The Mosquito Fish (Gambusia affinis)

by James K. Sayre

28 August 2002 and 23 July 2003

Mosquito Fish - Gambusia affinis - family: Poeciliidae (Livebearer Family).

[Etymology: mosquito Spanish mosquito, diminutive of mosca, Latin musca, a fly + fish Middle English fish, fisk, Old English fisc, compare: Old Frisian fisk, fisc, Old Norse fiskr, German, fisch, Dutch visch, so named because its chief food is mosquito larvae and pupae].

This is a small fish that grows to about two inches long. (Actually, the larger female grows to two inches in length, while the shorter male grows to only about one inch in length). It is silvery-olive-green in color and is somewhat transparent. Each of its small scales is fringed in black. It is found living in slow-moving to still fresh water and also in brackish water in North America. It bears from one dozen to three dozen live fry (young), which are about one-fourth inch in length. Its offspring are able to reproduce themselves in about thirty days. It eats mosquito larvae and pupae, as well as other aquatic insects, small crustaceans and algae. It is preyed upon by the Large-mouth Bass. Native to central and southern United States, Mexico and Central America. Native to California. Sometimes kept by fish fanciers. Also bred commercially for its appetite for mosquito larvae and pupae. Also bred commercially as a bait fish. Also sometimes put into backyard ponds to keep down the mosquito population. It has also been introduced into waters in other parts of the world to keep down the mosquito population; in fact, some authorities consider it the most widely distributed fish in the world. Some biologists and fish fanciers consider the Mosquito Fish to be quite aggressive in its behavior towards other species its own size or smaller. Golden and Albino varieties have been developed by fish fanciers. Some biologists have classified the Mosquito Fish living east of the Mississippi River as a separate species: Eastern Mosquito Fish (Gambusia holbrooki). Note: tap water needs to be chemically treated to neutralize any toxic chloramines (chemicals which have been added by water treatment facilities to kill bacteria) before being added to any pond that will hold Mosquito Fish. When I released about a half dozen Mosquito Fish into my small backyard pond in the afternoon, by the morning almost all of the Mosquito larvae had been consumed; the few that remained were in the shallowest water which was too low for the Mosquito Fish to enter.

Other names: Gambusia, Guppy, Potgut Minnow, Western Mosquito Fish.

References:

McClane, A. J., Editor, McClane's Field Guide to Freshwater Fishes of North America, 1978. New York: Holt, Rinehart and Winston.

Palmer, E. Lawrence, Fieldbook of Natural History, 1949. New York: McGraw-Hill Book Company, Inc.

Reid, George K., Pond Life: A Guide to Common Plants and Animals of North American Ponds and Lakes, A Golden Nature Guide, 1967. New York: Golden Press, Western Publishing Co., Inc.

Wernert, Susan J., Reader' Digest North American Wildlife, 1982. Pleasantville, New York: Reader's Digest Association.