status: Vulnerable, IUCN Endangered, ESA
range: USA (Texas)
Description and biology
The fountain darter is a small fish that does not grow more than 1.5 inches (3.8 centimeters) long. It is reddish-brown in color with a series of dark, horizontal, stitchlike lines along its sides. Fine specks and dark blotches cover its back. Three dark spots appear at the base of its tail, and dark bars appear below, behind, and in front of its eyes. The black dorsal (back) fin has a broad, red band.
The fountain darter feeds during the day on aquatic insect larvae and small crustaceans, such as crabs or shrimps. It prefers only live, moving prey. The darter remains perfectly still, waiting for its prey to move within 1 inch (2.5 centimeters) of it, then it quickly darts or moves towards its prey (hence its common name, darter).
Female fountain darters can spawn, or lay eggs, throughout the year, but peak spawning takes place in late spring and again
in August. After a female lays her eggs on vegetation such as moss or algae, she abandons the nesting site and never returns.
Habitat and current distribution
The largest population of fountain darters is found in a 2-mile (3-kilometer) area of the San Marcos River in Hays County, Texas. A reintroduced population is found in the upper Comal River in Comal County, Texas. In the mid-1970s, biologists estimated that about 103,000 darters inhabited the San Marcos River. They believe, however, that the current population has increased slightly. The population in the Comal River is thought to be smaller than that of the San Marcos River.
Fountain darters prefer clear, clean water with abundant vegetation along the stream bed. Water temperature of their habitat is usually just above 70°F (21°C).
History and conservation measures
The fountain darter was first identified in the San Marcos and Comal Rivers in the late nineteenth century. In the mid- 1950s, the fish disappeared from the Comal River when it was reduced to isolated pools. Droughts in the region had forced the Comal Springs, which feed the river, to stop flowing for a time. In 1975, biologists took a number of darters from the San Marcos River and reintroduced them to the Comal River.
Swimmers and other recreational users of the San Marcos River often disturb the algae mats used by the darters for nesting sites. However, the primary threat to the fish is the growing human population in the area and its increasing demand for water. This demand is depleting the underground aquifer (an underground layer of sand, gravel, or spongy rock that collects water) that feeds the fountain darter's river habitat.
State and local agencies that manage the use of the aquifer are developing water-use plans to help maintain spring flows to the rivers, and thus save the darter's habitat.
DID YOU KNOW?
The snail darter (Percina tanasi), a member of the same family as the fountain darter, was at the center of one of the most controversial environmental battles waged in the United States. In 1973, a zoologist discovered this species of darter in the lower portion of the Little Tennessee River in Loudon County, Tennessee. At that time, the Tellico Dam was being built just downstream from this area. If completed, the dam would flood and completely destroy the darter's habitat.
Environmentalists quickly fought to have the snail darter placed under government control. In 1975, the fish was officially categorized as endangered on the Endangered Species List. Since federal law prohibits any federal projects that might harm endangered species, all work on the Tellico Dam came to an immediate halt. The case then went to court, and in 1978, the U.S. Supreme Court sided with the environmentalists. Just one year later, however, the U.S. Congress passed a bill with an attachment allowing the dam to be built. President Jimmy Carter refused to veto the measure, and the Tellico Dam was completed in November 1979. All of the snail darter's critical habitat was wiped out.
While the case was being fought, biologists (people who study living organisms) transplanted darters into the main stem of the Tennessee River and a few of its tributaries (smaller streams leading into a larger one). Luckily, the fish adapted and began to breed. By 1984, the species had recovered enough to be downlisted to threatened on the Endangered Species List. It remains at that category to this day.