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°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.