Species: Gambusia affinis

Western Mosquitofish

Species

Fishes

Encyclopedia of Puget Sound

Classification

Kingdom

Animalia

Phylum

Craniata

Class

Actinopterygii

Order

Cyprinodontiformes

Family

Poeciliidae

Genus

Gambusia

NatureServe

Source:
ELEMENT_GLOBAL.2.103578

Classification

Informal Taxonomy

Animals, Vertebrates - Fishes - Bony Fishes - Other Bony Fishes

Formal Taxonomy

Animalia - Craniata - Actinopterygii - Cyprinodontiformes - Poeciliidae - Gambusia - .

Ecology and Life History

Habitat Type Description

Freshwater

Migration

true - false - false

Non-migrant

true

Locally Migrant

false

Food Comments

Opportunistic omnivore; eats mainly small invertebrates, often taken near water surface. Also eats small fishes and, in the absence of abundant animal food, algae and diatoms (Moyle 1976). Mosquitofish are principally carnivorous, and have strong, conical teeth and short guts (Meffe et al. 1983, Turner and Snelson 1984). They are reported to feed on rotifers, snails, spiders, insect larvae, crustaceans, algae, and fish fry, including their own progeny (Barnickol 1941, Minckley 1973, Meffe and Crump 1987). Cannibalism has been documented by several authors (Seale 1917, Krumholz 1948, Walters and Legner 1980, Harrington and Harrington 1982). Plant material is taken occasionally (Barnickol 1941) and may make up a significant portion of the diet during periods of scarcity of animal prey (Harrington and Harrington 1982). Grubb (1972) showed that anuran eggs from temporary ponds were preferentially selected over those breeding in permanent systems. Several workers have documented changes in the prey community after mosquitofish introduction (Hurlbert et al. 1972, Farley and Younce 1977, Hurlbert and Mulla 1981, Walters and Legner 1980). Due to their name, these fishes are popularly believed to be "super" mosquito-larvae predators. Reddy and Shakuntala (1979), however, found that adult females grew poorly on a diet of mosquito larvae, but they grew quickly on tubifex worms. These results matched the outcome of preference tests, i.e. worms were chosen over mosquito larvae. Cech et al. (1980) found that juveniles grew more quickly when they were raised on brine shrimp nauplii than tubifex worms. Many biologists have concluded these fishes are no more effective in mosquito-larval control than various native fishes (Cross 1967). The effectiveness of predation on mosquito larvae decreases as water volume decreases (Reddy and Pandian 1973).

Reproduction Comments

Fish born early in the spring may reproduce later in the summer and fall. Those born late in the reproductive season overwinter before reproducing (Krumholz 1948). In southcentral Texas, young may be collected from March to October with a peak in abundance in April (Davis 1978). In some constant temperature springs, these fish cease reproduction in winter (Brown and Fox 1966, Davis 1978). However, some populations from thermal habitats (such as cooling ponds and lakes) reproduce year-round (Ferens and Murphy 1974, Bennett and Goodyear 1978). At the Savannah River Power Plant site, South Carolina, fish reproduce throughout the winter although at much reduced brood sizes (Meffe, pers. comm., cited in Constantz 1989). These same workers found that the percentage of reproductively active females increased with increasing water temperature. Mosquitofish have internal fertilization and are ovoviviparous (Sublette et al. 1990). Females can store sperm from one copulation and fertilize several broods sequentially (Krumholz 1948). After a gestational period of 21 to 28 days, the young are born alive at a size of approximately eight to nine mm total length (Krumholz 1948). Larger females produce more offspring (Krumholz 1948). Brood sizes of one to 315 young have been reported (Barney and Anson 1921, Moyle 1976). Females annually have four to five broods (Krumholz 1948). Sex ratios are 1:1 at birth, but in older cohorts, the number of males declines relative to the number of females (Krumholz 1948). Under optimal conditions females can become gravid at 6 weeks of age, produce 2-3 broods in first summer. Few individuals live more than 15 months (Moyle 1976). Life history is flexible, varies with environmental conditions (Stearns 1983).

Ecology Comments

May experience severe winter mortality in some areas, but may quickly reestablish population. Predators include water snakes (Nerodia) (Mushinsky and Hebrard 1977, Kofron 1978), water birds (Kushlan 1973), spiders (Suhr and Davis 1974), and fishes such as black basses and gars (Hunt 1953).

Length

Conservation Status

NatureServe Global Status Rank

Global Status Last Reviewed

2003-02-21

Global Status Last Changed

1996-09-20

Distribution

Conservation Status Map

Global Range

G - 200,000-2,500,000 square km (about 80,000-1,000,000 square miles) - G - This species is native to most of south-central United States, north to Indiana and Illinois, west to Texas, south to southern Mexico, east to Mobile River system. Populations in the drainages of the Chattahoochee and Savannah rivers (Lydeard and Wooten 1991) possibly are native (Page and Burr 2011). See Walters and Freeman (2000) for information on the distribution of G. affinis and G. holbrooki in the Conasauga River system, where G. affinisi is widespread and native and G. holbrooki is apparently introduced and expanding its range. This fish is widely introduced in the western United States and throughout the world. Lynch (1992) reported that five or six populations from Georgia, Illinois, Tennessee and Texas were used for most introductions nationwide and worldwide. Within the United States, sources from Illinois, Tennessee and Texas were used to establish mosquitofish in the western half of the country. Therefore, most if not all populations in the western United States are G. affinis.

Global Range Code

Global Range Description

200,000-2,500,000 square km (about 80,000-1,000,000 square miles)

ELEMENT_GLOBAL.2.103578