Reproductive biology and feeding habits of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) (Pisces: Cichilidae) in Lake Boyo, Ethiopia

Abstract

Lake Boyo (Fig. 1) is among the few lakes hidden behind the major lakes of Central Ethiopian Rift Valley Region. It is a shallow, turbid and an open lake. Neither fishery activity nor fishery research has ever been conducted before  in Lake Boyo. This research was conducted to provide baseline information on the reproductive biology and feeding habits of O. niloticus. It was conducted from May 2021 to September 2022.  A total of 379 (197 males and 182 females) samples of O. niloticus were collected using gill nets of 6, 8 and 10 cm mesh size and beachseine of 6 mm mesh size. The results indicated that the sex ratio (Male: Female) was 1: 0.92 (p> 0.05). Length at first sexual maturity was 10.0 cm (TL) for males and 7.7 cm (TL) for females. Fecundity ranged from 216 to 1,157 eggs per fish. O. niloticus breeds throughout the year in the lake and the peak breeding months were from July to September and February to March. The length to weight relationship for males was 3.04, females 3.18 and combined sexes 3.12 and showed slight positive allometric growth pattern. The stomach content analysis showed that detritus, macrophytes and phytoplankton were the major food items while insects and zooplankton were less important. According to this  study, it was concluded that O. niloticus is omnivorous. Further research should be carried out on the phytoplankton primary productivity and phytoplankton biomass of the lake for fish production.