Effect of zinc on the distribution of major cations and anions in <i>Clarias gariepinus</i> from Ebonyi River, Southeast Nigeria

Abstract

A 96 hour bioassay was conducted to evaluate the effect of zinc on the distribution of major cations and anions in the muscle of the catfish Clarias gariepinus sub-adults at 13.88 ppm, 26.75 ppm, 53.5 ppm, 107 ppm and 214 ppm. The 96 h LC₅₀ obtained in this study was 26.62 ppm and threshold value of 20.30 ppm. Statistical analysis of physicochemical parameters showed that dissolved oxygen, carbon (IV) oxide, total alkalinity, temperature and pH did not vary significantly at (P < 0.05) from the control. Mortality increased with increased concentration of zinc sulphate. Quantal response included initial increase in opercula movement, erratic swimming, gasping for air, curvature of body, loss of balance, quietness and finally death. The increase in opercula movement was due to possible inhibition action of the toxicant on respiration as well as possible depletion of A.T.P. which may reduce the energy available for respiration. This depletion could have resulted in exhaustion and ultimately, death. All cations and anions (Mg²⁺, Ca²⁺ Na⁺, K⁺ and Cl^-) showed highest uptake at 214 ppm toxicant (Zn) concentration while the lowest muscular uptake was observed at 13.88 ppm Zn concentration during the 96 hr exposure period, with a threshold concentration of 20.30 ppm. There was however, no total inhibition of ionic uptake (both cations and anions) during the study period.