Rio Seco near Ft. Inge, Texas (Girard 1860).
Etymology/Derivation of Scientific Name
Etheostoma, from the Greek, etheo, “to strain,” and stoma, “mouth;” gracile, Latin, meaning “slender” or “thin” (Pflieger 1997).
Beleosoma gracile Girard 1860:103.
Peocilichthys butlerianus Hay 1883:61.
Etheostoma gracile Cook 1959:207.
Maximum size: 50 mm SL (Page 1983).
Life colors: Yellow above, green saddles and wavy lines on back; bright green bars on side of male, green squares or mottling on female; yellow to white below; blue-gray edge and base, middle red band on 1st dorsal fin (faint on female); thin teardrop (Page and Burr 1991).
Counts: 44-52 (40-55) lateral line scales; 7-13 (9-10) dorsal spines; 11-12 (9-14) dorsal rays; 2 anal spines; 6-7 (5-8) anal rays, and 13 (12-14) pectoral rays (Page 1983).
Body shape: Elongate, shallow (Ross 2001). Head profile rounded, profile in front of eye less than 45 degrees; snout less conical, not extending beyond upper lip. Body depth contained in standard length less than seven times (Hubbs et al. 1991).
Mouth position: Terminal, oblique (Ross 2001).
External morphology: Infraorbital canal uninterrupted, six to eight (usually eight pores); breast unscaled; distance from snout to angle of gill cover equal to one-half of head length; lateral line with a slight upward curve anteriorly; pectoral fin shorter than head, not reaching anus; belly scaled (a narrow naked band may be present on midline); preopercle smooth or less serrate; upper jaw not extending as far as to below middle of eye (Hubbs et al 1991). Second anal spine is very thin and easily overlooked. Female genital papilla is a moderately elongate tube with a blunt end. Males develop large breeding tubercles on the lower part of the anal fin rays, the pelvic fin, and lower jaw (Ross 2001, Collette 1962).
Distribution (Native and Introduced)
U.S. distribution: Streams throughout the Gulf Coastal Plain (Hubbs et al. 1991).
Texas distribution: From the Rio Grande to the Red River; most records for species end at the Nueces River (Hubbs et al. 1991).
Abundance/Conservation status (Federal, State, NGO)
Populations in the southern United States are currently secure (Warren 2000).
Macrohabitat: Found in ditches, swamps, quiet backwaters, and slow to moderately flowing areas of low-gradient streams (Collette 1962; Braasch and Smith 1967).
Mesohabitat: Over mud or silt substrata (Collette 1962; Braasch and Smith 1967). In Texas, 64% of collections of this species were in areas with zero to moderate current speeds, and the majority of sites either lacked vegetation or had only slight to moderate amounts (Collette 1962).
Spawning season: In Texas, late January-March in Texas (Hubbs 1985); maximum spawning in mid-March (Collete 1962). In Illinois, late May or early June (Braasch and Smith 1967).
Spawning location: Phytophils; have adhesive eggs that are attached to a variety of plants. Free embryos without cement glands swim instantly after a prolonged embryonic period (Simon 1999).
Reproductive strategy: Males acquire breeding tubercles which presumably assist in maintaining contact with the female during spawning. During courtship, male chases the female and places himself above or alongside female, oriented head to head. Once above her, the male vibrates his pectoral fins and rubs chin tubercles over her head and snout. After successful courtship, female swims to a suitable site, such as a small twig or leaf, and attaches a single egg. The male then swims over the egg and fertilizes it. The process may be repeated numerous times as the female swims in a circle and then returns to deposit another egg on the object, resulting in precise arrangement of the eggs (Braasch and Smith 1967).
Fecundity: A single female can produce over 2,500 eggs in one season; eggs range from 0.85 – 1.00 mm diameter and have single yellow oil globule; hatching occurs in 5 days at water temperature of 22.8 degrees C (Braasch and Smith 1967).
Age at maturation: Within a year of hatching (Collette 1962).
Longevity: To 4 years (Braasch and Smith 1967).
Food habits: Invertivore; benthic; diet includes primarily midge (dipteran) larvae, mayfly (ephemeroptera) nymphs, and microcrustaceans (copepods and cladocerans; Goldstein and Simon 1999). During winter, major food sources are chironomids, copepods, and cladocerans; mayflies (ephemeroptera) becoming significant in spring (Hocutt and Stauffer 1980). Juveniles may consume very large prey, as one 18 mm SL fish was noted to have consumed a16 mm midge larvae (Braasch and Smith 1967).
