Lucania parva

rainwater killifish



Type Locality

Beesley's point, New Jersey (Baird and Girard in Baird 1855).


Etymology/Derivation of Scientific Name

Lucania: a coined name without meaning; parva: small (Ross 2001).



Cyprinodon parvas Baird and Girard in Baird 1855:345.

Lucania venusta Evermann 1899:309.

Lucania parva Cook 1959:159.



Maximum size:  62 mm SL (Gunter 1950).


Coloration: Body not barred (Hubbs et al. 1991). Back silvery to light green, with a narrow, dark middorsal stripe. Scales on sides outlined in melanophores, creating cross-hatched pattern, which is especially prominent in breeding males. Forward and upper surfaces of the head speckled with melanophores, which also extend onto the underside of the lower jaw. Belly and undersides of body are silver. Fins generally lack pigmentation, except for some melanophores along the rays. In breeding males, dorsal fin has a black anterior blotch and dark marginal and basal bands that may include orange pigmentation. Caudal, anal, and pelvic fins red to orange, with black marginal bands (Gunter 1950; Simpson and Gunter 1956; Ross 2001).


Counts: 10+ dorsal fin rays; 8-13 scale rows from pelvic origin to isthmus; 30 or fewer longitudinal scale rows (Hubbs et al. 1991); 27 (26-28) lateral scales; 11 (9-13) dorsal fin rays; 13 (12-14) pectoral fin rays; 6 (4-7) pelvic fin rays; 9 (8-13) anal fin rays; 16 (15-18) caudal fin rays; 8 (5-9) gill rakers on 1st arch (Sublette et al. 1990).


Body shape:  Body deep, rather compressed; head flattened above, tapering to vertically rounded, blunt snout (Hardy 1978). Body depth contained four times in standard length (Hubbs et al. 1991). Body axis straight (Sublette et al. 1990).


Mouth position: Supraterminal, oblique; mouth small; obliquely sloped, protruding lower jaw (Sublette et al. 1990).


External morphology: Distance from origin of dorsal fin to end of hypural plate more than distance from origin of dorsal fin to preopercle (Hubbs et al. 1991); dorsal and caudal fins rounded; pectorals, pelvic, anal fins rounded at apex (Sublette et al. 1990). Males develop prickly contact organs on top and sides of head and on side of body between dorsal and anal fin bases (Foster 1967; Collette 1977). Female with membranous sheath surrounding genital opening (Sublette et al. 1990).


Internal morphology: Teeth conical and simple (Hubbs et al. 1991). Premaxillary and mandibular teeth uniserial or irregular, occasionally with a few strong inner teeth (Sublette et al. 1990).


Distribution (Native and Introduced)

U.S. distribution: Native to coastal waters from Massachusetts to Tampico, Mexico (Hubbs et al. 1991). Introduced into California, Nevada, Oregon, and Utah (Hubbs and Miller 1965). Locally abundant in lower Pecos River drainage, New Mexico, not ascending tributary streams far above mouth (Cowley and Sublette 1987).


Texas distribution: Occurs in the Pecos River, Leon Creek, and in Falcon Reservoir in the Rio Grande Basin; recently introduced (ca. 1980) into Clear Creek (Menard County, San Saba River Drainage; Hubbs et al. 1991). Warren et al. (2000) list the following drainage units for distribution of Lucania parva in the state: Sabine Lake (including minor coastal drainages west to Galveston Bay), Galveston Bay (including minor coastal drainages west to mouth of Brazos River), Brazos River, Colorado River, San Antonio Bay (including minor coastal drainages west of mouth of Colorado River to mouth of Nueces River), Nueces River. Hubbs (1957) suggested that the species may occupy most of the Tamaulipan Biotic Province.


Abundance/Conservation status (Federal, State, NGO)

Populations in southern United States are currently stable (Warren et al. 2000). Usually abundant in preferred habitat (Duggins 1980a).


Habitat Associations

Macrohabitat: Found in salt marshes, bays, and lagoons from Cape Cod, Massachusetts to Tampico, Mexico (Duggins 1980a); common in freshwaters of St. John’s River system, Florida (Burgess 1977), and Rio Grande and Pecos River in Texas and New Mexico (Duggins 1980a). Lucania parva is a schooling species (Hardy 1978).


