, New Mexico; the San Francisco and Tularosa Rivers and Dry Blue Creek, Catron County, New Mexico; the San Francisco and Blue Rivers and Campbell Blue Creek, Greenlee County, Arizona; and Aravaipa Creek in Graham and Pinal Counties, Arizona.

Large sections of the remaining inhabited streams occur on public lands. Seventy-five percent of Aravaipa Creek is protected by its designation as the Aravaipa Canyon Wilderness. Defenders of Wildlife administers portions of the headwaters as the George Whittell Wildlife Preserve. The Blue River is contained within the Apache-Sitgreaves National Forest. The Gila River flows through the Gila National Forest, which includes the Gila Wilderness, the Lower Gila River Bird Habitat Management Area, and the Gila River Research Natural Area—all managed by the Forest Service. The Forest Service also administers major portions of the San Francisco and Tularosa Rivers and Whitewater Creek. The White River population occurs on the Fort Apache Indian Reservation and has been the focus of recovery efforts conducted by the tribal council and with the Bureau of Indian Affairs.

The Middle Box Canyon on the Gila River (Grant County, New Mexico) was proposed as the site for construction of the Conner Dam and Reservoir. The Southwest New Mexico Industrial Development Corporation, the Hooker Dam Association, the Arizona Cattle Growers Association, the Arizona Mining Association, the Town of Silver City, New Mexico, and the Soil Conservation Service of New Mexico, among others, opposed federal listing of the loach minnow because it might stop or slow construction of the dam. Central Arizona Project Upper Gila Water Supply damming/impoundment plans also threatened the species. The continued conflict over water rights in the region propelled the loach minnow and other Gila River fishes into the limelight of controversy at the beginning of the twenty-first century.

Studies to determine the feasibility of reintroduction of the fish to the San Pedro River continued as funding allowed. In addition, a cooperative project (Bureau of Land Management, FWS, and Arizona Game and Fish Department) was initiated to remove exotic fishes from and prevent their movement back into Aravaipa Creek.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov/

References

Propst, D. L. 1986. "Distribution, Status, and Biology of the Loach Minnow in the Gila River Basin." New Mexico Department of Game and Fish, Santa Fe.

U. S. Fish and Wildlife Service. 1986. "Determination of Threatened Status for the Loach Minnow." Federal Register 51 (208): 39468-39478.

U. S. Fish and Wildlife Service. 1991. "Loach Minnow Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.

U. S. Forest Service. 1985. "Proposed Gila National Forest Plan." USFS Southwestern Region, Albuquerque.