Notes on the ecology of fishes of the genus Aphanius and Gambusia affinis in Southern Iraq

Abstract

SUMMARY. The ecology of three commonly occurring cyprinodonts, Aphanius dispar (Ruppell), A. sophiae (Heckel) and A. mento (Heckel) was studied in the Lower Mesopotamian Plain of Iraq. These fishes are chiefly herbivorous, live in the same habitat and generally take the same food, although the dentition of the jaw and pharynx in A. dispar differs from that of A. mento and A. sophiae. The gut contents were mostly filamentous algae. In laboratory experiments all three species ate Gambusia embryos. A. dispar and A. sophiae ate mosquito larvae whereas A. mento did not. All three species were infected with a cestode parasite which prevented development of female ovaries. The behaviour of the three species was different. Both A. dispar and A. sophiae form schools, swimming and feeding together. In their natural habitat, males and females of A. dispar were in separate schools. A. mento did not form schools; the males of this species displayed aggressive behaviour. Some observations were also made on Gambusia affinis (Baird & Girard).