The fountain darter (''Etheostoma fonticola'') is a species of freshwater

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or h ...

, a darter from the subfamily Etheostomatinae, part of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Percidae The Percidae are a family of ray-finned fish, part of the order Perciformes, which are found in fresh and brackish waters of the Northern Hemisphere. The majority are Nearctic, but there are also Palearctic species. The family contains more ...

, which also contains the

perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Per ...

es, ruffes and pikeperches. It is found in the headwaters of only two rivers in

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

, United States: the

Comal River The Comal River ( ) is the shortest navigable river in the state of Texas in the United States. Proclaimed the "longest shortest river in the world" by locals, it runs entirely within the city limits of New Braunfels in southeast Comal County. I ...

and the San Marcos River. It is generally smaller than 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, primarily the headwaters of the spring-fed San Marcos River, having been observed as far as 1.25 miles downstream, as well as the upper reaches of the Comal River in central Texas. Its geographic isolation is reflective of its incredibly specific habitation preferences which demand conditions which can only be found in these two Texas river headwaters. In these unique locations they can be observed in open areas created by a medium current at depths of 3–5 feet near the outlets of contributing spring heads with rates of flow low enough to retain a layer of percolating sand. These springs can be found adjacent to the main springs that deliver the tremendous volumes of cool, perfectly clear water that forms each river. They require a stable water temperature, within the low 70s, year round which the springs provide. These two locations are uniquely suited habitat as these ecosystems’ diversity and ultra-high densities of plant and animal life are unparalleled, with quantities exponentially surpassing each and every ecosystem within the region and all surrounding regions.

Behavior

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.

Status

They primarily occupy the sandy tops of lesser flowing springheads or flat rock surfaces absent of rooted plants, or decaying plant matter and spawn within the vibrantly abundant and healthy vegetation that thrives in these unique, pristine, springfed river systems. An extra worry for the future of fountain darters is the parasitic, non-native

trematode Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive h ...

('' 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 San Marcos is the Spanish name of Saint Mark. It may also refer to: Towns and cities Argentina * San Marcos, Salta Colombia * San Marcos, Antioquia * San Marcos, Sucre Costa Rica * San Marcos, Costa Rica (aka San Marcos de Tarrazú) ...

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 An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...

". 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.

References

* * {{Taxonbar, from=Q3756372 Etheostoma Freshwater fish of the United States Endemic fauna of Texas ESA endangered species Taxa named by David Starr Jordan Taxa named by Charles Henry Gilbert Fish described in 1886