Multivariate Analysis of Morphometric Parameters in Wild and Cultured Nile Tilapia Oreochromis niloticus

In order to evaluate the phenotypic variation between natural population and cultured stocks of Nile tilapia (Oreochromis niloticus Linnaeus, 1758), the intraand inter-population differentiations were analyzed using biometric approach. Thus, eight morphological measurements were taken from 300 specimens collected from Ismailia Canal (AB) as natural population and two cultured stocks from Kafr El-Shaikh (KE) and Fayoum (FA) Governorates. All specimens collected at juvenile stage in first generation which reared in the under environment al conditions. The univariate (ANOVA) and multivariate analyses (principal component analysis, PCA, and discriminant function analysis, DFA) showed a low variability among populations. The morphometric pattern observed in 3 stocks of Nile tilapia reflects variation primarily along three axes. Together these components accounted 81.20% of observed variation. Three characters were selected by step-wise discriminant function analysis on morphometric data. This study shows the existence of morphological differentiations between subpopulations derived from a single gene pool that have been isolated in separated sites for several decades although bred in relatively similar environments.