Mesohabitat: Tolerates wide range of salinity; invariably collected in presence of aquatic vegetation (Duggins 1980a). Rhodes and Hubbs (1992) reported that species was more abundant at all saline sample sites than at any of the freshwater sampling sites on the Pecos River, Texas. Species seems to inhabit primarily brackish water with salinities of 0.7-24.2 ppt throughout most of range (Gunter 1950; Miller and Guillory 1980). Gunter (1950) reported species avoidance of salt flats and bay shores, and preference for fresher waters in ponds and sloughs of the Aransas Refuge, on the south Texas coast. In Mississippi, species found in vegetated areas along lower, tidally influenced sections of coastal rivers; in Old Fort Bayou, near Ocean Springs, species was most common at sites with an average salinity of 4 ppt, and less common at sites with either higher or lower values (Peterson and Ross 1991). In the St. Johns River estuary, Florida, Jordan (2002) found Lucania parva almost exclusively in structurally complex beds of tapegrass (Vallisneria Americana); observations of fish, in the laboratory, indicated species preference for vegetated over unvegetated habitats in the absence of both potential prey and predators, and a further increased utilization of vegetated habitats when predatory largemouth bass (Micropterus salmoides) were added.



Spawning season: In Texas, females began ripening in February, and a few were gravid in July; peak spawning in May and June (males displayed breeding coloration from February into June, or July, with greatest color intensity in May; Gunter 1950); may occur in earlier in the spring (Simpson and Gunter 1956). Sublette et al. (1990) reports spawning in New Mexico from spring – fall, at least in southern portion of state.


Spawning location: During spawning, male and female swim into vegetation with fine leaves; there eggs are released and fertilized; eggs have mucous threads with which they are attached to plant material (Foster 1967). McLane (1955) noted that male courtship behavior was observed near clumps of Naias and Vallisneria.


Reproductive strategy: A courting male swims in loops slightly below the female, waiting for the female to respond by stopping; after a female stops, the male moves under her flicking his head against her throat; pair moves slowly toward surface of the water, while male continues to rub his head against underside of the female; when they are near surface, female swims into vegetation having fine leaves or algal masses, and the male follows; using his dorsal and anal fins, the male then clasps female, and eggs are released and fertilized (Foster 1967).


Fecundity: 7-46 ripe ova (mean 24.5 per fish) plus numerous smaller ova (McLane 1955); maximum reported count 104 (Hildebrand and Schroeder 1928; Hardy 1978). Freshly laid eggs are spherical, nearly colorless, having chorionic threads; live eggs averaging 1.23 mm in diameter; eggs hatch in 6 days at water temperature of 23.9 degrees C (Foster 1967). More than one brood may be produced per year by a single female (Hardy 1978).


Age/Size at maturation:  3-5 months after hatching, at a minimum size of 25 mm TL (Hildebrand and Schroeder 1928).


Migration:  Mass downriver migration of thousands of fish was noted in York River Virginia, in mid-October, and inshore in Florida Keys only during October, November and February (Hardy 1978). Species may be anadromous, moving into lower salinity water for breeding, and returning to higher salinity water after breeding (Foster 1967).




Food habits:  After hatching and spending about one week on the bottom until yolk sac is absorbed, young fish move up into water column and begin to feed (Foster 1967). Simpson and Gunter (1956) and Harrington and Harrington (1961) reported diet items including larval crustaceans (mainly cyclopoid and harpacticoid copepods), mosquito larvae, small worms, and mollusks. Harrington and Harrington (1961) noted that the species heavily predates both larvae and pupae of saltmarsh mosquitoes.


Growth and Population structure: Females larger than males (Hardy 1978); average difference in size is about 6 mm (Hildebrand and Schroeder 1928). In Texas, Gunter (1950) collected most fish in May, June, and July, with total length-frequency curves indicating two groups, from 18-33 mm, and 43-53 mm in length; many fish around 18 mm in length were collected in April and May, but the majority of this group had disappeared through growth, and most of the larger group was no longer present in July; crude mode during most months was 23 mm in length, although in April and May most fish were from 17-25 mm long, and the majority were from 21-30 mm long in June and July.


