Assessment of heavy metal concentrations as indicator of pollution in Clarias gariepinus (African catfish) of Warwade reservoir, Dutse, Jigawa State-Nigeria

Abstract

Pollution status of Warwade reservoir was assessed using heavy metals bioaccumulation in water, gills and liver samples of C. gariepinus between July and December, 2019. Heavy metals analyses were carried out using microwave plasma atomic spectroscopy (MP-AES). Water and fish were sampled fortnightly from the three sites coded as upstream (A), midstream (B) and downstream (C) between 7:00 – 7:30am for period of six months. The results revealed that heavy metal concentrations in water followed the order: Cr (2.15mg/L)>Cu (1.40mg/L) > Pb (0.89mg/L)> Cd (0.68mg/L). Bioaccumulation Factor (BAF) of heavy metal concentration in water decreased in the order of Cr > Pb > Cu >Cd. In the fish organs, gills had the highest value of Cr, followed by Pb, Cu and Cd recorded the lowest. The BAF in liver tissues decreased in the order of Cu > Pb > Cr >Cd. BAF for Cu was highest in liver tissue (2.90) while the lowest was obtained in the gills (1.04). Lead (Pb) had its highest value in liver (2.16) and the lowest value (1.33) was obtained in the gill. BAF in Cr had its highest value of 2.15 in water and the lowest was obtained in the gills. Heavy metals bioaccumulation differed significantly (p<0.05) between the sampling sites and seasons with the exception of cadmium which did not differed significantly (p>0.05). It can be deduced that heavy metals bioaccumulation in the fish tissue is attributed to the influx of chemicals into the reservoir as a result of agrochemicals input among other anthropogenic activities. It is recommended that indiscriminate release of the xenobiotic compounds should be minimized in order to avert degradation of the reservoir in the long run. Intervention by appropriate authorities to curtail the effects of heavy metals on fish species among other important biota is recommended.