The interac tion of living organisms with the disturbed environment as often manifested in distinguishing morphological features . Therefore, analyzing species in these disturbed environments and comparing them to the source populations may serve as a study system to investigate responses to environmental disturbances. In the present work, we analyzed morphological variation of Oreochromis niloticus from two reservoirs and compare with a river within the south west Nigeria, with a view to know the effect of environment on fish morphology.
A total of one hundred and nine individual samples of Oreochromis niloticus were obtained from the study locations for morphological studies. M orphometric and meristic characteristics of the fish were measured using calibrated measuring board aided with ruler and a pair of divider/caliper. Fifteen morphometrics and six meristics characters were considered for the study. Data were analysed using Paleontological Statistical Test (PAST) software .
The study indicated that there w ere variations morphologically in the fish from the environments and that, not all the morphological features of O. niloticus in the study areas contributed significantly to variations observed. The scatter diagram, indicated that fish samples from Awara and Egbe reservoirs have morphometric features that are more related than to those from Ogbese River . The observed variation with the meristic characters occurred mostly within the entire region. This study indicates that the water reservoir seems to be an important factor influencing morphological variation in O. niloticus.