Diet composition, ontogenetic dietary shifts and morphometric relationships of the Nile barb Barbus bynni (Forsskl, 1775) (Pisces: Cyprinidae) in Lake Abaya, Ethiopia

Abstract

Food and feeding habits of Barbus bynni (Forsskål, 1775) were studied in Lake Abaya, Ethiopia, from January to February, 2010 (dry season) and May to June, 2010 (wet season). From a total of 292 fish samples, 251 (86.0%) contained food in their guts. Macrophytes, insects and detritus were the dominant food items both during the dry and wet seasons. Macrophytes and detritus occurred in 78.1 and 73.3% of the guts, and constituted 30.4 and 29.3% of the total food volume, respectively while insects occurred in 72.5% of the guts and accounted for 29.2% of the total volume. Zooplankton occurred in 37.5% of the guts but they constituted only 4.6% of the total volume of food categories. No seasonality in diet was observed, however, there was an ontogenetic change in diet. In juveniles, the contribution of food of animal origin was relatively high, whereas in adults the contribution of plant materials was dominating. The relationships between total length (TL) and total weight (TW) of males, females and both sexes combined were curvilinear and statistically significant (P < 0.001). The relationships between TL and fork length (FL), TL and standard length (SL) and FL and SL were all linear and statistically significant (P < 0.001). The growth pattern of B. bynni in Lake Abaya was allometric because the slope of the relationship (b) was 3.25, which is a value considerably higher than 3. Key