Wednesday, February 08, 2017Register
 Federally Threatened and Endangered Fishes of the Edwards Aquifer

Fountain Darter
Etheostoma fonticola

Thumbnail image of Fountain Darter, courtesy of Texas Parks and Wildlife Department

 [Photo: Texas Parks and Wildlife]


Description: The fountain darter is the smallest of all darters, reaching only 1.4 inches (3.5 cm) in length. It is olive and white, with dark spots scattered throughout its dorsal and ventral surfaces. The males exhibit red, black, and clear banding on their first dorsal fin and both males and females display light brown banding on their 2nd dorsal fin.

Life History: The fountain darter breeds in pairs year round, peaking in August and late winter. Females are mature at 3.5 months and lay 760 eggs at a time, on average, on filamentous algae and plants. Fountain darters feed mostly during the day on immature insects (mayfly and "true" fly larvae) and small crustaceans including water fleas, copopods, and amphipods.

Habitat: The fountain darter lives in the thermally stable (70-75 degrees F [21-24 deg C]) freshwater lakes, springs, and rivers associated with the Comal and San Marcos rivers in the Edwards Aquifer. It prefers to live in murky, densely vegetated waters among botto-growth plant species such as algae, hydrilla, and water primrose.

Distribution: Etheostoma fonticola is found in Spring Lake, San Marcos Springs, and the upper portion of the San Marcos River in Hays County, TX. It is also found in Landa Lake, Comal Springs, and the entire length of the Comal River in Comal County, Texas.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do not represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

 Federally Designated Critical Habitat for the Fountain Darter (Etheostoma fonticola) [Figure: Houston Advanced Research Center using US FWS data]

Federally Designated Critical Habitat for the Fountain Darter (Etheostoma fonticola) [Figure: Houston Advanced Research Center using US FWS data]. Click on map for larger image.

Status: The fountain darter is a state and federally listed (1978) endangered species. There is a refugium for this species at the San Marcos National Fish Hatchery and Technology Center. Although this species is robust within its habitat, it is considered endangered due to the population's sensitivity to a single major event, such as drought. The fountain darter is reliant on the aquatic vegetation in the San Marcos and Comal Rivers. A reduction in the water quality or quantity in these springs or rivers that may affect the growth of these aquatic plants, has profound effect on the fountain darter population. The Edwards Aquifer Authority defines prime habitat for the fountain darter at flows >150 cfs in Comal Springs and associated river ecosystem and >100 cfs at San Marcos Springs and associated river ecosystem. The US Fish and Wildlife Service defines "take" for this species at flows of <200 cfs for the Comal system and <100 cfs for the San Marcos system. There is a legitimate risk to the fountain darter population at flows of 80 and 60 cfs in the Comal and San Marcos Rivers, respectively. The fountain darter is also threatened by exotic species and parasites.

Resources:

US Fish and Wildlife Service, Critical Habitat Final Rule

Edwards Aquifer Authority, Draft Edwards Aquifer Habitat Conservation Plan

Schenck, John, R. and Whiteside, B.G. 1976. Distribution, Habitat Preference and Population Size Estimate of Etheostoma fonticola. Copeia. Vol, 1976, No. 4, pp 697-703.

 

San Marcos Gambusia
Gambusia georgei

Thumbnail image of San Marcos Gambusia, courtesy of Texas Parks and Wildlife Department

[Photo: Texas Parks and Wildlife]

Description: The San Marcos gambusia is a small fish of the family Poeclilidae. The San Marcos gambusia is 1 of 3 species of Gambusia in the San Marcos River, although it has by far the most limited range. It is very similar in appearance to the western mosquitofish (Gambusia affinis). It is 1 inch (2.5 cm) long, with a dark stipe on the upper edges of its dorsal fin, and dark bars around the eyes. This fish has yellowish fins (yellowish-orange around the gonopodium of adult males) and a bluish sheen around the head in adult females.

