The acute toxicity of copper to blue tilapia in dilutions of settled pond water

Blue tilapia fingerlings ( Oreochromis aureus) were exposed to copper (Cu) in a series of static toxicity tests. The water used in this study was composed of settled pond water or settled pond water diluted with deionized water. Estimates of mean 96-h LC50 values (median lethal concentration) were 43.06, 6.61, 0.69 and 0.18 mg/l Cu as copper sulfate) in waters having total alkalinities of 225, 112, 57 and 16 mg/l CaCO 3, respectively. These data demonstrate the typical acute toxicity response of Cu, in which toxicity to tilapia increases as pH, total alkalinity and total hardness decrease. The results indicate that blue tilapia are relatively tolerant to Cu when compared to other species and that copper sulfate treatments in low-alkalinity waters may be detrimental to the health of blue tilapia.