Abundance and Micro-Distribution of Cichlid Fishes on a Rocky Shore of Lake Tanganyika

Abstract

Every species of rock dwelling cichlid fishes were counted with help of SCUBA at Luhanga in the northwestern part of Lake Tanganyika in 1980. In this area rocky substrate was prominent especially in shallow bottom, while stone, rubble, gravel or sandy substrates were patchily scattered among rocks. About 7, 000 fishes of 38 species were counted in a quadrat (20x20 m ²). Plankton feeders (2 species) were most abundant (56%), omnivores (7 species) and Aufwuchs eater (15 species) composed of 21 and 18%, respectively. Numbers of zoobenthos feeders (8 species) and piscivores including scale eaters (6 species) were about 4%. Plankton feeders were gregarious, while species of the other feeding habits were exclusively distributed to other conspecific individuals. About a half number of species frequented on a specific substrate type as follows: Almost all Aufwucks eaters preferred strongly on rocks especially in shallow water layer and zoobenthos feeders had different preferences to substrate each other, showing repulsive distribution. Among another half number of species, 3 species adhered to shallow region and the rest species showed ubiquitous distribution without any substrate preference, and their number of individuals was small. It is characteristic that most piscivores (4 species), most omnivores (4 species) and a few zoobenthos feeders (2 species) were ubiquitous. Most species kept a distance from piscivores. Each set of two species of Aufwuchs eater and two species of omnivore often frequented together suggesting a cooperative feeding.