The convict cichlid (Amatitlania nigrofasciata) is a fish species from the family Cichlidae, native to Central America also known as the zebra cichlid.Convict cichlids are popular aquarium fish and have also been the subject of numerous studies on fish behaviour.

The common name convict cichlid is, like the species name, derived from the vertical black stripes on the body which are reminiscent of the striped prison uniforms of British convicts. Similarly, the species epithet nigrofasciatus literally means “black-striped”.

Description

A young male convict cichlid showing the leucistic colouration
The wild-type of the species has 8 or 9 black vertical bars on a blue-grey body, along with a dark blotch on the operculum. Juvenile convict cichlids are monomorphic until they reach sexual maturity. The male is mostly gray with light black stripes along the body. Males are larger than females, and they have more pointed ventral, dorsal and anal fins which often extend into filaments. In addition, older males frequently develop vestigial fatty lumps on their foreheads. Unusually for fish, the female is more highly coloured. She has more intense black bands across the body, and pink to orange colouration in the ventral region and on the dorsal fin. The maximum standard length has been reported to be 10 centimeters, with total length near 12 centimeters (4.7 in). The body weight of the fish is about 34–36 grams (1.2–1.3 oz).Selective breeding has resulted in a leucistic strain, which lacks the dark barring of the wild type. These are known commonly as white convicts, pink convicts, gold convicts, and A. nigrofasciata “Kongo”. The leucistic colouration is caused by a mutation in an autosomal gene and is recessively inherited.

Range and habitat

A male convict cichlid caught on a hook and line, in the heated outflow of a coal powerplant in Victoria, Australia.
Convict cichlids are native to the lakes and streams of Central America. In particular, the species occurs along the eastern coast of Central America from Guatemala to Costa Rica, and on the western coast from Honduras to Panama. Convict cichlids prefer moving water, and are most frequently found in habitats with cover in the form of rocks or sunken branches. At four natural habitats of the convict cichlid in Costa Rica, the pH was found to range from 6.6–7.8, while carbonate hardness (KH) ranged from 63 to 77 ppm CaCO
3. The daily water temperature ranged from 26–29 °C (79–84 °F).[15] Convict cichlids can be relatively tolerant of cool water, allowing them to colonise volcanic lakes at elevations of 1,500 meters (4,900 ft).

Feral populations
The species also occurs outside its natural range, even being found in Australia, where it can be found in the warm effluent of power stations in Victoria, and in tropical Queensland. It has also been captured in Perth, Western Australia, although this initial capture also resulted in its eradication.[23] In addition to Australia, the species has been introduced to Réunion, Japan,Mexico, Colombia, Taiwan, and the USA.

Feeding

In natural habitats, the species has an omnivorous diet composed of plants, algae and various prey including small fish, crustaceans, insects and worms. The fish can protrude its jaw 4.2% of its standard length, allowing it to have a varied diet.Inferior social status and associated stress can affect digestive function in convict cichlids