Fish species and size distribution and abundance in different areas in Lake Victoria, Tanzania

Abstract

The study was carried out to investigate fish species distribution and abundance in different areas and size structure variations according to depth in Lake Victoria, Tanzania. Data were collected using a bottom trawl net during rainy and dry seasons in 2002. The results show that there were significant differences in catch rates between rainy and dry seasons (F (12, 12) = 2.69; p < 0.05). The rainy season recorded higher catch rates (36.25 - 106.61 kg/hr) than during the dry season (14.30 - 67.90 kg/hr). The haplochromines catch rates were higher during the dry season (11.08 kg/hr) than during the rainy season (7.72 kg/hr), however, the differences were not significant (2 = 0.60, df = 1, p > 0.05). The distribution of the fish species in different areas recorded a significant difference during the dry season (Q = 18.254, df = 8, P < 0.001), while during the rainy season the difference was not significant (Q = 10.667, df = 8, P > 0.001). Moreover, the results show that small individuals dominated in shallow waters at a mode ranging between 15 cm and 25 cm TL. Larger individuals dominated in deep waters recording a mode at 45.5 cm TL. The study therefore, suggests that in order to have a sustainable fishery, L. niloticus should actively be exploited at depths greater than 20 m where there are larger and mature individuals.

Tanzania Journal of Science Vol. 31 (1) 2005: pp. 73-82