The Toxicity of Zinc and Cadmium to Clarias submaginatus

  • J. A. O. ORONSAYE Department of Fisheries, University of Benin, Benin city, Nigeria
  • N. F. OKOLO Department of Fisheries, University of Benin, Benin city, Nigeria
  • E. E. OBANO Department of Fisheries, University of Benin, Benin city, Nigeria

Abstract

The toxicity of zinc and the influence of cadmium on the toxicity of zinc to Clarias submaginatus was investigated under laboratory conditions. The fish were exposed to Zn concentration of 0.25, 0.5, and 1.0 mg/l used alone or in combination with equal amounts of cadmium used together at 27 ± 20C, in water 45 mg/l hardness expressed as CaCO3 at pH 6.5 in a static system in tests which lasted 200 hours. The median lethal concentration, (LC50), obtained were a 4-, 5- and 10-day LC50 values of 0.76, 0.50 and 0.21 mgZn/l respectively when zinc was used alone. In the mixed solution containing Cd, the 2-, 4-, 5- and 10- day LC50 values were 0.90, 0.42, 0.29 and 0.12mgZn/l respectively. The mixed solutions containing zinc and cadmium were twice as toxic to the fish as solution containing only zinc. Synergism is indicated.

Key words: Clarias submaginatus, zinc, toxicology

Journal of Aquatic Sciences Vol.18(1) 2003: 65-70
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Articles

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eISSN: 0189-8779