Abstract
Comparative acute toxicity tests were carried out with three heavy metals viz. cadmium, copper and
lead on giant prawn (Macrobrachium rosenbergii) and tiger prawn (Penaeus monodon) post larvae.
Lethal concentrations at which 50% of the shrimp died (LC50) at 96 h were 3.23 mg/l Cd, 3.02 mg/l Cu
and 10.0 mg/l Pb for M. rosenbergii; 2.91 mg/l Cd, 2.16 mg/l Cu and 7.28 mg/l Pb for P. monodon. The
metals showed toxicities in the order Cu>Cd>Pb. The LC50 values recorded for M. rosenbergii were
higher than the values recorded for P. monodon, hence the specific metals were more toxic to P.
monodon than M. rosenbergii. The safe concentrations for all these metals were also calculated. This
study has produced LC50 values that may be useful in screening potentially toxic substances in our
waters.
Key words: Toxicity, heavy metals, shrimp, post larvae.
