Snail Darter - Ecology

Ecology

The snail darters are found in gravel shoals free of silt and aquatic plants, with moderate to strong currents, and moderate depths. The substrate generally consists of dark micaceous sand, with little to no silt, and 25 to 50 percent of the area scattered with gravel. Agricultural development has also affected the water clarity, and silt run-off causes problem for reproduction and migration. In 1976, the winter temperature ranged from 5° to 12°C, and summer temperature averaged near 18°C in the Little Tennessee River. These temperature fluctuations are due to impoundments, resulting in colder water when the dam is discharging and warming water when flow is diminished. Current velocities ranged from a moderate 0.25 m/sec to nearly 0.7 m/sec. The snail darter actively feeds in spring and winter with a diet consisting of 60% small gastropods (5mm or less in diameter) and other prey such as caddisflies, midges, and blackflies. Snails are the preferred food source until late spring when they outgrow the gape size of the fish, resulting in a diet change to insect larvae. The most effective predator on adult snail darters is Cottus carolinae while Salmo trutta, Morone chrysops, Sizostedion canadense, and other darters would prey on eggs and juveniles. The snail darters’ dorsal patterns and coloration allow the fish to camouflage with the substrate to avoid detection from predators. Burrowing behavior also is a defense mechanism and can help conserve energy for the current.