San Marcos River, just below mouth of Blanco River, Texas (Jordan and Gilbert 1886).
Etymology/Derivation of Scientific Name
Etheostoma, from the Greek etheo, “to strain,” and stoma, mouth”
(Pflieger 1997); fonticola: means fountain dweller. Before being inundated by a small dam and lake, the main spring at San Marcos was described as emerging like a fountain from a limestone basin (Keuhne and Barbour 1983).
Alvarius fonticola Jordan and Gilbert 1886.
Maximum size: Reaching 35.5 mm SL, it is the smallest of all darters (Page and Burr 1979).
Coloration: Sides with large black rectangular blotches (Hubbs et al. 1991). Body is olive dorsally, white vetrally, with scattered dark spots dorsally and laterally and sometimes with 7-8 dusky dorsal saddles; midlateral row of greatly elongated dark blotches and often 3 small dark basicaudal spots; dark orbital bars present (Page 1983); pronounced black, clear, red, clear, and black bands on the 1st dorsal fin of males (Schenck and Whiteside 1977b), while that of the female is mostly clear; 2nd dorsal and caudal fins have light brown banding, while other fins are clear or with melanophores along the rays. Fins of breeding male much darker than those of female, especially 1st dorsal, pelvics, and anal, and black and red bands in the 1st dorsal fin intensify (Page 1983).
Counts: 6 dorsal fin spines (occasionally 7); 1 anal fin spine; less than 77 scales in lateral line; fewer than 6 lateral line scales with pores (Hubbs et al. 1991). Page (1983) listed counts for Etheostoma fonticola including: lateral scales 31-37 (32-34), 0-6 (2-3) pored; scales above lateral line 3-5; scales below lateral line 5-7; transverse scales 9-12 (11); scales around caudal peduncle 14-17 (16); dorsal spines 6-8 (7); dorsal rays 10-13 (10-11); pectoral rays 8-11 (9-10); anal rays 5-8 (6-7); 6 branchiostegal rays; vertebrae 32-33.
Body shape: Body depth contained in standard length less than seven times (Hubbs et al. 1991). Keuhne and Barbour (1983) described this darter as minute, but robust.
External morphology: Lateral line short; scales on belly normal (a narrow naked band may be present on midline); preopercle smooth or weakly serrate; upper jaw not extending as far as to below middle of eye (Hubbs et al. 1991). Breeding tubercles develop on anal and pelvic rays of male. Pelvic fins of male have expansive lateral flaps. Bilobed genital papilla of female is swollen and much larger than small flap-like papilla of the male (Page 1983).
Distribution (Native and Introduced)
Texas distribution: Endemic to thermally constant (21-24 degrees C; Bonner and McDonald 2005) springs and the upper San Marcos (Hays Co.) and Comal (Comal Co.) rivers in central Texas; original population in the Comal River was extirpated in the mid-1950’s when Comal Springs ceased to flow (Hubbs et al 1991); a population from San Marcos was reintroduced into Comal Springs in 1975 (Schenck and Whiteside 1976). San Antonio Bay drainage unit (Warren et al. 2000).
Abundance/Conservation status (Federal, State, NGO)
Populations in southern drainages are considered endangered (Warren et al. 2000). Deacon et al. (1979) listed the species as endangered due to vulnerability of entire population to a single catastrophe. San Marcos River population estimated to number 102,966 individuals (Schenck and Whiteside 1976). Upper Comal River population estimated to number 168,078 individuals (Linam et al. 1993).
Macrohabitat: Thermally constant (21-24 degrees C; Bonner and McDonald 2005) springs and the upper San Marcos (Hays Co.) and Comal (Comal Co.) rivers in central Texas (Hubbs et al. 1991).
Mesohabitat: Critical thermal temperature for adult fish 34.8 degrees C (Brandt et al. (1993). Usually occurs in dense beds of Vallisneria, Elodia, Ludwigia and other aquatic plants that flourish in the San Marcos and Comal Springs; substrate normally mucky and fish exist among the plants (Schenck and Whiteside 1976; Burr 1980; Keuhne and Barbour 1983).
Spawning season: Year round, apparently with two spawning peaks, in August and late winter (Schenck and Whiteside 1977b). According to Strawn (1955; 1956), species will spawn readily at temperatures in the low 70’s and high 60’s; spawns year round in San Marcos Springs, Texas, in water ranging 3 – 5 degrees above and below 72 degrees C. Hubbs (1985) documented fertilized eggs 10 months out of the year (none in August and September).
Spawning location: Female lays adhesive eggs on filamentous algae and plants (Strawn 1956).
Reproductive strategy: Provides no parental care of eggs (Strawn 1956).
