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   Gambusia affinis (fish)  français     
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      Mosquitofish pair (Photo: Bob McDowall) - Click for full size   Gambusia affinis (Photo: WikiMedia Commons) - Click for full size   Gambusia affinis (Photo: WikiMedia Commons) - Click for full size   Gambusia affinis (Photo: WikiMedia Commons) - Click for full size
    Taxonomic name: Gambusia affinis (Baird and Girard, 1853)
    Synonyms: Fundulus inurus (Jordan & Gilbert, 1882), Gambusia affinis affinis (Baird & Girard, 1853), Gambusia affinis (Baird & Girard, 1853), Gambusia gracilis Girard, 1859, Gambusia humilis Günther, 1866, Gambusia patruelis (Baird & Girard, 1853), Haplochilus melanops Cope, 1870, Heterandria affinis Baird & Girard, 1853, Heterandria patruelis Baird & Girard, 1853, Zygonectes brachypterus Cope, 1880, Zygonectes gracilis (Girard, 1859), Zygonectes inurus Jordan & Gilbert, 1882, Zygonectes patruelis (Baird & Girard, 1853)
    Common names: Barkaleci (Albanian), Dai to ue (Cantonese-Hong Kong), Gambusia, Gambusie (French-Canada), Gambusino (Spanish), Gambuzia (Portuguese), Gambuzia pospolita (Polish), Gambuzija (Russian-Ukraine), guayacon mosquito (Spanish), Isdang canal (Tagalog), Kadayashi (Japanese), Koboldkärpfling (German), Kounoupopsaro (Greek), live-bearing tooth-carp (English-Hong Kong), Mosquito fish (English), Obyknovennaya gambuziya (Russian), pez mosquito (Dominican Republic), San hang ue (Cantonese-Hong Kong), Silberkärpfling (German), tes (Cantonese-Hong Kong), Texaskärpfling (German), Topminnow (English-Hong Kong), western mosquitofish (English), Western mosquitofish (English-USA)
    Organism type: fish
    Gambusia affinis is a small fish native to the fresh waters of the eastern and southern United States. It has become a pest in many waterways around the world following initial introductions early last century as a biological control agent for mosquitoes. In general, it is considered to be no more effective than native predators of mosquitoes. The highly predatory mosquito fish eats the eggs of economically desirable fish and preys on and endangers rare indigenous fish and invertebrate species. Mosquito fish are difficult to eliminate once established, so the best way to reduce their effects is to control their further spread. One of the main avenues of spread is continued, intentional release by mosquito-control agencies. G. affinis is closely related to he eastern mosquito fish (G. holbrooki), which was formerly classed as a sub-species. Their appearance, behaviour and impacts are almost identical, and they can therefore be treated the same when it comes to management techniques. Records of G. affinis in Australia actually refer to G. holbrooki.
    A stout little fish, the back a little arched in front of the dorsal fin and the belly deep in front of the anal. The head is large with a flattened upper surface, the mouth small, upturned and protrusible, and not reaching as far back as the front of the eyes. The eyes are very large relative to the body. The single, soft-rayed dorsal fin is short-based, high and rounded, while the caudal peduncle is long, deep and compressed, and the caudal fin is rounded. The head and trunk are covered with large scales and there is no lateral line. The back is a greenish olive to brownish, the sides grey with a bluish sheen, and the belly a silvery white. A well-defined black spot on the upper rear abdomen is surrounded by a golden patch above and behind the vent. In mature females there is also a black patch above and somewhat forward of the vent. The ventral surface of the head is a steely blue with a diagonal chin stripe below the eyes. The eyes are greyish to olive, the dorsal fin has small black spots, and the caudal fin has several indistinct cross rows of small black spots. The anal, pelvic and pectoral fins are a translucent pale amber. (McDowall, 1990). Males grow to 40mm in length, while females reach 70mm long (FishBase, 2003).
    Similar Species
    Gambusia holbrooki, Poecilia latipinna, Poecilia reticulata, Xiphophorus maculatus

    Occurs in:
    estuarine habitats, lakes, water courses, wetlands
    Habitat description
    Benthopelagic; non-migratory; lives in fresh and brackish water with a pH range of 6.0 - 8.0 and usually at temperatures between 12 - 29°C (FishBase, 2003). Mosquito fish are a remarkably hardy species, surviving in waters with little oxygen, in high salinities (including twice that of sea water) and temperatures of up to 42°C for short periods (McCullough, 1998). They are most abundant in lower reaches of streams, where they inhabit brackish, standing to slow-flowing water. They are most common in vegetated ponds and lakes, backwaters and quiet pools of streams (FishBase, 2003).
    General impacts
    Adult Gambusia affinis are extremely aggressive and attack other fish, shredding fins and sometimes killing them. Controversy has followed the introduction of mosquito fish, as they have been accused of being little better at destroying mosquitoes than native fish species, as well as being responsible for eliminating many of these same species (Myers, 1965; Haas et al., 2003). Selective predation by mosquito fish has also been shown to alter zooplankton, insect and crustacean communities (McDowall, 1990). Mosquito fish are potential hosts of helminth parasites, which have been transmitted to native fishes (FishBase, 2003).
    Used as live food for carnivorous aquarium fishes and also used as mosquito control (FishBase, 2003).
    Gambusia affinis is extremely similar to the closely related G. holbrooki, and until relatively recently they were classed as sub-species rather than distinct species. As such, their impacts and behaviour are virtually identical, and the same management techniques will work for both species.

    Although hybrids between G. holbrooki and G. affinis can occur, they are unusual in natural populations (Wooten and Lydeard 1990).

    Geographical range
    Native range: Southern USA and northern Mexico. Populations of G. affinis naturally occur in or near Mobile Bay and occupy drainages westward into Texas and Mexico (Wooten & Lydeard, 1990).
    Known introduced range: G. affinis has a near pan-global distribution and is thought to be the most widely introduced freshwater fish in the world.
    Introduction pathways to new locations
    Biological control: Widely introduced for mosquito control. (FishBase, 2003)
    Ship: Brought to New Zealand by ship. (McDowall, 1990)
    Taken to botanical garden/zoo: Survivors of the sea voyage to New Zealand were released into a pond in the Auckland Botanical Gardens. (McDowall, 1990)

    Local dispersal methods
    Other (local): Introductions to new locations within countries (FishBase, 2003)
    Management information
    Chemical: The poison Rotenone, which works by inducing hypoxia in fish, may be used to eliminate mosquito fish from small areas of permanent water. Rotenone is indiscriminate, so non-target species ideally need to be removed prior to its application. Fish affected by Rotenone come to the surface to seek oxygen, so any remaining non-target species may be removed at this stage (Willis & Ling, 2000).
    Feeds on zooplankton, small insects and detritus, (FishBase, 2003).
    Live-bearer. Several times a year mosquito fish produce moderate numbers of young, which are protected by the mother but which become immediately independent. Brood size is usually around 60 young, but large females can carry more than 300 (McDowall, 2000).
    Lifecycle stages
    Males mature at about 21mm long and a month old; females at 28mm and six weeks old (McDowall, 2000)
    This species has been nominated as among 100 of the "World's Worst" invaders
    Compiled by: IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Monday, 21 June 2010

ISSG Landcare Research NBII IUCN University of Auckland