Did You Know? 17 Incredible Rainwater Killifish Facts

Rainwater killifish facts, belongs to Fundulidae family is widely found in St. John's River Estuary, Florida Estuaries, the Rio Grande, able to tolerate a wide range of salinities.

Do you love fishkeeping or like to have your aquarium filled with colorful fishes? Then we are sure killifish is a good and best option you should go for. So here we are, taking you on the descriptive journey of such amazingly beautiful and exotic rainwater killifish (Lucania parva).

Rainwater killifish, type locality: Beesley's Point, New Jersey (Baird and Girard in Baird 1855) is a calm fish that can tolerate a different range of environmental conditions, complexity, and salinity. This miniature fish resembles a tiny and brilliantly sparkling diamond that swims through a wide range of river systems. These are the best options for rearing, as they help control algae and mosquito larvae. An interesting feature is this fish loves jumping, so the aquarist should be careful while handling this fish, or else you may find your fish on the floor. This deep-bodied fishs' scientific name is Lucania Parva, Lucania is a coined name with no meaning, and Parva is referred to as small. The rainwater killifish is one of the smallest fish in Alabama. This killifish is a native of North America, New Mexico, and the Texas river system.

To know about such similar species, check out codfish facts or fluke fish facts.

Rainwater Killifish

Fact File

What do they prey on?

Larval Crustaceans, Mosquito Larvae, Small Worms

What do they eat?


Average litter size?


How much do they weigh?


How long are they?

1 - 3 in (25.4 - 76.2 mm)

How tall are they?


What do they look like?

Silver, Olive Green

Skin Type

Moist Scales

What are their main threats?

Herons, Egrets, Striped Bass, Bluefish

What is their conservation status?

Least Concern

Where you'll find them

Freshwaters, Shallow Waters, Salt Marshes, Bays, Lagoons


Florida, Massachusetts, Tampico, Texas, New Mexico





Scientific Name

Lucania parva





Rainwater Killifish Interesting Facts

What type of animal is a rainwater killifish?

The rainwater killifish (Lucania parva) is a scintillating silvery-colored fish with a straight body axis. It is one of the freshwater fishes with up to 13 dorsal-fin rays, up to 13 anal fin rays and depends on mosquito larvae.

What class of animal does a rainwater killifish belong to?

Rainwater killifish belongs to the class Actinopterygii and the family Fundulidae. Rainwater killifish scientific name Lucania Parva. Most species of this family are small fishes less than 3.9 in (9.9 cm) in length. Rainwater killifish is a topminnow family fish; the fishes which belong to this family have a small body with large eyes, flattened head and back, one dorsal fin far back on the body, and an upturned mouth.

How many rainwater killifish are there in the world?

The total population of these rainwater killifish( L.parva) is unknown, but its population is stable as per IUCN. As per T. Bonner, Texas State University, the population of L. Parva fish is rare in the habitat of San Francisco Bay and abundant in some parts of the Texas Pecos River. A considerable amount of these killifish was taken out of the Pecos River system (Texas) at 89.6°F (32°C) water temperature.

Where does a rainwater killifish live?

This killifish is a habitat generalist. These species range from Cape Cod, Massachusetts, to Tampico, Mexico. Rainwater killifish are located commonly in estuarine waters along the Atlantic and Gulf of North America, Florida, waters of the Rio Grande and Pecos River in Texas, and New Mexico. These species are common in St. John's River Estuary, Florida Estuaries, which are located in Florida. In addition, this killifish introduced in Utah, Nevada, Oregon, Oregon, and California (Hubbs and Miller 1965).

What is a rainwater killifish's habitat?

Rainwater killifish Lucania Parva is commonly found in estuarine waters, freshwater rivers, salt marshes, bays (Cape Cod, Massachusetts). Its population was also introduced west of the Rocky Mountains through the stocking oysters and freshwater sport fishes.

This fish is anadromous species. The species L. Parva migrates to more saline waters during the nonbreeding season and waters with a lower saline level during the breeding season in the USA.

Who does rainwater killifish live with?

Rainwater killifish (L. Parva) is a small fish that lives in schools in estuarine waters. Though not known much about these freshwater fishes, killifishes exist in small streams, where male species head the group.

In an aquarium environment, the male species are aggressive towards each other, and aggression can be avoided by not placing any other male species in the tank.

How long does a rainwater killifish live?

The exact lifespan of these brackish water species is not known; it is likely in between one and two years. In captivity, the life span of this fish may differ from that in the wild.

How do they reproduce?

Rainwater killifish reproduce through sexual reproduction. During courtship, the male starts swimming in loops around the female, waiting for its response. When the female stops, both pairs move slowly under the water surface; during this stage, the male continuously flicks his head against the female species throat. Under the surface, mating occurs where the male clasps the female with the help of the dorsal fin and anal fins.

