Comparative Analysis of Contaminability between Clarias gariepinus and Tilapia mariae

Abstract

Water, Clarias gariepinus and Tilapia mariae samples were collected from four (4) stations across the length of the Osse River between the periods of April, 2013 to September, 2014. Heavy metals (Iron, manganese, nickel and lead) and total hydrocarbons in water and fish tissues (gills, intestine and muscles) were tested using Atomic Absorption Spectrophotometer (Varian Techron Spectr AA – 10 Model; serial number 902 1318) and Agilent 6890N Gas Chromatograph - Flame Ionization Detector instrument (Model 6890) respectively. Much higher concentrations of all the contaminants (except lead) were detected in the intestine of Clarias gariepinus than the intestine of Tilapia mariae. This can be attributed to the fact that Clarias gariepinus- a demersal fish (bottom feeder) as opposed to Tilapia mariae (pelagic fish), must have been exposed to considerably high concentrations of heavy metals and total hydrocarbons (THCs) in the bottom of the river through foraging. The sequence of heavy metals and total hydrocarbons was the same in both fish species: Fe > Mn > THC > Pb > Ni as against the sequence in water: Fe > THC > Mn > Pb > Ni. The trend of the heavy metals and total hydrocarbons among the analyzed matrices was: Clarias gariepinus > Tilapia mariae > water. Despite the health risks (mainly of iron and manganese) observed in both species, no ecological risk was observed in the aqueous phase. This can be attributed to the significant bioaccumulation factors which are functions of their thresholds of essentiality. Results showed that Clarias gariepinus posed a higher level of health risk than Tilapia mariae. Furthermore, given that manganese alone contaminated the muscle of T. mariae while iron and manganese were the contaminants in the muscle of C. gariepinus, it is safer to consume the T. mariae than the C. gariepinus; particularly during the dry season.