Gambusia affinis ~ Mosquito-fish

The mosquitofish is a species of freshwater fish indigenous to the Mississippi River in the USA. It is listed as one of the world’s worst invasive species. The name ‘mosquitofish’ was given because the diet of this fish predominantly consists of large amounts of mosquito larvae (as well as other invertebrate larvae); an adult female can consume hundreds in a day.
Its invasive status in South Africa is NEMBA Category 1b in national parks, provincial reserves, mountain catchment areas and forestry reserves declared in terms of the Protected Areas Act. NEMBA Category 2 for breeding for the purpose of feeding stock for zoos and animal breeders. NEMBA Category 3 for all other discrete catchment system in which it occurs.
Mosquitofish can be spread during floods and through unintentional relocation when it is inadvertently transported in aquatic equipment, such as nets, boats and fishing gear.
Why is it a problem? Adults are extremely aggressive and attack other fish, shredding their fins and sometimes killing them. They are known to prey on eggs, larvae and juveniles of various fishes, including largemouth bass and common carp. They are also known to prey on adults of smaller species.
Mosquitofish is a small, live-bearing fish, dull grey or brown, with no bars or bands on the sides, and a rounded tail. The body is short and the head flattened, with the mouth pointed upward for surface feeding. It may have a large dusky to black teardrop marking beneath its eye, but this marking is sometimes reduced. Females have a rounded, small anal fin and grow to about 6-7cm. Males grow to about 4cm. Habitat: It occurs in a variety of freshwater and protected brackish environments. It preferentially occupies vegetated ponds and lakes, backwaters and quiet pools of streams. It is most often encountered in standing or slow-flowing waters.
The maximum age of mosquitofish is four years. They prefer temperatures between 12-29 degrees Celsius. However, in deep enough water they are able to reduce activity and go into a hibernation-like state.

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