Apache Trout

Oncorhynchus apache

Description

Also known as the Arizona trout, the Apache trout, Oncorhynchus apache, has a deep, compressed body with a large dorsal fin. It grows to a mature length of between 7-9 in (18-23 cm). The yellowish or yellow-olive back and sides are covered with uniformly spaced dark brown spots.

Behavior

The Apache trout feeds principally during the day on terrestrial and aquatic insects, taking them from the surface. Alternative food sources may include other fish, crustaceans, mollusks, and snails. After reaching three years of age, females spawn from March through mid-June, depositing eggs in several reeds. In Big Bonita Creek, fry did not emerge for 60 days, which limited growth before the severe winter set in and contributed to mortality of the young. Newly emerged fry migrate at night to reduce the risk of predation.

Habitat

The Apache trout inhabits small, cold, high gradient, fast-flowing mountain streams with boulders, rocks, and gravel substrates. The streams flow through mixed coniferous forest at altitudes above 8,250 ft (2,500 m). Water temperature ranges from 32-72°F (0-22 °C). The upper lethal temperature for the Apache trout is 73°F (23 °C), and most fish refuse to eat at temperatures above 68°F (20 °C). The severe winters typically deplete trout populations, which must recover sufficiently the following summer.

Distribution

This species was known historically from the headwaters of the Little Colorado, Salt, San Francisco, White and Black River systems in the White Mountains of eastern Arizona (Greenlee County) and western New Mexico (Catron County).

Currently, the headwaters of the White and Black river systems on the Fort Apache Indian Reservation support the greatest concentrations of the Apache trout. Streams in the Gila and Apache-Sitgreaves national forests have been rehabilitated to support reintroduced populations. Several thousand of the fish have been counted in Bonita Creek on the East Fork White River. Before reintroductions began, the range of the Apache trout was reduced to about 30 mi (48 km) of stream, less than five percent of the historic range.

Threats

Competition with introduced, non-native fishes has been the major factor in the decline of the Apache trout. Brook, rainbow, and brown trouts were introduced into many streams in the region as game fishes and expanded their populations to the detriment of the Apache trout. The Apache trout also has the ability to interbreed with the brown trout, and hybrids were spreading into many streams. Continuing hybridization would have meant the extinction of the Apache trout as an identifiable species. In the late 1970s the Fish and Wildlife Service (FWS) began a project to rehabilitate streams on the Fort Apache Indian Reservation. Ord Creek was treated repeatedly to remove introduced trout, and Apache trout from Bonita Creek were relocated there. But in spite of precautions, the brook trout reappeared in the stream the following year.

Conservation and Recovery

Biologists have erected artificial barriers in several streams to separate the species and reduce hybridization, and the Bureau of Indian Affairs and the White Mountain Apache Tribe have cooperated extensively in reintroduction efforts. In 1984, Dry Creek in the Gila National Forest was rehabilitated to accept a transplanted population of Apache trout. The stream was sampled and found to still contain trout hybrids that would dilute the genetic purity of transplanted Apaches. The project was delayed until hybrids could be removed. In 1986-87, five streams were scheduled for restoration, and in 1988 and 1990, barriers were constructed on Little Bonita Bay and three streams were restocked with pure species.

In 1986 the Williams Creek National Fish Hatch-ery succeeded for the first time in raising the Apache trout in captivity. Personnel at the facility designed an innovative feeding system that simulates natural stream conditions and automatically dispenses brine shrimp for the fry. The Hatchery hopes to raise 50,000 Apache trout fingerlings each year for re-stocking streams on the Fort Apache Reservation and Apache-Sitgreaves National Forest Service. The success of this hatchery program and continuing reintroduction efforts virtually ensure the long-term survival of the Apache trout.

Contact

U.S. Fish and Wildlife Service
Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103
http://southwest.fws.gov/

References

Alcorn, S. R. 1976. "Temperature Tolerances and Upper Lethal Limits of Salmo apache." Transaction of the American Fishery Society 105(2): 294-295.

Apache Trout Recovery Team. 1983. "Apache Trout Recovery Efforts." U.S. Fish and Wildlife Service, Albuquerque.

U.S. Fish and Wildlife Service. 1979. "Recovery Plan for the Arizona Trout, Salmo apache. " U.S. Fish and Wildlife Service, Albuquerque.