Abstract

Juveniles of Clarias gariepinus were exposed to different concentrations of cadmium chloride for 96 h under laboratory conditions using static bioassays with continuous aeration to determine its mean lethal concentration (LC₅₀), biochemical alterations, bioaccumulation and histological pattern in a sub-lethal toxicity test. The median lethal concentration (LC₅₀) at the end of the acute toxicity was 120.2 mgL^-1. Also the toxicant led to significant (P<0.05) changes in histotopathological parameters in the kidney, liver, gills and muscle as the toxicant concentration increased. The severity of these conditions was directly proportional to the toxicant concentration. Also, the biochemical studies showed that activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) ranged from (0.115 ± 0.15 to 1.634 ± 0.28) µmol/min/mg protein, (2.354 ± 0.45 to 7.734 ± 0.08) µmol/min/mg protein and (0.028 ± 0.05 to 0.21 ± 0.16) µmol/min/mg protein respectively. These values increased significantly (p < 0.05) with increase in concentration of cadmium chloride. The trend of bioaccumulation of cadmium in the tissues of the test organisms differs significantly (p<0.05) and it followed the order, kidney > liver > gill > muscle. The study concluded that cadmium is a potent pollutant that can cause severe damage in fish and hence man the final consumer.

Key words: Clarias gariepinus, biochemical alterations, bioaccumulation, static bioassays, histopathology.