Fecundity: Bonner et al. (1998) reported mean egg production (± 1 SD) is 760 (±310) per two breeding pairs during a 33-day period at 23 degrees C, under laboratory conditions; optimal temperatures for egg production range from 14-27 degrees C, and 14-25 degrees C for larval production. Schenck and Whiteside (1977b) reported collection of mature ova (mean diameter 1.1 mm) in females 24 mm TL and longer in each month of the year; mean number of mature ova found in 74 females was 19. In aquaria, diameters of eggs ranged from 1.2-1.4; mature, water hardened eggs were heart shaped, slightly indented, vertically compressed, demersal, and adhesive; eggs contained a translucent, pale yellow yolk, a single oil globule (averaging 0.36 mm maximum diameter), smooth chorion, wide perivitelline space, and were unpigmented; eggs incubated at 20 degrees C began hatching on day 4 after fertilization and continued through day 7 (Simon et al. 1995).
Age at maturation: During laboratory spawning, eggs were collected from fish about 6 months old; in the San Marcos River, mature ova collected from individuals about 3.5 months old (Linam et al. 1993). Females longer than 24 mm TL are considered mature (Schenck and Whiteside 1977b).
Food habits: In the San Marcos River and Spring Lake, Texas, diet consists of immature insects and microcrustaceans; the majority of all fish collected during the spring contained dipteran larvae; during the summer, the majority of fish in the San Marcos River contained dipteran larvae, whereas the majority of those in Spring Lake contained copepods and ephemeropteran larvae; in the fall and winter, a majority of fish in the San Marcos River contained ephemeropteran larvae; majority of Spring Lake specimens contained amphipods during the fall, and copepods during winter; species is selective in how and what food items are consumed, with diet varying with relation to the season of year and the size of fish; feeding primarily during the daylight hours (Schenck and Whiteside 1977a). Main food items include cladocerans, copepods, amphipods, and aquatic insects (Bergin et al. 1997).
Growth and population structure: Fish held at approximately 24 degrees C for 146 days grew an average of 0.2 mm/day (Brandt et al. 1993). Males outnumber females 1.4:1 (Schenck and Whiteside 1977b).
Phylogeny and morphologically similar fishes
The cypress darter (Etheostoma proeliare) is the closest ally, and one of the closest relatives of E. fonticola (Burr 1978). E. fonticola and E. proliare are similar, but differ in that the former species has a short lateral line with 0-6 pores, 1 anal spine, and cross-hatching on upper and lower side, while the latter species has a short lateral line with 0-9 pores, 2 anal spines, black or brown dashes along side, and spots on upper and lower side (Page and Burr 1991). Based on information from Simon and Kaskey (1992) regarding eggs, larvae, and early juveniles of selected Texas percids, E. fonticola could only be confused with members of subgenus Oligocephalus (Simon et al. 1995); E. fonticola hatches at the smallest total length, has fewer numbers of preanal myomeres than any other Texas percid, and yolk absorption occurs earlier than in members of Oligocephalus (Simon et al. 1995).
Exotic trematode, Centrocestus formosanus (Mitchell et al. 2000; Cantu 2003; McDonald et al. 2006; McDonald et al. 2007).
Commercial or Environmental Importance
Etheostoma fonticola is threatened by reduction of spring flow, resulting from drought and water withdrawals from the Edwards Aquifer (Bonner and McDonald 2005), and exotic species; in an effort to identify general conservation measures for water quality, and habitat maintenance, a recovery plan for San Marcos and Comal springs and associated ecosystem was revised in 1996 (U.S. Fish and Wildlife 1996; Bonner and McDonald 2005). During periods of low flows, the National Fish Hatchery and Technology Center in San Marcos, Texas, serves as a refugium (Brandt et al.1993; Bonner and McDonald 2005). Restriction on channel modification, streamside development, pollution, and excessive water usage has been recommended for the well-being of the species (Keuhne and Barbour 1983).
[Additional literature noting collection of this species from Texas locations includes, but is not limited to the following: Strawn and Hubbs (1956).]
Bergin, S., T. Arsuffi, B.G. Whiteside, T.M. Brandt, and J.N. Fries. 1995. Food of the fountain darter (Etheostoma fonticola) in the Comal River, New Braunsfels, Texas (August and November 1993). Interim Project Report, February 1995. 21 pp.
Bonner, T.H., and D.L. McDonald. 2005. Threatened fishes of the world: Etheostoma fonticola (Jordan & Gilbert 1886) (Percidae). Environmental Biology of Fishes 73(3):333-334.
Bonner, T.H., T.M. Brandt, J.N. Fries, and B.G. Whiteside. 1998. Effects of temperature on egg production and early life stages of the fountain darter. Transactions of the American Fisheries Society 127:971-978.
Brandt, T.M., K.G. Graves, C.S. Berkhouse, T.P. Simon, and B.G. Whiteside. 1993. Laboratory spawning and rearing of the endangered fountain darter. Progressive Fish-Culturist 55:149-156.
Burr, B.M. 1978. Systematics of the percid fishes of the subgenus Microptera, genus Etheostoma. Bull. Ala. Mus. Nat. Hist. 4:1-53.
