ECOMORPHOLOGICAL INDIVIDUAL VARIATION IN A POPULATION OF HAPLOCHROMIS-NYEREREI FROM THE TANZANIAN PART OF LAKE-VICTORIA

Intraspecific morphological variation among a population of Haplochrom is nyererei (Teleostei, Cichlidae) from Lake Victoria was investigated . Three main groups of variables were used: general shape, outline of the head. and trophic group (intestinal length, stomach contents, teet h and jaw shape, lower jam length and width). Fishes were arranged int o four groups: G1, large males with a prominent bump on the head, a th ickset body and anatomical structures related to a strictly insectivor ous diet: G2, large males lacking a bump on the head but mure or less thickset and showing anatomical structures related to omnivorous feedi ng habits, though Favouring insects; G3, males and a Few females with a slight bump on the head. a slender body shape and showing anatomical structures related primarily to a herbivorous tendency; and G4, femal es and a few small males without a bump an the head, a slender body an d showing anatomical structures related to an omnivore with herbivorou s tendencies. Several hypotheses related to behaviour are presented pa rtly to explain the intraspecific variation observed. Differences betw een individuals could arise as a result about the establishment of dom inance and territory in males. (C) 1996 The Fisheries Society of the B ritish Isles.