The rainwater killifish (Lucania parva) is a small silvery fish with yellow flashes and diamond shaped scales that is widespread from Cape Cod, Massachusetts, through to Tampico, Mexico.

It is commonly found in large numbers in fresh to brackish estuarine environments.

It feeds on tiny crustaceans, mosquito larvae, small worms, and mollusks.

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.

In breeding males, dorsal fin has a black anterior blotch and dark marginal and basal bands that may include orange pigmentation.

Body depth contained four times in standard length (Hubbs et al. 1991).

Female with membranous sheath surrounding genital opening (Sublette et al. 1990).

Internal morphology: Teeth conical and simple (Hubbs et al. 1991).

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.

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).

Spawning season: In Texas, females began ripening in February, and a few were gravid in July.

Peak spawning is 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 the southern portion of the state.

McLane (1955) noted that male courtship behavior was observed near clumps of Naias and Vallisneria.

The pair moves slowly toward the surface of the water, while the male continues to rub his head against the underside of the female.

When they are near the surface, the female swims into vegetation having fine leaves or algal masses and the male follows.

Using his dorsal and anal fins, the male then clasps the female, and eggs are released and fertilized (Foster 1967).

The rainwater killifish is native to coastal waters from Massachusetts to Tampico, Mexico (Hubbs et al. 1991).

It has been introduced into California, Nevada, Oregon, and Utah (Hubbs and Miller 1965).

It is locally abundant in lower Pecos River drainage, New Mexico, not ascending tributary streams far above mouth (Cowley and Sublette 1987).

The rainwater killifish was formally described by Spencer Fullerton Baird and Charles Frédéric Girard as Cyprinodon parvus with the type locality given as Beesley's Point, New Jersey and as Greenport, Long Island, New York.

Southwestern Naturalist 32(2):213-221. et al. Atlas of North American Fishes.

Menidia (Osteichthyes: Atheriniformes) in Florida, the Gulf of Mexico and Yacatan.

in relation to environmental variation in a Texas Gulf Coastal wetland.

high subtropical salt marsh; from onset of flooding through the progress of a mosquito brood.

Naturalist 2(2/3):89-104. parva, its establishment in western United States, and description of a new species from Interior Basin in Coahuila, Mexico.

Diversity, Distribution, and Conservation status of the native freshwater fishes of the southern United States.