ACUTE TOXICITY OF METALS MIXTURES FOR FISH, Catla catla, Labeo rohita AND Cirrhina mrigala

Acute toxicity (96-hr LC50 and lethal concentrations) of water-borne metal mixtures viz. iron, zinc, lead, nickel and manganese was investigated in three fish species (Catla catla, Labeo rohita and Cirrhina mrigala) under laboratory conditions at constant pH (7), total hardness (200 mgL(-1)) and water temperature (30 degrees C). All the three fish species showed significantly variable tolerance limits in terms of 96-hr LC50 and lethal concentrations against 19 mixtures of five metals. Amongst 19 mixtures/treatments, the mixture of five metals (Fe+Zn+Pb+Ni+Mn) caused significantly higher toxicity to the fish in terms of 96-hr LC50 and lethal concentrations of 49.18 +/- 11.10 and 79.20 +/- 14.73 mgL(-1), respectively. However, Pb+Mn and Zn+Pb mixture was significantly least toxic to the fish with the mean LC50 and lethal concentrations of 85.42 +/- 10.50 and 134.86 +/- 30.46 mgL(-1), respectively. Regarding overall sensitivity of three fish species, Labeo rohita showed significantly least sensitivity to metal mixtures with a mean LC50 and lethal concentrations of 81.73 +/- 12.73 and 128.80 +/- 19.95 mgL(-1), respectively.