Phylogeny and morphologically similar fishes

Species shows considerable variation (usually clinal) throughout range, but division into subspecies probably not justified (Duggins 1980a); species displays no geographic differences in morphology or isoenzymes (Duggins 1980b).  Based on morphological characters of Lucania parva from the Pecos River, Hubbs and Miller (1965) suggest that the population may be representative of a distinct race. Lucania parva superficially similar to mosquitofishes, from which it differs in lacking the modified anal fin in males (gonopodium) and in having the third anal ray branched in female; also, dorsal origin in advance of the anal fin origin in rainwater killifishes (Ross 2001).  Lack of barring will distinguish L. parva from the other killifishes; position of the dorsal, inserted before, instead of behind the front of the anal fin, will distinguish L. parva from the livebearers (Koster 1957).


Host Record

Trematoda: Parascocotyle diminuta (Hoffman 1967); trematode worms, Gyrodactylus (Tyler 1963).


Commercial or Environmental Importance

In an effort to escape predators, such as bluegills (Lepomis macrochirus), fish may jump from the water onto surface of a lily pad when pursued, lying motionless for up to ten seconds before reentering the water; however, the predator may sometimes take the fish by biting through the lily pad (Baylis 1982). Able (1976) noted that Lucania parva will remove external parasites from other members of its species, and from the sheepshead minnow (Cyprinodon variegatus); a fish having parasites will swim almost vertically, with its head up, to let other fishes know that it is receptive to being cleaned ; Tyler (1963) observed similar cleaning behavior involving L. parva specimens collected from a weed bed near Solomons, Maryland, on Chesapeake Bay, which were externally parasitized by trematode worms, Gyrodactylus.


[Additional literature noting collection of this species from Texas locations includes, but is not limited to the following: Hubbs (1954); lower Rio Grande (Robinson 1959); Cow Bayou (Linam and Kleinsasser 1987a); Hillebrandt Bayou (Linam and Kleinsasser 1987b); Gelwick et al. (2001); lower Rio Grande (Edwards and Contreras-Balderas 1991); Independence Creek (Bonner et al. 2005).]



Able, K. W. 1976. Cleaning behavior in the cyprinodontid fishes: Fundulus majalis, Cyprinodon variegatus, and Lucania parva. Chesapeake Sci. 17(1):35-39

Baird, S.F. 1855. Report on the fishes observed on the coasts of New Jersey and Long Island during the summer of 1854, pp. 317-353. In: Ninth annual report of the Smithsonian Institution (1854). Smithsonian Institution, Washington D.C.

Baylis, J.R. 1982. Unusual escape response by two cyprinodontiform fishes, and a bluegill predator's counter-strategy. Copeia 1982(2):455-457.

Bonner, T.H., C.Thomas, C.S. Williams, and J.P. Karges. 2005. Temporal assessment of a west Texas stream fish assemblage. The Southwestern Naturalist 50(1):74-106.

Collette, B.B. 1977. Epidermal breeding tubercles and bony contact organs in fishes. Symp. Zool. Soc. Lond. 39:225-268.

Cook, F.A. 1959. Freshwater fishes in Mississippi. Mississippi Game and Fish Commission, Jackson. 239 pp.

Cowley, D.E., and J.E. Sublette. 1987. Distribution of fishes in the Black River drainage, Eddy County, New Mexico. Southwestern Naturalist 32(2):213-221.

Duggins, C.F., Jr. 1980a. Lucania parva (Baird), rainwater killifish, p. 535. In: D. S. Lee, et al.  Atlas of North American Fishes.  N. C. State Mus. Nat. Hist., Raleigh, i-r+854 pp.

Duggins, C.F., Jr. 1980b. Systematics and zoogeography of Lucania parva, Floridichthys, and Menidia (Osteichthyes: Atheriniformes) in Florida, the Gulf of Mexico and Yacatan. Dis Abst. Int. 41B(3):849-850.

Edwards, R.J., and S. Contreras-Balderas. 1991. Historical changes in the ichthyofauna of the lower Rio Grande (Rio Bravo del Norte), Texas and Mexico. The Southwestern Naturalist 36(2):201-212.

