FISH KILL PHENOMENON AND WATER QUALITY IN EUTROPHIC SHALLOW RESERVOIR

Abstract

In Watarase Reservoir, a eutrophic shallow lake, fish kill phenomenon has been occurred especially during spring and summer. In this study, the dominant factor of this fish kill was investigated not only from ecological view point but also from that of water quality and movement. It was shown that the primary production of phytoplankton in this reservoir is high enough to feed fishes whose standing crop is high. Field observation with fish finder indicated that almost fishes exist in deep area near the bed. And it was concluded the sudden fall of dissolved oxygen at night, which is caused by stirring mud with strong wind, is one of the important factor of fish kill.