Life History: The male San Marcos gambusia possesses a gonopodium (tube structure on anal fin) that is uses to transfer sperm to female during breeding. The San Marcos gambusia gives birth to live young and has been shown to produce clutch sizes from 12-60 in captivity. Relatively little is known about the food consumption of the San Marcos gambusia, although it is assumed to feed on insect larvae and other invertebrates.

Habitat: The San Marcos gambusia prefers partially shaded habitats with overhanging vegetation in shallow, sparsely vegetated, relatively still waters adjacent to fast flowing water. Constant water temperature (70-72 degrees F [21-22 deg C]) is extremely important to this fish and it occupies the upper portions of the San Marcos River and San Marcos Springs where temperature is constant. The San Marcos gambusia prefers muddy bottoms without much siltation.

Distribution: Gambusia georgei is distributed along the thermally constant sections of the San Marcos River which includes San Marcos Springs and the upper gravelly portion of the San Marcos River down to 0.5 miles below the Interstate 35 Bridge, in Hays County, Texas.

The map below depicts the critical habitat for this species, as designated by the US Fish and Wildlife Service pursuant to the Endangered Species Act.

NOTE: No warranty is given, expressed or implied, as to the accuracy, reliability, or completeness of these data. Data do no represent a legal description of the critical habitat boundary; refer to the textual description in the appropriate final rule for this species as published in the Federal Register.

Federally Designated Critical Habitat for the San Marcos Gambusia (Gambusia georgei) [Figure: Houston Advanced Research Center using US FWS data]

Federally Designated Critical Habitat for the San Marcos Gambusia (Gambusia georgei) [Figure: Houston Advanced Research Center using US FWS data]. Click on map for larger image.

Status: The San Marcos gambusia is a state and federally listed (1980) endangered species. The San Marcos gambusia was last collected in 1983. This species is considered very rare, and may possibly be extinct, largely to reduced habitat and hybridization with the western mosquitofish. Slight changes in the San Marcos River channel, reduction in spring flow, or surface pollution could severely injure this population. The flow considered as "take" by the US FWS is 100 cubic feet per second.

Resources:

Hubbs, Clark and Alex E. Peden. 1969. Gambusia georgei sp. nov. from San Marcos, Texas. Copeia, Vol. 1969, No., pp. 357-364.

Texas Parks and Wildlife, Endangered Species of the Edwards Aquifer

Texas Parks and Wildlife, San Marcos Gambusia Profile

US Fish and Wildlife Service, Critical Habitat Listing

US Fish and Wildlife, Endangered Species Listing

US Fish and Wildlife Service, San Marcos Recovery Plan

Toothless Blindcat
Trogloganis pattersoni

Thumbnail image of Toothless Blindcat, courtesy of Texas State University at San Marcos

[Photo: Texas State University at San Marcos]

Description: The toothless blindcat, of the family Ictaluridae, is 1 of 2 cave-dwelling (troglobotic) catfish in North America. The toothless blindcat is the only member of the Trogloganis genus, distinguished from other Ictalurids by its many cave-adapted features. They can grow up to 4.1 inches (10.4 cm) long, with a weight of 0.6 ounces (16 grams). This catfish has large nostrils, a small, red toothless mouth with thin lips, well-developed barbels, and a snout which overhangs its mouth. This catfish has many cave-adapted features. These include its lack of eyes, pale white or pinkish body, a well-developed lateral line, and lack of an air bladder. The absence of an air bladder, which is present in most fish, gives the toothless blindcat the ability withstand the immense pressure in the deep caves it inhabits. This bladder has been replaced by an abundance of fatty tissue which gives it buoyancy.

Life History: The toothless blindcat does not have any external distinguishable sex characteristics. Females have frequent egg production and are mature when they reach greater than 2.4 inches (6 cm) in length. This catfish is herbivorous, utilizing a well developed olfactory system to find food, as well as utilizing vibrations detected by its lateral line. These fish feed on the detritus in mud which is consumed by sucking up mud on the bottom of its habitat.

Habitat: The toothless blindcat lives in the subterranean waters of Edwards Aquifer at depths of 1000-1900 feet (305-582 m) and temperatures of 80 degrees F (27 deg C). This fish lives in habitats under great hydrostatic pressure.

