Relict Darter

Etheostoma chienense

Description

The relict darter is one of the 10 recognized species in the Etheostoma squamiceps complex. It is a small (2.5 in; 6.4 cm) fish. The general body coloration of females and nonbreeding males consists of brown mottling on a light tan background. The dorsum coloration is variable, usually similar to the sides, but sometimes paler and crossed by six to eight small dark brown saddles. The venter is white and unmarked. The head has dark pre-and postorbital bars.

The most distinctive aspects of the relict darter are features of pigmentation and morphology of the dorsal fins of breeding males. The species can be distinguished with certainty only by examination of breeding males. Bright breeding colors do not develop. Breeding males are gray or dark brown on the dorsum and sides with light tan on the venter. The head and nape are greatly swollen and black, and the dark coloration obscures the nonbreeding pattern. Territorial and spawning males have alternating white and black bars on the side of the body. The first dorsal fin is black, except for a clear basal band, and has a small white knob on the tip of each spine; a small, clear triangle behind each knob that narrows into a thin, clear margin; and a small, clear teardrop posterior to each spine located two-thirds the distance from the base of the fin to its margin. The caudal fin has a thin, clear margin and five to nine dark bands alternating with an equal number of clear to yellow bands that become increasingly wider and darker distally. The middle spot on the caudal fin base is darker than the other two fins. The anal and pelvic fins are dusky to black with narrow, clear margins.

Behavior

There is no published information on the reproduction of the relict darter, but it is assumed to be the same as other members of the genus. Males and females mature at one year of age at about 1.6 and 1.4 in (4.1 and 3.6 cm) standard length, respectively, but most males apparently do not spawn until their second year. Spawning occurs from late March to early June. Eggs averaging about 0.7 in (1.8 cm) are deposited on the undersides of submerged objects, usually flat stones. In the case of the relict darter, eggs are attached frequently to the undersides of sticks or logs; other related species spawn on the undersides of slab rocks. The female and male invert briefly during egg-laying and then both return to an upright position. Several females may spawn with a single male, and nests may contain as many as 1,500 eggs. The eggs are guarded by the male. Incubation periods range from about 125 hours at 71.6-78.8°F (22-26°C) to 270 hours at 64.4-71.6°F (18-22°C).

Habitat

Adults are concentrated in headwaters and creeks in quiet to gently flowing pools, usually over gravel mixed with sand and under or near cover such as fallen tree branches, undercut banks, or overhanging riparian vegetation.

Distribution

The relict darter is endemic to the Bayou du Chien system, a Mississippi River tributary, in extreme western Kentucky. This darter was "fairly common" in the high gradient reaches of Bayou du Chien in the early 1970s. In 1991 individuals were collected at five sites, but abundant at only two sites (18 individuals were collected at one site and 46 at another). The other three sites yielded a total of only eight relict darters. Only one spawning area has been located—in a small tributary stream located in Graves County.

Threats

The most signicant factors in the relict darter's decline have likely been the poor land use practices in the area, which foster damaged silt to the creek, and canalization of the Bayou du Chien, which has significantly altered the darter's habitat. Improper pesticide use might also be a factor in the species' decline.

The Bayou du Chien system has been extensively channelized. Much of the streams' sinuosity was eliminated, undercut banks were lost, stream bank vegetation and in-stream cover were removed, and some smaller streams now flow only intermittently. This massive alteration of the relict darter's habitat reduced both relict darter numbers and the amount of suitable habitat. Aside from past channelization impacts, the area is extensively farmed and much of the watershed has been deforested. These alterations result in a fairly high silt load within the Bayou du Chien system that continues to degrade the habitat and further impacts the species. Because the relict darter inhabits only short stream reaches, it is vulnerable to extirpation from accidental, toxic chemical spills. This is especially true of the only known relict darter spawning site. Additionally, because the relict darter population has been drastically reduced in size, the species long-term genetic viability is questionable.

Conservation and Recovery

To save the relict darter, all existing state and federal legislation and regulations must be enforced. Relict darter research needs include: life history information (spawning season and behavior, habitat requirements, age and growth, and food habits); propagation and reintroduction techniques; and habitat improvement techniques. Management needs include: reestablishing spawning subpopulations in other tributaries; promoting the safe use of pesticides by local farmers; enforcing existing federal and state laws relating to water quality, and monitoring the species especially at spawning areas. Because suitable habitat has been reduced, especially spawning habitat, a program to improve habitat is one of the most important management needs. Additionally, management is needed to restore some of the species' habitat through repair of riparian habitat and control of nonpoint source pollution.

Contacts

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

U. S. Fish and Wildlife Service
330 Ridgefield Court
Asheville, North Carolina 28806
Telephone: (704) 665-1195

References

Page, L. M., P. A. Ceas, D. L. Swofford, and D. G.Buth. 1992. "Evolutionary Relationships with the Etheostoma squamiceps Complex (Percidae: Sub-genus Catonotus ) with Descriptions of Five New Species." Copeia 1992 (3):615-646.

U. S. Fish and Wildlife Service. 1993. "Determination of Endangered Species Status for the Relict Darter." Federal Register 58 (246):68480-68486.

Warren, M. L. 1991. "Survey of the Relict Darter (Etheostoma (Catonotus ) sp. cf E. neopterum )." Final Report Submitted to the U. S. Fish and Wildlife Service, Asheville, NC. 33 pp.

Webb, D. H., and M. E. Sisk. 1975. "The Fishes of West Kentucky. III. The Fishes of Bayou de Chien." Transactions of the Kentucky Academy of Science. 36:63-67.