Feeding habits and some other biological aspects of Oreochromis niloticus (L.) and Cyprinus carpio (L.) in Lake Ardibo

Abstract

Ethiopian freshwater bodies support a substantial fishing population; however, their sustainable utilization has been limited due to the lack of comprehensive scientific information on the feeding ecology, reproductive biology, and length–weight relationships (LWRs) of commercially important fish species. This study investigated the feeding habits and selected biological characteristics of Oreochromis niloticus and Cyprinus carpio in Lake Ardibo from June 2022 to September 2023 based on monthly sampling campaigns. Fish specimens were collected using gillnets and hooks. Selected physicochemical parameters of the water, including temperature, pH, and dissolved oxygen, were measured and found to be within ranges suitable for fish survival. The LWRs of both species indicated nearly isometric growth patterns. The mean condition factor (K) was 1.77 for O. niloticus and 1.75 for C. carpio, with no significant differences between sexes (P > 0.05). Both species exhibited omnivorous feeding strategies, consuming a wide range of prey items. In O. niloticus, detritus occurred in 40% of the stomachs and contributed 41.38% of the total food volume, while Microcystis was present in 73.33% of the stomachs and accounted for 62.99% of the volume. In C. carpio, detritus and diatoms contributed 49% and 33.2% of the total food volume, respectively. Based on the Index of Food Preponderance (%IFP), detritus constituted 46.40% and 63.79% of the diet in O. niloticus and C. carpio, respectively. Ontogenetic analysis revealed an increase in the contribution of plant-origin diets with fish size in O. niloticus. Overall, the results indicate that both species adopt an omnivorous feeding strategy with a tendency toward detritivory and herbivory in larger individuals.