Slackwater Darter

Etheostoma boschungi

Description

The slackwater darter, Etheostoma boschungi, was recently placed in a new subgenus, Ozarka. This group of medium-sized darters range from 1.6-3 in (4-7 cm) in length. The slackwater darter is distinguished from members of its group by a bold blue-black bar under the eyes and three prominent dark dorsal saddles.

Behavior

The slackwater darter feeds on insects and small crustaceans. Its life span is probably no more than three years.

Spawning usually begins in early March but may vary from year to year depending on temperature and rainfall. Water temperature must be warmer than 57°F (14°C), and rainfall must be heavy enough to lift adults into their spawning grounds. Each female attaches 100-300 eggs to Juncus and Eleocharis plants. Males aggressively defend egg-laden clumps of plants. Fry develop in late March and April and return to streams in late April or early May. Depending on rainfall and temperature conditions, the spawning activities progress as follows: November to January: adults aggregate for spawning migration; nuptial colors and gametes begin developing; there is strong evidence that individuals assemble in particular places downstream of the breeding site so that they can make their surge to the spawning area in unison; January to the end of February: the spawning migration occurs and nuptial colors and gametes are fully developed; late February to the end of March: males establish territories, court females, and completes spawning; April: larvae develop in the breeding habitat; May: larvae leave the breeding habitat.

Habitat

The slackwater darter has distinct breeding and non-breeding habitats. It normally inhabits small to moderate, slow-flowing, upland streams, no more than 40 ft (12 m) in width and shallower than 6.6 ft (2 m). In wider streams, darters tend to gather in sluggish water beneath overhanging banks. It avoids riffles and rapids, and prefers substrates of gravel combined with silt or mud. It has not been observed over clean gravel substrates or in swift currents. It shows some preference for accumulated detritus, such as twigs and well-decayed leaves, but not large concentrations of newly fallen or compact leaves. Migration is not impeded by moderate riffles or shallow water, and the species is adaptable to changes in the oxygen level of the water as it changes during the summer.

Ready-to-spawn darters are lifted by heavy spring rains into seepage areas in open fields, pastures, and woods, where they spawn. Water in these seepages is typically no more than 3 in (8 cm) deep. The stream level must rise sufficiently to give spawning individuals access to the breeding grounds, whose elevations are between 620-840 ft (189-256 m).

Distribution

The remaining populations of the slackwater darter are probably remnants of a more widespread and continuous distribution throughout the smaller streams of the Tennessee River basin. Populations are currently found in five tributaries of the south bend of the Tennessee River: Buffalo River and Shoal Creek in Lawrence County, Tennessee; and Flint River (Madison County), Swan Creek (Lime-stone County), and Cypress Creek (Lauderdale County), Alabama. In 1984 the population was estimated at 3,600 in Cypress Creek, where the heaviest concentration of slackwater darters is found. Other streams may support only a few hundred of the fish. Biologists consider the population dangerously low.

Threats

The slackwater darter's breeding habitats have been in slow but steady decline for the past 200 years. Heavy use of groundwater for agriculture and human consumption has caused water tables to fall throughout the region, drying up many seepage areas that were historically used for spawning. Numerous spawning seepages have been diked to form agricultural ponds, and increased agricultural clearing has significantly increased siltation in the habitat.

Spreading urbanization is a potential threat to the habitat because of alteration in drainage that affects groundwater levels. The quality of groundwater is being degraded by pollutants, including insecticides, herbicides, fertilizers, industrial and chemical wastes from sewage lines and septic tanks seepage, and stockyard runoff. Because the breeding grounds are so limited, even a small spill could exterminate a breeding population. Much of the year the breeding grounds are too wet for crops, and so these areas are being turned into farm fish ponds. Probably many breeding sites have been eliminated by these farm fish ponds. Beavers have also dammed spawning streams and eliminated breeding areas.

Conservation and Recovery

The slackwater darter's specialized breeding habitats for the Buffalo and Flint Rivers, and Shoal and Swan Creeks, have not been fully mapped. This was the first task established by the U. S. Fish and Wildlife Service (FWS) Recovery Plan. The FWS hopes to purchase breeding sites or obtain management easements from private owners to protect breeding areas on at least three of currently inhabited streams. Without protection, it is feared that most seepage areas will disappear completely in the next 20 years.

Contact

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

References

Page, Lawrence M. 1983. Handbook of Darters. T.H.F.Publishers, Neptune City, New Jersey.

U.S. Fish and Wildlife Service. 1984. "Slackwater Darter Recovery Plan." U.S. Fish and Wildlife Service, Atlanta.

Wall, B. R., and J. D. Williams. 1974. "Etheostoma boschungi, a New Percid Fish from the Tennessee River Drainage in Northern Alabama and Western Tennessee." Tulane Studies in Zoology and Botany 18(4):172-182.

Williams, J. D., and H. W. Robison. 1980. "Ozarka :A New Subgenus of Etheostoma." Brimleyiana 4:149-156.