The feeding ecology of schilbeid catfishes in river Ase, Niger delta, Southern Nigeria.

Abstract

The feeding ecology of Parailia pellucida (Boulenger, 1901), Eutropius niloticus (Rϋppel, 1872) and Schilbe mystus (Linnaeus, 1756) were investigated for two years (March, 1982-February, 1984) in River Ase, Niger Delta, southern Nigeria. A cyclic pattern of fish sampling was used and fish samples were collected from 0600-0900, 0900-1200, 1200-1500, 1500-1800, 1800-2100, 2100-2400, 2400-0300, 0300-0600 (hrs) using various fishing gear. Percentage food items and condition factors (kf) were calculated for each species. Feeding habits in relation to size groups, diel and monthly variations in feeding intensity were described for Eutropius niloticus and Schilbe mystus which had adequate data. The three species P. pellucida, E. niloticus and S. mystus were omnivorous surface feeders. They consumed more food items in the dry season than during the rainy season. Diel variations in feeding habit occurred both day and night with higher intensity at night especially between the hours of 9p.m. and 12 midnight. S. mystus is both day and night feeder. The medium size group of E. niloticus consumed a wider variety of food items than the small and large size groups. S. mystus consumed almost the same food items in both dry and rainy seasons. In the three size groups, most food items were selectively consumed indicating gape size as a limiting factor. The condition factors (kf) of the three species were above 1 indicating well being. Some aspects of the feeding ecology of the three schilbeid catfishes have been discussed and the results compared with the results of earlier investigations conducted elsewhere.

Key words: schilbeidae, feeding ecology, diel variation, seasonality