Abstract
Since fishes in fresh-water and seawater are well-known to have different physiological mechanisms for the regulation of their osmotic pressure, the accumulation of environmental, chemical pollutants in fish might differ between fresh-and seawater areas. To see this difference, the intakes of chlordane and pentachlorophenol (PCP) were investigated by utilizing seawater-acclimated tilapia (Tilapia nilotica), an originally fresh-water fish. When tilapia was exposed to 50 ppb chlordane-containing water for 24 h, the amount of chlordane recovered from the several organs and tissues was higher in fresh-water tilapia than in seawater-acclimated. Particularly, hepatic chlordane in fresh-water tilapia was as much as about five-fold higher than in seawater-acclimated. The same tendency was observed when chlordane-containing food was dosed. The intake of PCP was also higher, especially in the liver, in fresh-water tilapia than in seawater-acclimated, when the fishes were exposed to PCP-Na (100 ppb) for 2 and 24 h. An acute toxicity test indicated that the LC50 value of PCP on seawater tilapia was approximately twice that on fresh-water tilapia. These differences between fresh-and seawater fishes in the intake and lethal toxicity of chemicals may give a new viewpoint in the ecological evaluation of chemical pollutants.
