SOME GENETIC VARIABILITY OF WILD AND CULTURED POPULATIONS OF CLARIID CATFISH CLARIAS GARIEPINUS (BURCHELL 1822) BROODSTOCKS

Abstract

The present study was undertaken to determine the genetic differences between cultured and farmed populations of Clarias gariepinus in Southwest, Nigeria. Three wild populations from River Osun, Owena, and Agbabu and three farmed hatchery-bred populations from Akure, Ilesa and Ado-Ekiti, were analysed for their morphological and genetic differences. Life specimens, comprising forty individual, from each location were collected and kept in six concrete tanks (2x1x1m3) at Teaching and Research Farm of Fisheries and Aquaculture Department, Federal University of Technology, Akure for three days. Fifteen morphometric and four meristic parameters were measured. The morphometric characters were standard length (SL), total length (TL), caudal length (CL), head length (HL), body height (BH), caudal peduncle height (CPH), inter-orbital distance (IOD), ocular diameter (OD), pre-anal length (PL), pre-dorsal length (PdL), and head height (HH), dorsal and pectoral fins distance (DPD), pectoral and pelvic fins distance (PPD), pelvic and anal fins distance (PAD), dorsal and anal fins distance (DAnD). While the meristic characters were pelvic fin, pectoral fin, anal fin and dorsal fin rays. These were subjected to both Principal Component Analysis (PCA) and Canonical Variate Analysis (CVA). Five grams (5g) of muscle were taken from each specimen and assessed for their proximate composition, minerals content, fatty and amino acids profile. Blood samples were also obtained and used for Sodium Dodecyl Sulphate Polyacrylamide Gel (SDS-PAGE) for the protein profile and randomly amplified polymorphic DNA (RAPD) for DNA analysis. The CVA analysis showed overlapping clusters in Esaodo, Owena, Akure and Agbabu populations and across Ilesa and Ado-Ekiti. The PCA analysis showed that, the first principal component (PC1) due to variation in the total length (TL) and standard length (SL) accounted for 68% of the total variation while PC2, PC3 and PC4 accounted for 14%, 8% and 5% of the total variation respectively. The loading on PC4 revealed pectoral fin rays and pelvic fin rays to have contributed to 5% variation between populations of C.gariepinus. A significant difference was observed in proximate composition of C. gariepinus in both wet and dry matter bases. The moisture contents in muscle of cultured C. gariepinus was higher (5.75± 0.07) compared to wild C. gariepinus (5.57 ± 0.10%). The average protein contents in cultured C. gariepinus was observed to be higher 69.35±0.08% than wild C. gariepinus (67.23±0.07 %.). In wild C. gariepinus, lipids contents was lower (16.03 ±0.08%) but high in farmed fish (18.61 ±0.09%). The total ash contents in wild C. gariepinus were 9.15±0.07% and 8.41±0.08% in farmed. Wild and culture fish were found to differ in their organoleptic properties, differences in taste were found between sample locations and between wild and cultured C. gariepinus (p ˂0.05). Result reveals that consumers’ preference for wild C. gariepinus compared to cultured type. The amino acids (a.as) profile showed little disparity in quantity of wild and cultured C. gariepinus. Seventeen amino acids were analyzed, 11 amino acids (Threonine, Valine, Methinione, Leucine, Tyrosine, Phenylalanine and others higher) had value in wild fish compared to cultured C. gariepinus. No significant difference was noticed in the mean values of amino acids from wild 4.21 compared to cultured 4.16 C. gariepinus It was also observed that the percentage of saturated fatty acids like C16:0 and C18:0 was higher (56.24%) in cultured C. gariepinus compared to the wild stocks (44.53%) and this was also observed in unsaturated fatty acids: C39:1,C19:1,C19:2 and C22:1 (79.46%) in wild and cultured type (54.03%). The protein profile produced two clusters which may indicate divergence of the species in