Oreochromis mortimeri
Oreochromis mortimeri, the Kariba tilapia or kurper bream, is a species of cichlid, formerly classified as a Tilapiine cichlid but now placed in the genus Oreochromis, the type genus of the tribe Oreochromini of the subfamily Pseudocrenilabrinae. It is found in the rivers of south central Africa especially the middle Zambezi where it is endangered by the spread of invasive congener Oreochromis niloticus.
Description
Oreochromis mortimeri is greenish grey, green-blue or grey-blue marked with darker spots on each of its scales. The females and immature males often have 1–3 dark blotches in the middle of their flanks although these may only be visible as the fish dies. The breeding males are mainly iridescent, shading from blue-green to bronze and they have iridescent spots on their dorsal and caudal fins. The dorsal fin has a red margin that is not as obvious as it is in O. mossambicus, with a thin red band at posterior end of caudal fin, whereas that of O. mossambicus is noticeably wider. The jaws of mature males are obviously enlarged.Distribution
Oreochromis mortimeri is endemic to the middle Zambezi valley form the Cahora Bassa gorge to the Victoria Falls. Its distribution includes the Luangwa River and its tributaries. It occurs in Mozambique, Zimbabwe and Zambia.Biology
Oreochromis mortimeri is a schooling species which is predominantly diurnal. It is also tolerant of higher salinities. Its diet largely consists of filamentous algae and diatoms, and also includes some vascular plants, Dipteran larvae, other insects, cladocerans, copepods, shrimps, annelids and molluscs.The male makes a saucer-shaped depression with a raised mound in the middle as a nest situated within a breeding arena in water less than in depth. The male attracts the females to the arena using a courtship display. The female lays the eggs and they are fertilised by the male before she collects them in her mouth. The mouthbrooding females do not feed and may form shoals. The eggs hatch after around ten days but the larvae remain in their mother's mouth for a few more days. Once the yolk has been consumed the fry undertake brief feeding sorties, staying close to their mother and darting into her mouth when threatened. Around a fortnight after hatching the female releases the young fish in nursery areas of warm shallow water close to the banks, where the young fish group in small shoals in which they forage independently. The female then goes back to the breeding arena where she spawns again. Breeding occurs throughout the year.