抄録
Water quality guidelines have been derived to protect aquatic ecosystems in the regulatory framework of many countries. Direct toxicity assessment（DTA）or whole effluent toxicity（WET）testing has been conducted to estimate the toxicity of complex mixture such as industrial effluents using various bioassays. Most countries adopted acute and/or chronic fish toxicity tests in their regulations. For acute toxicity testing, juvenile or adult fish are normally used, whereas the fish embryo toxicity（FET）test is suggested as the alternative to the acute fish tests in Germany. Although Japanese Ministry of the Environment recently started investigation to introduce the WET system for regulatory purpose, bioassays to be employed are not yet decided. In this paper, sensitivities and practical aspects of fish toxicity tests（FET test and OECD Guidelines 203 and 212）were compared for two fish species, zebrafish（Danio rerio）and Japanese medaka（Oryzias latipes）．Results indicate that O. latipes acute toxicity test was the most appropriate method in practical aspects of regulations. The effect of water hardness on Cu toxicity suggested that the water hardness of effluents should be considered to verify toxicity data and to minimize potential toxicity after dilution of effluents.
