CHARACTERISATION OF TILAPIINE SPECIES FROM SELECTED RESERVOIRS AND RIVERS IN THE NORTHERN REGION OF GHANA

Abstract

A study was carried out in selected water bodies in the Tolon, Kumbungu and West Mamprusi districts in the Northern Region of Ghana to distinguish between tilapiine species. Eighteen (18) morphometric characters were taken using calipers and a measuring board and eight (8) meristic counts were conducted using visual observation. Discriminant function analysis was employed to discriminate between the tilapiine species using the morphometric characters. AOAC procedures for analyzing proximate composition was used to obtain crude protein, dry matter, fat and ash content of the tilapiine species. Physico-chemical characteristics analysed included pH, temperature, nitrate, phosphorus, DO and chlorophyll ‘a’ concentration of water bodies. Three (3) tilapiine species; Oreochromis niloticus, Tilapia zillii and Sarotherodon galilaeus were identified. Meristic characteristics among the tilapiine species observed were not significantly different (P>0.05) for all meristic features considered except pectoral fin rays and pelvic fin rays and spines. Pectoral fin length, caudal fin length, head depth, and body depth were the morphometric characters that discriminated between the tilapiine species using the discriminant function analysis. The length-weight relationship for O. niloticus (2.288), T. zillii (2.287) and S. galilaeus (2.065) exhibited a negative allometric growth. Physico-chemical variables were similar for the water bodies. The crude protein levels for O. niloticus (48.14±2.26) was significantly higher compared to T. zillii (37.75±1.96) and S. galilaeus (38.76±3.12). There was significant difference in the dry matter and fat content of T. zillii (19.12±0.31; 2.31±0.59) and S. galilaeus (18.10±0.39; 1.46±0.53) respectively but no significant difference between the aforementioned species and O. niloticus (18.46±0.37; 2.00±0.39). Differences in colorations, length-weight relationship, pectoral fin length, caudal fin length, head depth, body depth and all the meristic characteristics considered except pelvic fin rays and spines were able to differentiate between the tilapiine species harvested from the selected rivers and reservoirs. Conducting a genotypic characterisation is recommended.