LENGTH FREQUENCY DISTRIBUTION, ALLOMETRIC GROWTH AND MORPHOMETRIC CHARACTERISTICS OF Oreochromis niloticus FROM OVIA RIVER

Abstract

Oreochromis niloticus is one of the most widespread species in Africa. Its introduction around the world is of economic and social benefit especially in rural communities where they are caught from the wild or cultured in captivity. Length frequency distribution was used to estimate the age of this commercial fish species between May to October, 2012. A year old (1+) specimen had a total length in the size class of 100-121 mm. Other size classes whose total length measurements are (133-165 mm, 166-176 mm and 188-220 mm) corresponded to ages of (2+, 3+ and 4+) as stated. Significant relationships existed between total length and body weight measurements resulting in 'r' value of (0.88) for male and (0.813) for female. The regression coefficient ‘b’ for males was (1.903) while that for females was (1.887). Both values were less than three, indicating negative allometric growth. Characterization of lengths of body parts, otherwise known as morphometric measurement, revealed that there was a significant relationship between total length and lengths of other body part including: length of scales (0.599), right eye diameter (0.883), left eye diameter (0.571), otoliths (0.881) and body weight (0.594) for males. Likewise in female specimens, the opercula bone (0.666) and otoliths length (0.814) showed significant relationships with total length of the fish. This study has shown that it is possible to age Nile Tilapia using length frequency distribution. Therefore length frequency distribution, in conjunction with other methods could also be investigated in further studies for the aging of same fish species in other water bodies as well as their investigation in other fish species, for a better understanding and management of the lives of fishes and fish populations.