Morphological variation of Nile tilapia populations from major water bodies of Uganda

Abstract

With increasing demand for improved farmed Nile tilapia (Oreochromis niloticus) fish seed, there
is heightened demand for quality and proven broodstock by hatchery operators throughout the
country and in the East African region. Uganda, fortunately, is endowed with vast natural Nile
tilapia (Oreochromis niloticus) stocks in lakes Albert, Edward and George, as well as in Albert Nile
River. To aquaculturally benefit from the different attributes of different stocks/strains, it is
important to establish the existing strains in a manner that is phenotypically discernible where
such differences are apparent. In this study, we used a suite of morphological traits to identify
strains of Nile tilapia among 425 individuals sampled from the four major water bodies, lakes –
Albert, Edward-George, Kyoga and Victoria. Morphological variation was investigated using
multivariate approaches including principal component analysis, discriminant analysis and
cluster analysis of 22 morphometric characters. These analyses indicated that there was high
morphological variation among the different populations of Nile tilapia and the fish could be
grouped into their respective sampled areas based on these morphological differences. Most of
the variation (86.97%) was associated with the fish body size, the peduncle length and the interorbital distances. Findings imply that there are four major Nile tilapia strains in Ugandan waters
that will be subjected to aquaculture performance evaluation before being used in the genetic
improvement programme to produce improved Nile tilapia fish broodstock/seed for use in fish
farming. Differences among populations may reflect genetic differences and/or environmental
factors.