Morphological variability of Tilapia zillii (Gervais, 1848) from selected reservoirs in southwestern, Nigeria

Abstract

Tilapia zillii is one of the dominant cichlids in southwestern reservoirs of Nigeria. Morphological variation was investigated among three populations (Opa, Ero and Asejire reservoirs) of this species using univariate and multivariate analysis. This was with a view to determining the pattern of morphological differentiation among them. Measurements of twenty five morphometric characters and six meristic counts were recorded on fifty specimens each. Univariate analysis of variance showed significant differences (p< 0.005) between the means of the three groups for 20 out of 25 morphometric measurements while there was no significant difference between the means of the three groups for most of the meristic characters. Canonical variate analysis results for the morphometric data shows overlap of clusters of fish specimens from Opa and Ero Reservoirs as well as Ero and Asejire Reservoirs. However, there was no overlap between T. zillii samples from Asejire and Ero Reservoir. Results established heterogeneity in morphology among populations of Tilapia zillii inhabiting the three reservoirs based on univariate and multivariate analysis of the morphometric characters only. The meristic characters could not delineate the three populations. The study therefore concluded that populations of T. zillii from Ero and Asejire reservoirs were phenotypically separable populations of the same species while those from Opa reservoir are somewhat morphologically related to both of them.

Keywords: Meristics, Morphometrics, Phenotypically, Reservoir, Variation