After this beautiful romantic moment, the female releases the ova and is fertilized further. The female releases up to 46 ripe ova, and the number of minor ova total count is 104. The freshly laid eggs have mucous threads that help attach to the plant material. The eggs are spherical with no color, with an average diameter of 0.04 in (1.23 mm).

Within six days at 75.02°F (23.9°C) temperature, the eggs hatch, and they become mature within five months. Thus, a single female produces more than one brood per year.

The breeding season is between February and July, while the breeding peaks during May and June. In New Mexico, the spawning is between spring through autumn. The breeding starts in early February and ranges till July in Texas.

What is their conservation status?

As per IUCN, the conservation status of this rainwater killifish, Lucania Parva, is of Least Concern. Because of their outstanding talent to handle a wide range of pollutants (pesticides and fertilizers), salinities, and temperatures, this brackish water killifish is one of the least concerned species.

Rainwater Killifish Fun Facts

What do rainwater killifish look like?

Lucania Parva, Baird, and Girard first introduced this killifish.

The rainwater killifish is one of the small freshwater fishes of texas in silvery to olive green pigmentation. Belly and rainwater killifish body shape is compressed and had a small obliquely shaped mouth, protruding lower jaw. The breeding male has a dorsal fin with black anterior blotch, in dusky orange to yellow pigmentation. Caudal, anal, and pelvic fins are in red to orange color with black marginal bands. Dorsal and caudal fins are rounded, whereas pectoral, pelvic and anal fins are rounded at the apex. Their teeth are conical and simple in shape.

How cute are they?

This estuarine and small, peaceful fluorescent-colored fish are as cute as a button. Any aquarist cannot resist complementing the beauty of diamond-shaped scales of the rainwater killifish (Lucania Parva).

How do they communicate?

In general, fishes communicate by gestures, motions, and sometimes with the help of fins. During mating season, the rainwater killifish male seduces female with physical displays such as swimming in loops around the female. The dorsal fin and anal fin play an active role while communicating.

How big is a rainwater killifish?

The average length of these fish is 1 - 3 in (25.4-76.2 mm). Thus, it is comparatively bigger than Heterandria Formosa, whose maximum length is 1.2 in (3 cm).

How fast can a rainwater killifish run?

The exact information regarding the speed of the rainwater killifish is not known. But they can swim several inches down the surface of the water.

How much does a rainwater killifish weigh?

The information regarding the weight of this species is not known, but they are very light weighted killifish abundant in New Mexico.

What are the male and female names of the species?

There are no distinguished names for male and female species. Males are named as male rainwater killifish and female as female rainwater killifish. Simple, right? But the female species are less bright species than the male rainwater killifishes; breeding males have small cross-hatched pattern scales. Male develops the contact organs on both the head and body between the dorsal fin and anal fin bases. At the same time, the female has a membranous sheath surrounding the genital opening.

What would you call a baby rainwater killifish?

Rainwater killifish young species may be named larva, fry, or fingerling based on their stage of development.

What do they eat?

This killifish is a pelagic and surface feeder, primarily inhabit brackish water, and is commonly found in St. John's River Estuary, Florida Estuaries. They feed on mosquito larvae, small worms, mollusks like oysters, and larval crustaceans. Harrington and Harrington (1961) mentioned that they widely depend on larvae and pupae of saltmarsh mosquitoes.

Are they poisonous?

The dorsal fin rainwater killifish (L. parva) is not poisonous species and is harmless to humans. These freshwater species can survive in a wide range of salinities and extremely pollutant water bodies.

Would they make a good pet?

Yes, these beautifully colored dorsal finfish species are easily adaptable and will be good pets. They are convenient and easily adjust to the different types of habitat and water conditions such as brackish water and rainwater.

Did you know...

When referring to its life history, Baird and Girard (1855) provided the first description of these species with scientific names as Cyprinodon Parvus. Later this species was added to the genus Lucania; this rainwater killifish scientific name was changed to Lucania Parva in 1883.

Juveniles are sometimes confused with some mosquitofish species belonging to the topminnow family.

Do you know some killifish species can survive out of the water for up to 66 days?

Do humans eat them?

No, they are just small fish; we humans do not prefer to eat the killifishes. But they help control the spread of malaria as they feed as mosquito larvae.

Do they bite?

No relevant information on rainwater killifish (Lucania parva) bites is available, but in general, the killifishes are calm and peaceful creatures. Usually, some species of male killifishes are aggressive and may harm the other male species, so better care should be taken by the aquarists who are thinking of adopting these killifishes.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other fish from our swai fish facts and skate fish facts pages.

You can even occupy yourself at home by coloring in one of our free printable rainwater killifish coloring pages.



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