A group of zooplankton feeders of the genus Haplochromis (Cichlidae) in Lake Nyasa

Publication Type:Journal Article
Year of Publication:1960
Authors:Iles, TD
Journal:Annals and Magazine of Natural History
Volume:(13)2
Pagination:257-280
Date Published:05/1960
Abstract:

In her synopsis of the Cichlid fishes of Lake Nyasa Trewavas (1935) separated six species of Haplochromis which were distinguished by the possession of a strongly protractile upper jaw. Bertram, Borley and Trewavas (1942) grouped these species under the name "Utaka", the native name used at all places on the lake-shore, either for individual species, or for the group as a whole. They were further described as small fishes with a small and narrow mouth, small teeth and a protractile upper jaw so that when the lower jaw is depressed, the upper jaw shoots out to form a short tube; but this protractility was recognised as differing only in degree from that of other species of Haplochromis, and in the Utaka group itself it varied considerably. All the species were described as plankton feeders and this was thought to confirm the impression that they occurred in the surface waters over the whole area of the lake. Lowe (1952) also stated that they were zooplankton feeders, that they were probably open water species, but that they may move into shallower and more productive waters when spawning or when brooding young. It has been recognised that the six species listed by Trewavas in 1935 do not indicate the full complexity of the group. Bertram, Borley and Trewavas for instance (op. cit.) said that H. quadrimaculatus Regan (Regan, 1922) is probably a species complex, and Lowe (op. cit.) stated that many forms could not be assigned by her to any one species. Little was known of the general biology of the group and because of their potential economic importance, especially in the northern areas of the lake, a study of the Utaka group was undertaken as part of the programme of the Joint Fisheries Research Organisation which between 1953 and 1956 carried out a biological survey of this part of the lake.

Many forms were recognised, some of which are here described for the first time.

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