|Listed||April 30, 1986|
|Description||A small minnow.|
|Habitat||Streams and shallow rivers.|
|Food||Small invertebrates and algae.|
|Reproduction||Lays externally fertilized eggs.|
|Threats||Habitat destruction and degradation.|
The Sonora chub is a fine-scaled, medium-sized minnow. Adults are less than 3.2 in (12.5 cm) in body length, and are generally stout in appearance. They are dark-colored, with two dark lateral bands and a caudal (or tail) spot. Their small body scales are oval to rectangular in shape, and have numerous radii. During the breeding season the fins of the male develop brilliant red coloration, with a milky border on the outer margins, and their underside turns orange. The female develops a less bright coloration.
The Sonora chub feeds on small aquatic invertebrates, terrestrial insects, and algae grazed from rocks and other solid substrates. Not much is known about its breeding, but the Sonora chub probably spawns in September to October.
The Sonora chub inhabits streams and shallow rivers in dry regions. Its habitat elements include clean permanent water, pools and riffle areas, and a riparian zone of shading vegetation. It is most abundant in deeper pools.
The Sonora chub is a locally evolved (or endemic) fish that is only known from southern Arizona and nearby areas of northern Sonora state, Mexico.
Some of the original habitat of the Sonora chub was damaged by the construction of an impoundment and by the disturbance of riparian vegetation. The remaining habitat is potentially threatened by pollution by silt and nutrients, by the potential influences of recreation and mining, and by the introduction of predatory non-native fishes (such as the green sunfish, Lepomis cyanellus ) and parasites. The surviving critical habitat of the Sonora chub in Arizona is in areas of Sycamore Creek, including Yank's Spring, Penasco Creek, and an unnamed tributary. This reach of only about 4.7 mi (7.5 km) of the Sycamore Creek drainage is located within the Coronado National Forest, in Santa Cruz County, Arizona. In Mexico, it occurs in the Rio Concepcion.
Conservation and Recovery
The Sonora chub is relatively secure in its critical habitat in Arizona, due to Federal ownership and the special-use designation provided its habitats in the Coronado National Forest. However, because of the very limited amount of suitable habitat in Arizona, it is likely that significant population enhancement of the rare chub can only be accomplished by protecting parts of its critical habitat in Sonora, Mexico. Studies are being undertaken of the biology and ecology of the Sonora chub, and of the factors limiting its abundance. Human activities near its Arizona habitats are generally restricted to bird-watching, hiking, and other forms of outdoor recreation, with access limited to hiking and horseback trails. However, the canyons containing the critical habitat receive heavy visitor use, and include a trailhead parking lot for visitors. Although the chub habitat occurs within an area zoned for livestock grazing, the steep and rocky topography generally precludes this use along stream banks within the riparian zone of the critical habitat. Moreover, the U.S. Forest Service restricts grazing by domestic animals in the vicinity. The remaining portion of the Sycamore Creek Critical Habitat flows through the Gooding Research Natural Area, which was established in 1970 to protect unique species, and precludes any grazing or mineral mining. Because of its small range and population size, the Sonora chub is threatened by catastrophic population loss due to extreme weather or another cause. Consideration is being made of establishing a refugium population in a nearby fish hatchery. Neither the habitat or the chub receive official protection in Mexico.
U. S. Fish and Wildlife Service
Arizona Ecological Services Field Office
2321 West Royal Palm Road, Suite 103
Phoenix, Arizona 85021-4915
Conservation Management Institute. "Sonoma Chub 2000." Virginia Tech, Blacksburg, VA. http://fwie.fw.vt.edu/WWW/esis/lists/e252018.htm
U.S. Fish and Wildlife Service. 1986. "Endangered and Threatened Wildlife and Plants; Final Rule to Determine the Sonora Chub to be a Threatened Species and Determine its Critical Habitat." Federal Register 51: 16042-16047.