Title: Distribution and abundance of Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) in Lake Victoria, Uganda.

This report is based on preliminary assessment of Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) in the shallow parts of the Ugandan sector of Lake Victoria. The assessment was carried out in the period of July-December 1999. A total of 106 hauls were taken on 59 stations. A total number of 13678 Nile perch with a mean length of 22.0 cm (s =14.1) and 805 Nile tilapia with mean length of 29.4cm (s = 14.9) were observed. Maximum CPUE for the study period was 406.3 kg/hr for Nile perch and 105.7 kg/hr for Nile tilapia. Total mortality (Z) of Nile perch and Nile tilapia, estimated using the linearized catch curve equation from von Bertalanffy growth equation, was 1.65 and 0.74 respectively. Natural mortality (M) for Nile perch was 0.34 and Nile tilapia 0.56 calculated using Pauly´s empirical formula. The exploitation rate for Nile perch was higher as to compared to the Nile tilapia, hence the estimates were 0.79 and 0.24 respectively. Biomass estimation of the two species was done based on the estimated swept area method. The biomass of L. niloticus and O. niloticus in the Ugandan part of Lake Victoria in the period of July-December 1999 was estimated 43962 t and 3297 t respectively.