Bayou Darter

Etheostoma rubrum

Description

Only about 1.9 in (5 cm) long at maturity, the bayou darter, Etheostoma rubrum, displays russet markings on a field of dusky yellow. The back is a darker brownish yellow. Both males and females have a prominent double spot on the tail fin and a dark bar under the eyes. Males are decidedly larger than females.

The bayou darter is the second-smallest species in the subgenus Nothonotus, the smallest being the Tippecanoe darter (E. tippecanoe ) found in the Ohio River system. The bayou darter is closely related to the yellow cheek darter (E. moorei ) found in the Devil's Fork and Little Red River of Arkansas' White River system.

Behavior

The bayou darter spawns in mid-summer when it is about two years old, and probably lives three years. Darter fry hatch at the same time that mayfly larvae emerge in the same riffle habitat, and darter minnows are thought to feed almost exclusively on mayfly larvae. Adults feed on insects, small crustaceans, and plant matter.

Habitat

The watershed, where this darter is found, arises in coastal hills with elevations around 450 ft (137 m). From their sources, the creeks fall in steps to the coastal plain, where water flow has eroded through deposits of gravel, interspersed with sand. This has resulted in numerous gravel or sandstone riffles of moderate to swift current, which seem to be preferred by the bayou darter. The water in these riffles is typically only about 6 in (15 cm) deep.

Distribution

The bayou darter was first described in 1966 from specimens collected at Mississippi Highway 18 Bayou Pierre crossing. This species is probably endemic to the Bayou Pierre and its five major tributaries, a watershed that drains about 965 sq mi (2,500 sq km) of western Mississippi. The source of Bayou Pierre is a small seep near Brookhaven in Lincoln County.

The bayou darter has been found in Bayou Pierre and three of its tributaries (White Oak Creek, Foster Creek, and Turkey Creek). Range of the bayou darter seems to be limited upstream by waterfalls and downstream by the gradual loss of suitable riffle habitat. The largest concentration of bayou darters is in sections of Bayou Pierre and Foster Creek north of state highway 548 in Copiah County. Researchers consider the population to be limited but also report that they have not observed any significant decline in numbers in recent years. As of 1990, the U. S. Fish and Wildlife Service (FWS) considered the population stabilized, and the potential for recovery is good.

Threats

The major limitation on bayou darter numbers is its dependence on its specialized habitat—sand and gravel riffles. Some sand and gravel mining already occurs in the area, directly threatening the bayou darter's habitat. Agriculture is widespread in the region, particularly along portions of Turkey Creek and lower Bayou Pierre. In some places, streambank vegetation has been cleared, causing severe erosion and siltation. Nearby petroleum exploration may also pose some threat to water quality.

Conservation and Recovery

In the 1970s the Soil Conservation Service conceived the Bayou Pierre Watershed Project to dredge and straighten stream beds, build flood walls and dikes, and construct 24 dams to provide recreational pools. The project would have eliminated most of the bayou's habitat from the affected streams. After consultation with the FWS, the project's sponsors eliminated the dredging, channel work, and dams, and agreed to evaluate the effects of flood wall construction on downstream water quality. An agreement between the FWS and the Soil Conservation Service allowed construction of one dam on Turkey Creek above the Turkey Creek Falls.

The state of Mississippi has listed the darter as Endangered, providing it some protection from collection. It has been noted that clear-cutting along the stream banks could contribute to erosion and alter the water temperature. Timber companies operating in the area have been careful to provide buffer zones along streams, such as Bayou Pierre, as part of their stated policy of conserving riparian habitat.

In the 1990 revised Recovery Plan, the FWS included plans to implement a study on the fluvial geomorphic processes operating in Bayou Pierre. The species will be considered for delisting if recovery efforts are deemed successful, based on criteria that include a stable or increasing population (and habitat) over at least a 10-year period in Bayou Pierre and Foster Creek; evidence of the continued existence of the species in White Oak and Turkey Creeks; data on fluvial geomorphic processes operating in the Bayou Pierre system which supports the delisting of the species; an established continuing plan of periodic monitoring of population trends and habitat suitability; and continued protection of the darter's habitat. The 1990 revision listed the darter's population status as stable, and the FWS has given the species a recovery priority rating of 8C, which means the degree of threat to this species is moderate and the recovery potential is high.

Contact

Regional Office of Endangered Species
U.S. Fish and Wildlife Service
1875 Century Blvd., Suite 200
Atlanta, Georgia 30345
http://southeast.fws.gov/

References

Deacon, J. E., et al. 1979. "Fishes of North America:Endangered, Threatened, or of Special Concern." Fisheries 42:29-44.

U.S. Fish and Wildlife Service. 1983. "Bayou Darter Recovery Plan." U.S. Fish and Wildlife Service, Atlanta.

U.S. Fish and Wildlife Service. 1990. "Endangered and Threatened Species Recovery Program Report to Congress." U.S. Fish Wildlife Service, Washington, DC.