Percina tanasiSnail Darter

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Geographic Range

Once limited to the Tennessee River and tributaries, the darter now also lives in connected reservoirs. In 1975 and 1976, a population was transplanted to the Hiwassee River, and is doing well.

Habitat

Moderately flowing, vegetated streams with sandy bottoms and wide shoals for spawning.

  • Aquatic Biomes
  • rivers and streams

Physical Description

Reproduction

Between January and mid-March, adult snail darters spawn on river shoals. Eggs deposited in gravel or on rocks hatch in 15 to 20 days.

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    4 years
    AnAge

Behavior

Newly hatched snail darters drift downstream, later returning to the shoal areas. They are short-lived, with a maximum age of five or six years.

Communication and Perception

Food Habits

The snail darter eats small invertebrates, with aquatic snails making up about 60 percent of the darter's food, with some variation among seasons.

Economic Importance for Humans: Positive

By traditional economics, the snail darter has no significant positive economic importance. However, when listed as an Endangered Species in 1975, it was the focus of a Supreme Court case that set the precedent for protecting endangered species, regardless of cost.

Economic Importance for Humans: Negative

The snail darter case caused the Tellico Dam project to be halted. In response, Congress amended the Endangered Species Act to include a "God Squad", which could overrule protecting a species under enormous economic sacrifice. The committee got its name because it can play "God" and allow species to go extinct for economic reasons.

Conservation Status

Originally classified as Endangered on October 9, 1975. Reclassified as Threatened on July 5, 1984. A number of new populations have been found, increasing the number of known individuals.

Other Comments

The snail darter has become a symbol for conservationists and anti-environmentalists alike. Eventually, an act was passed by Congress requiring completion of the Tellico Dam. The act went on record as being the first offical U.S. government decision to extirpate a species. Only because of a successful transplant by the Fish and Wildlife Service does the snail darter still exist. The animal is a reminder of the relative importance of conserving biodiversity compared to development in the eyes of the United States government.

Contributors

Noah Hall (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

tactile

uses touch to communicate

References

Lowe, David W., John R. Matthews. and Charles J. Moseley. The Official WWF Guide to Endangered Species of North America. Volume 2. Washington, D.C.: Beacham Publishing, Inc., 1990. 921- 923.