Gambusia affinis (poisson)

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Nom taxonomique: Gambusia affinis (Baird and Girard, 1853) Synonymes: 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) Noms communs: 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) Type d'organisme: poisson Gambusia affinis est un petit poisson d’apparence inoffensive, originaire des eaux douces de l’est et du sud des Etats-Unis. Il est devenu un problème dans de nombreux cours d’eau à travers le monde, suite à son introduction, le siècle dernier, comme agent de lutte biologique contre les moustiques. En général, il s’est avéré moins efficace que les prédateurs indigènes de moustiques. Grand prédateur, ce poisson mange les oeufs des poissons à valeur commerciale et s’attaque et met en péril les espèces indigènes rares de poissons et d’invertébrés. Une fois établie, la gambusie est très difficile à éliminer, aussi le meilleur moyen de réduire ses effets est de prévenir à l'avenir sa propagation. L’une des principales causes de sa propagation persite, à savoir son introduction intentionnelle par les agences de lutte contre les moustiques. G. affinis est étroitement apparenté à G. holbrooki, qui a été autrefois classé comme une sous-espèce. Leur apparence, leur comportement et leur impacts sont presque identiques et ils peuvent donc être traités de la même façon en ce qui concerne les techniques de contrôle. Les mentions de G. affinis en Australie font en réalité références en réalité à G. holbrooki. Description 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). Espèces semblables Gambusia holbrooki, Poecilia latipinna, Poecilia reticulata, Xiphophorus maculatus More Se rencontre dans: cours d'eau, estuaires, lacs, zones humides Description de l'habitat 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). Mosquitofish 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). Most abundant in lower reaches of streams, where it inhabits brackish, standing to slow-flowing water.Most common in vegetated ponds and lakes, backwaters and quiet pools of streams (FishBase, 2003). Impacts globaux Adult Gambusia affinis are extremely aggressive and attack other fish, shredding fins and sometimes killing them. Controversy has followed the introduction of mosquitofish, 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 mosquitofish has also been shown to alter zooplankton, insect and crustacean communities (McDowall, 1990). Mosquitofish are potential hosts of helminth parasites, which have been transmitted to native fishes (FishBase, 2003). Utilisations Used as live food for carnivorous aquarium fishes and also used as mosquito control (FishBase, 2003). Notes Gambusia affinis is extremely similar to the closely related Gambusia 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). Distribution géographique 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. Informations pour la gestion de l'espèce Chemical: The poison rotenone, which works by inducing hypoxia in fish, may be used to eliminate mosquitofish 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). Alimentation Feeds on zooplankton, small insects and detritus, (FishBase, 2003). Reproduction Live-bearer. Several times a year mosquitofish 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). Stades du cycle de vie Males mature at about 21mm long and a month old; females at 28mm and six weeks old (McDowall, 2000) Cette espèce figure sur la liste de l’UICN des 100 espèces parmi les plus envahissantes au monde Révisé par: Major update under progress Sources principales: FishBase, 2004. Species profile Gambusia affinis Mosquito fish Compilé par: IUCN/SSC Invasive Species Specialist Group (ISSG) To contribute information, please contact Shyama Pagad. Dernière mise à jour: Tuesday, 11 April 2006