Describing the Body Shape of Oreochromis niloticus (Linnaeus, 1758) Populations in Bukidnon, Philippines Using Relative Warp Analysis

Samples of Oreochromis niloticus were collected from the two selected lakes in Bukidnon, Philippines namely Lake Apo and Pulangui Lake and were subjected to geometric morphometric analysis to describe the body shape variations. Significant degrees of variations were detected both within and between populations which were elucidated by multivariate analysis of variance (MANOVA), canonical variate analysis (CVA) and discriminant function analysis (FDA). Sexual dimorphism was clearly detected between the two sexes in both populations, thus shape variation can be accounted to different evolutionary role between sexes. Additionally, geographic isolation and varying level of genepool could be the factors in the variation observed in populations between the two lakes. Thus, the present study demonstrated the capability of geometric morphometrics analysis to distinguish and describe the variations in body shape existing within and between populations of O. niloticus. Further studies on the genetics of shape variations are recommended to advance the knowledge and understanding about the divergence in the species which would greatly contribute to its conservation and to aquaculture management strategies.

Keywords: Canonical variate analysis, geometric morphometrics, Lake Apo, Pulangui Lake, relative warps, sexual dimorphism