Growth: Larvae grow very rapidly, with approximately 50% of average first year growth achieved in first week following hatching. Protolarvae average 2.8 mm TL upon hatching (Braasch and Smith 1967).
Phylogeny and morphologically similar fishes
Etheostoma gracile was placed in the subgenus Hololepis by Collette (1962) and Bailey and Etnier (1988). Page (1981) collapsed the subgenera Hololepis and Microperca into the subgenus Boleichthys. Page (1976) documented an intergeneric hybrid with P. maculata. E. gracile may be confused with E. fusiforme, the swamp darter, and E. proliare, the cypress darter, but it differs from these two in having a complete (vs. incomplete) infraorbital canal with 8 pores rather than 4-6 pores (Ross 2001). E. chlorosomum, the bluntnose darter, and E. gracile are often collected together (Cross and Moore 1952; Collette 1962; Page 1983).
Trematoda, in Texas (Mayberry et al. 2001).
Commercial or Environmental Importance
Bailey, R. M., and D. A. Etnier. 1988. Comments on the subgenera of darters (Percidae) with descriptions of two new species of Etheostoma (Ulocentra) from the southeastern United States. Misc. Publ. Mus. Zool. Univ. Mich. 175:1-48.
Braasch M. E., and P. W. Smith. 1967. The life history of the slough darter, Etheostoma gracile (Pisces: Percidae). III Nat. Hist. Surv. Biol. Notes 58:1-12.
Collette, B. B. 1962. The swamp darters of the subgenus Hololepis (Pisces: Percidae). Tulane Studies of Zoology 9(4):115-211.
Cook, F. A. 1959. Freshwater fishes in Mississippi. Mississippi Game and Fish Commission, Jackson. 239 pp.
Girard, 1860. Ichthyological notes. Proc. Acad. Nat. Sci. Phil. 11:56-68.
Goldstein, R.M., and T.P. Simon. 1999. Toward a united definition of guild structure for feeding ecology of North American freshwater fishes. pp. 123-202 in T.P. Simon, editor. Assessing the sustainability and biological integrity of water resources using fish communities. CRC Press, Boca Raton, Florida.
Hay, O. P. 1883. On a collection of fishes from lower Mississippi valley. Proc. Bull. U.S. Fish Comm. 2:57-75.
Hocutt, C. H., and J. R. Stauffer. 1980. Etheostoma gracile (Girard), Slough darter. pp. 651 in D. S. Lee, et al. Atlas of the North American Freshwater Fishes. N. C. State Mus. Nat. Hist., Raleigh, i-r+854 pp.
Hubbs, C. 1985. Darter reproductive seasons. Copeia. 1985: 56-68
Hubbs, C., R. J. Edwards, and G. P. Garrett. 1991. An annotated checklist of the freshwater fish of Texas, with keys to identification of species. The Texas Journal of Science, Supplement, 43(4):1-56.
Mayberry, L. F., A. G. Canaris, and J. R. Bristol. 2000. Bibliography of parasites and vertebrate host in Arizona, New Mexico, and Texas (1893-1984). University of Nebraska Harold W. Manter Laboratory of Parasitology Web Server pp. 1-100.
Page, L. M. 1976. Natural darter hybrids: Etheostoma gracile x Percina maculata, Percina caprodes x Percina maculata, and Percina phoxocephala x Percina maculata. Southwest. Nat. 21(2):145-149.
Page, L. M. 1981. The genera and subgenera of darters (Percidae: Etheostomatini). Occ. Pap. Mus. Nat. Hist. Univ. Kansas 90:1-69.
Page, L.M. 1983. Handbook of Darters. T.F.H. Publications, Neptune City, NJ. 271 pp.
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.
Pflieger, W. L. 1997. The Fishes of Missouri. Missouri Department of Conservation, Jefferson City, 372 pp.
Ross, S. T. 2001. The Inland Fishes of Mississippi. University Press of Mississippi, Jackson. 624 pp.
Simon, T. P. 1999. Assessment of Balon’s reproductive guilds with application to Midwestern North American Freshwater Fishes, pp. 97-121. In: Simon, T.L. (ed.). Assessing the sustainability and biological integrity of water resources using fish communities. CRC Press. Boca Raton, Florida. 671 pp.
Warren, L. W., 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.