Uptake of zinc by Pteridium aquilinum (bracken fern) and response of Clarias gariepinus juveniles during chronic and sub lethal exposure.

Zinc is an essential trace element but can be toxic to fish at elevated concentrations. This study was carried out to assess the uptake of zinc by Clarias gariepinus juveniles and Pteridium aquilinum during chronic exposure to sub lethal concentrations. Two experiments were undertaken simultaneously in static renewal bioassays for 28 days.Haematology, histology, zinc accumulation in tissues of C.gariepinus and P. aquilinum were recorded fortnightly. Packed Cell Volume, haemoglobin concentration, Red Blood Cells, White blood cells, Lymphocytes, Neutrophils, Mean Corpuscular Volume, Mean Corpuscular Haemoglobin Concentration and Mean Corpuscular Haemoglobin of C. gariepinus varied with increasing exposure period. RBC, WBC, LYM, and NEUT differed significantly among treatments.