Evermann, B.W. 1899. Report on investigations by the U.S. Fish Commission in Mississippi, Louisiana, and Texas, in 1897. Rept. U.S. Fish Comm. 24:287-310.

Foster, N.R. 1967. Comparative studies on the biology of killifishes (Pisces: Cyprinodontidae). Ph.D. diss. Cornell Univ., Ithaca, N.Y. 391 pp.

Gelwick, F.P., S.Akin, D.A. Arrington, and K.O. Winemiller. 2001. Fish assemblage structure in relation to environmental variation in a Texas Gulf Coastal wetland. Estuaries 24(2):285-296.

Gunter, G. 1950. Distributions and abundance of fishes on the Aransas National Wildlife Refuge, with life history notes. Publ. Inst. Mar. Sci., Univ. Tex. 1(2):89-101.

Hardy, J.D., Jr. 1978. Development of Fishes of the Mid-Atlantic Bight: an atlas of egg, larval and juvenile stages. Volume 2: Anguillidae through Syngnathidae. U.S. Fish and Wildlife Service Biological Services Program, Solomons, Maryland. 458 pp.

Harrington, R.W., Jr., and E.S. Harrington. 1961. Food selection among fishes invading a high subtropical salt marsh; from onset of flooding through the progress of a mosquito brood. Ecology 42(4):646-666.

Hildebrand, S.F., and W.S. Schroeder. 1928. Fishes of Chesapeake Bay. Bulletin of the U.S. Bureau of Fisheries 43(1):1-336.

Hoffman, G.L. 1967. Parasites of North American Freshwater Fishes. University of California Press, Berkeley. 486 pp.

Hubbs, C. 1954. Corrected distributional records for Texas fresh-water. Texas Journal of Science 1954(3):277-291.

Hubbs, C. 1957. Distributional patterns of Texas fresh-water fishes. The Southwestern Naturalist 2(2/3):89-104.

Hubbs,C., and R.R. Miller. 1965. Studies of cyprinodont fishes. XXII. Variation in Lucania parva, its establishment in western United States, and description of a new species from Interior Basin in Coahuila, Mexico. Misc. Publ. Mus. Zool., Univ. Mich. No.127:1-104.

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, F. 2002. Field and laboratory evaluation of habitat use by rainwater killifish (Lucania parva) in the St. John’s River estuary, Florida. Estuaries 25(2):288-295.

Linam, G.W., and L.J. Kleinsasser. 1987a. Fisheries attainability study for Cow Bayou (Segment 0511). River Studies Report No. 5. Resource Protection Division. Texas Parks and Wildlife Department, Austin. 14 pp.

Linam, G.W., and L.J. Kleinsasser. 1987b. Fisheries attainability study for Hillebrandt Bayou. River Studies Report No. 1. Resource Protection Division. Texas Parks and Wildlife Department, Austin. 18 pp.

McLane, W.M. 1955. Fishes of the St. Johns River System. Ph.D. dissertation. University of Florida, Gainsville. 361 pp.

Miller, C. and V. Guillory. 1980. A comparison of marsh fish communities using the Wegener ring. Proc. S.E. Assoc. Fish Wildl. Agencies 34:223-233.

Peterson, M.S. and S.T. Ross. 1991. Dynamics of littoral fishes and decapods along a coastal river-estuarine gradient. Estuarine, Coastal and Shelf Sci. 33:467-483.

Rhodes, K., and C. Hubbs. 1992. Recovery of Pecos River fishes from a red tide fish kill. The Southwestern Naturalist 37(2):178-187.

Robinson, D.T. 1959. The ichthyofauna of the lower Rio Grande, Texas and Mexico. Copeia 1959(3):253-256.

Ross, S.T. 2001. The Inland Fishes of Mississippi. University Press of Mississippi, Jackson. 624 pp.

Simpson D.G., and G. Gunter. 1956. Notes on habitats, systematic characters and life histories of Texas saltwater cyprinodontes. Tulane Stud. Zool. 4(4):115-134.

Sublette, J.E., M.D. Hatch, and M. Sublette. 1990. The Fishes of New Mexico. University of New Mexico Press, Albuquerque. 393 pp.

Tyler, A.V. 1963. Cleaning symbiosis between the stickleback and rainwater fish. Underwater Naturalist 1(4):18-19.

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.