RESUMO
The effect of humic acid on cadmium [Cd] toxicity to Nile tilapia and the impact on fish immunological, hematological changes in Nile tilapia [Oreochromius niloticus] were studied. The fish [120 +/- 10g] were exposed to 10 ppm Cd alone or with 0.2, 0.3 and 0.4 g humic acid /I ppm for 15 and 45 days. Cd exposure reduced significantly [P<0.04] such as erythrocyte count [RBCs], haemoglobin content [Hb], haematocrit value [Hct], mean cell haemoglobin [MCH] and mean cell haemoglobin concentration. These parameters were improved when humic acid was applied with Cd. The values of RBCs, Hb, Hct, MCH and MCHC were increased significantly to be as in the control fish group. Addition of humic acid to Cd contaminated medium considerably reduced metal absorption and accumulation in fish tissues, while it was increased metals in water and feces. Fish exposed to Cd alone accumulates 2.15 and 5.970 mg Cd/g dry weight in liver tissue for 15 and 45 days respectively. Cd reduced significantly to 1.292 and 4.16.; 0.92 and 3.791; and 0.41 and 2.43 mg Cd/g dry weight tissue in fishes exposed to 0.2, 0.3 and 0.4g humic acid /I for 15 ; and 45 days, respectively. Similar trends were observed in gills and musculature