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.