Burr, B.M. 1980. Etheostoma fonticola (Jordan and Gilbert), Fountain darter. pp. 648 in D. S. Lee et al., Atlas of North American Freshwater Fishes. N. C. State Mus. Nat. Hist., Raleigh, i-r+854 pp.
Cantu, V. 2003. Spatial and temporal variation of Centrocestus formosanus in river water and endangered fountain darters (Etheostoma fonticola) in the Comal River, TX. M.S. Thesis. Texas State University, San Marcos. 58 pp.
Deacon, J.E., G. Kobetich, J.D. Williams, S. Contreras. 1979. Fishes of North America endangered, threatened, or of special concern: 1979. Fisheries 4(2):29-44.
Hubbs, C. 1985. Darter reproductive seasons. Copeia 1985(1):56-68.
Hubbs, C., R. J. Edwards, and G. P. Garrett. 1991. An annotated checklist of the freshwater fishes of Texas, with keys to identification of species. Texas Journal of Science, Supplement 43(4):1-56.
Jordan, D.A., and C.H.Gilbert. 1886. List of fishes collected in Arkansas, Indian Territory, and Texas, in September 1884, with notes and descriptions. Proc. U.S. Natl. Mus.  9:1-25.
Kuehne, R.A., and R.W. Barbour. 1983. The American Darters. The University Press of Kentucky, Lexington, Kentucky. 177 pp.
Linam, G.W, Mayes, K.B., Saunders, K.S. 1993. Habitat utilization and population size estimate of fountain darters, Etheostoma fonticola, in the Comal River, Texas. Tex. J. Sci 45: 341-348.
McDonald, D.L., T.H. Bonner, E.L. Oborny, Jr., and T.M. Brandt. 2007. Effects of the fluctuating temperatures and gill parasites on reproduction of the fountain darter, Etheostoma fonticola. Journal of Freshwater Ecology 22:311-318.
McDonald, D.L., T.H. Bonner, T.M. Brandt, and G.H. Trevino. 2006. Size susceptibility to trematode-induced mortality in the endangered fountain darter (Etheostoma fonticola). Journal of Freshwater Ecology. 21(2):293-299.
Mitchell, A.J., A.E. Goodwin, M.J. Salmon, D.G. Huffman, and T.M. Brandt. 2000. Prevalence and pathogenicity of a heterophyid trematode infecting the gills of an endangered fish, the fountain darter, in two central Texas spring-fed rivers. Journal of Aquatic Animal Health 12(4):283-289.
Page, L.M. 1983. Handbook of Darters. T.F.H. Publications, Neptune City, NJ. 271 pp.
Page, L.M., and B.M. Burr. 1979. The smallest species of darter (Pisces: Percidae). American Midland Naturalist 101(2):452-453.
Page, L.M., and B.M. Burr. 1991. A Field Guide to Freshwater Fishes of North America, north of Mexico. Houghton Mifflin Company, Boston. 432 pp.
Schneck, J.R., and B.G. Whiteside. 1976. Distribution, habitat preference and population size estimate of Etheostoma fonticola. Copeia 1976(4):697-703.
Schenck, J.R. and B.G. Whiteside. 1977a. Food habits and feeding behavior of the fountain darter, Etheostoma fonticola (Osteichthyes: Percidae). Southwest. Naturalist 21:487-492.
Schenck, J.R. and B.G. Whiteside. 1977b. Reproduction, fecundity, sexual dimorphism and sex ratio of Etheostoma fonticola (Osteichthyes: Percidae). American Midland Naturalist 98:365-375.
Simon, T.P., and J.B. Kaskey. 1992. Description of eggs, larvae, and early juveniles of the bigscale logperch, Percina macrolepida Stevenson, from the West Fork of the Trinity River Basin, Texas. Southwestern Naturalist 37:28-34.
Simon, T.P., T.M. Brandt, K.G. Graves, B.G. Whiteside. 1995. Ontogeny and description of eggs, larvae, and early juveniles of the fountain darter, Etheostoma fonticola. The Southwestern Naturalist 40(2):208-215.
Strawn, K. 1955. A method of breeding and raising three Texas darters, Part I. Aquarium J. 26:408-412.
Strawn, K. 1956. A method of breeding and raising three Texas darters, Part II. Aquarium J. 27:11-14, 17, 31.
Strawn, K., and C. Hubbs. 1956. Observations on stripping small fishes for experimental purposes. Copeia 1956(2):114-116.
U.S. Fish and Wildlife Service. 1996. San Marcos/Comal (Revised) recovery plan. U.S. Fish and Wildlife Service, Albuquerque, New Mexico.
Warren, M.L, Jr., B.M. Burr, S.J. Walsh, H.L. Bart, Jr., R.C. Cashner, D.A. Etnier, B. J. Freeman, B.R. Kuhajda, R.L. Mayden, H.W. Robison, S.T. Ross, and W.C. Starnes. 2000. Diversity, Distribution, and Conservation status of the native freshwater fishes of the southern United States. Fisheries 25(10):7-29.