Acute toxicity of selected heavy metals to Oreochromis mossambicus fry and fingerlings

Abstract

Acute toxicity of copper, lead and iron to tilapia Oreochromis mossambicus fry and fingerlings was tested using 24 h to 96 h static non-renewal toxicity tests. Three methods, probit analysis, Spearman–Karber and a linear regression model, were used to calculate LC₅₀ concentrations. For all three heavy metals, the LC₅₀ concentrations were higher for fingerlings than for fry. Copper was more toxic than lead and iron to both life stages. The species sensitivity distributions of O. mossambicus, as well as those of freshwater fish species from the ECOTOX database and literature, were closely predicted by the models for all three metals. The sensitivity of O. mossambicus to copper, iron and lead varied significantly. The early life stages of Oreochromis mossambicus were less sensitive to copper and lead than most freshwater fish species. The HC₅ concentrations that can be used as guidelines to protect 95% of freshwater fish species in similar environments to O. mossambicus were determined as being <0.001, <0.17 and <0.96 mg l^–1 for copper, lead and iron, respectively. Although there are limited data on heavy metals, the toxicity data generated in this study can be applied in risk assessments for local freshwater species in the rivers of Limpopo province.

Keywords:

• copper
• freshwater
• iron
• LC₅₀
• lead
• pollution
• river
• SSD