THE ECOLOGY OF SCHILBEID FISH IN RIVER ASE, SOUTHERN NIGERIA

The ecology of schilbeid fish was studied in River Ase, Southern Niger ia, for a period of two years from March 1982-February 1984. The speci es recorded were Eutropius niloticus (RUPPELL) 1829, Schilbe cf. mystu s (LINNE) 1758, Physailia pellucida BOULENGER, 1901 and Eutropiellus b uffei GRAS, 1960. These species accounted for 12.4% by number, and 4.7 % by weight of all fish captured. E. niloticus and S. cf. mystus were the important species making up 85.2% by number, and 94.7% by weight o f all schilbeids caught. The seasonal variations in the abundance of E . niloticus and P pellucida showed that these species were migratory, while S. cf. mystus was a resident in the river. Both E. niloticus and P. pellucida showed a diel pattern of abundance in catches, while no distinct pattern of diel variation was recorded for S. cf. mystus. The spatial distribution of E. niloticus, S. cf. mystus and P. pellucida was heterogeneous within the study stretch. E. buffei was a rare speci es. The ecology of schilbeids in River Ase has been discussed and comp ared with the findings of earlier studies conducted in River Niger and Lake Kainji in Northern Nigeria.