The fountain darter (Etheostoma fonticola) is a small freshwater fish found in the headwaters of only two rivers in Texas, United States: the Comal River and the San Marcos River. It is generally smaller than 3 cm (1.2 in) long and feeds on small invertebrates. It is a federally listed endangered species of the United States and is also listed as endangered by the IUCN.
Distribution and habitat
The fountain darter is known from only two locations, the headwaters of the spring-fed San Marcos River and the upper reaches of the Comal River in central Texas. It lives amongst dense aquatic foliage, especially filamentous algae, growing on a bed of decaying organic material. It favors warm backwaters with gentle movement of clear water.
The fountain darter feeds on small invertebrates. It breeds all year round and the eggs are deposited on dead leaves, stems, rocks, algae or other objects. This fish lives for one to two years.
They live in the vegetation at the bottom of clean springwater rivers, the overuse of such springs being the main reason for their depletion. An extra worry for the future of fountain darters is the parasitic, non-native trematode (Centrocestus formosanus), whose impact on the darter population is not yet known. As of 2004, only the Comal population is seriously affected by the parasite. The National Fish Hatchery and Technology Center in San Marcos keeps a reserve population of 500 adults as a hedge against a man-made or natural event wiping out the fish in the wild. The IUCN rates this species as "Endangered". Conservation efforts include encouraging people to use less water in order to maximise water flow from the springs and to keep the rivers free from trash.