Feeding habits and relative condition factor of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) (Pisces: Cichlidae) in Damte Reservoir, Southern Ethiopia

Abstract

The aim of the present study was to assess the feeding habits and relative condition factor of the Nile tilapia (Oreochromis niloticus (Linnaeus, 1758) in Damte Reservoir. A total of 584 O. niloticus samples were collected from two locations of the Reservoir based on their ecological differences. To diversify the sampling size, O. niloticus samples were additionally randomly selected from the fishermen's landings during four months of the dry season (February to May) and four months of the wet season (June to September). The collected data were summarized using descriptive statistics and analyzed with Microsoft Excel 2010 and SPSS v27 software. The diet compositions were expressed based on frequency of occurrences and volumetric contributions. From the total fish samples, 371 (63.53%) contained food in their stomachs, while 213 (36.47%) stomachs were empty. Detritus, macrophytes, and phytoplankton were the most frequently occurred food categories with relatively high volumetric contributions in the stomachs of fish. Notable changes were observed in the contributions of detritus, macrophytes, and phytoplankton, where their volumetric contributions increased with fish size. The major food categories remained consistent between seasons, though their volumetric contributions varied. The mean combined relative condition factor (Kn) value was 1.14 ± 0.014 for mixed sexes of O. niloticus. From the results of the present study, O. niloticus is an omnivore feeding on a wide range of food categories in Damte Reservoir. Female O. niloticus had higher mean Kn values than males, but the difference was not statistically significant (p > 0.05). Based on this finding, it is recommended to conduct further detailed studies to keep the overall conditioning of O. niloticus from the Reservoir.