Distribution: Trogloganis pattersoni is restricted to the San Antonio Pool of Edwards Aquifer in Bexar County, TX (256,000 acres [103,600 ha]). The fish has been collected at five artesian wells in the Southern part of Bexar County.

The map below depicts the area where this species has been reported (according to literature review).

Reported Species Distribution of the Toothless Blindcat (Trogloganis pattersoni) [Figure: Houston Advanced Research Center]

Reported Species Distribution of the Toothless Blindcat (Trogloganis pattersoni) [Figure: Houston Advanced Research Center]. Click on map for larger image.

 Status: The toothless blindcat is a state listed threatened species. The population is abundant within its range; although due to their deep cave habitat, observations of the toothless blindcat can be difficult. This population is sensitive because its range is very small and a drop in groundwater could pose a risk to this species.

Resources:

Edwards Aquifer Research and Data Center, Toothless Blindcat Status

Texas State University at San Marcos, Biology Department, Texas Freshwater Fishes, Toothless Blindcat Species Profile

Widemouth Blindcat
Satan eurystomus

Thumbnail image of Widemouth Blindcat, courtesy of Texas State University at San Marcos

[Photo: Texas State University at San Marcos]

Description: The widemouth blindcat, of the family Ictaluridae, is 1 of 2 cave-dwelling (troglobotic) catfish in North America. The widemouth blindcat is the only member of the Satan genus, distinguished from the rest of the Ictalurids by its many distinctive cave-adapted features. The widemouth blindcat can grow up to 5.4 inches (13.7 cm) long with a weight of 0.95 ounces (27 grams). This catfish has a broad flat head and snout, small nostrils, well-developed teeth, strong jaws of normal shape and size, and thick lips. It has well-developed barbels (larger than toothless blindcat) which it uses for taste and touch. This catfish has many cave-adapted features. These include its lack of eyes, pale white or pinkish body, a very well-developed lateral line, and lack of an air bladder. The absence of an air bladder, which is present in most fish, makes the widemouth blindcat able to withstand the great pressure in the deep caves it inhabits. This bladder has been replaced by an abundance of fatty tissue for buoyancy.

Life History: The widemouth blindcat is an opportunistic predator and the top carnivore in the subterranean Edwards Aquifer ecosystem. It is believed that it will eat anything that comes into contact with its mouth and finds food using vibrations detected by its lateral line. This is in addition to the touch and taste sensations provided by its over-developed barbels. Its diet consists of detritus, crustaceans, and possibly the toothless blindcat.

Habitat: The widemouth blindcat lives in the subterranean waters of the Edwards Aquifer at depths of 1000-1900 feet (305-582 m) and temperatures of 80 degrees F (27 deg C). This fish lives in habitats under great hydrostatic pressure.

Distribution: Satan eurystomus is restricted to the San Antonio Pool of Edwards Aquifer in Bexar County, TX (256,000 acres [103,600 ha]). The fish has been collected at five artesian wells in the Southern part of Bexar County.

The map below depicts the area where this species has been reported (according to literature review).

Reported Species Distribution of the Widemouth Blindcat (Satan eurystomus) [Figure: Houston Advanced Research Center]

Reported Species Distribution of the Widemouth Blindcat (Satan eurystomus) [Figure: Houston Advanced Research Center]. Click on map for larger image.

Status: The widemouth blindcat is a state listed threatened species. The population is abundant within its range although, due to the depth of its habitat within the aquifer, it is difficult to sample for them. This population is sensitive due to its restricted range (San Antonio pool), thus a drop in groundwater could pose a risk to this population. This catfish is the top predator in the Edwards Aquifer ecosystem; which makes it useful as an indicator of water quality. This is especially true for the widemouth blindcat because it collects toxins in its extensive fatty deposits.

Resources:

Edwards Aquifer Research and Data Center, Widemouth Blindcat Status

Texas State University at San Marcos, Biology Department, Texas Freshwater Fishes, Widemouth Blindcat Species Profile


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