Fresh and healthy specimens of
Oreochromis niloticus (mean weight 70.5± 1.23 g and mean length, 12.3± 1.5cm) and
Clarias gariepinus (mean weight, 41.8±2.3 g and mean length 13.78 ± 1.2 cm) were exposed to heavy metal lead, ranging in concentration from 10 to 18 mg L
‐1 for
O. niloticus and 20 to 28 mg L
‐1 for
C. gariepinus respectively. The 96 h LC
50 for both the species was computed as 12.45 mg L
‐1 (
O.
niloticus) and 22.65 mg L
‐1 (C.
gariepinus). The cichlid fish was exposed to sublethal concentration of lead (2, 4 and 6 mgL
‐1) and catfish (4, 8 and 12 mgL
‐1). The erythrocytes count, haemoglobin concentration, haematocrit and the value of serum glucose increased significantly (
P < 0.01), whereas leucocytes count, serum protein and serum triglyceride after intoxication declined in both the species with the same pattern but in different quantity. After 96 h of time a significant depletion of muscle and liver glycogen was noted, being greater in muscle (16.7% in
O. niloticus) and in liver (15.9% in
C. gariepinus). The response of fish to lead was dose dependent.
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