ASSESSMENT OF GENETIC STRUCTURE OF CLARIAS GARIEPINUS, BURCHELL, 1822 POPULATION IN ASEJIRE LAKE

Abstract

Wild brood-stock is a major genetic reservoir for sustainable culture of Clarias gariepinus. This has been observed to be declining in major freshwater dams in Nigeria. There is inadequate information on factors responsible for this decline and their effects on genetic structuring of the fish resources in these dams. This study therefore investigated genetic structure of C. gariepinus in relation to environmental condition of Asejire Dam.

The Dam was spatially divided into Oyo State (OYS) and Osun State (OSS) strata. Thirty- eight sites were randomly selected, nineteen sites from each stratum. Water Quality Parameters (WQP) were sampled bimonthly in wet and dry seasons for 24months. The WQP selected were temperature, Dissolved Oxygen (DO), Total Hardness (TH) and Total Alkalinity (TA). Catchment area was assessed for indices of threat to environmental condition; Watershed Forest Degradation (WFD), frequencies of Partial Dam Gate Opening (PDGO) and Complete Dam Gate Opening (CDGO). Clarias gariepinus catches from fishermen’s landings were used to study genetic structure by examining variability in phenotypes and genotypes. Phenotypic data obtained were regrouped to subgroups of sex, size, and grades of Possession of Anteriorly Serrated Pectoral Spine (PASPS). Regrouped cases that had significantly different subgroups’ phenotypes were further screened for presence of Private Allele (PA), polymorphism of protein, DNA bands and genetic distance using standard procedures. Data were analysed using descriptive statistics, student’s t-test and cluster analysis.