魚類に対する環境汚染化学物質の蓄積並びに影響の淡水と海水における相違(第1報)クロルデン及びペンタクロルフェノールの海水馴化ティラピアによる検討

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.