Fisheries at Shimonoseki area and waste management

Koya river estuary at Shimonoseki city had brought good income to seaweed farmers by seaweed and short-necked clam. But successive withdrawal from seaweed aqua-culture continues in recent 20 years, and harvest of short-necked clam decreases quickly The decline is caused by change of aquaenvironment. especially quantity and quality of river water Moreover, waste management had been m operation from 1995 at reclaimed land beside the mouth of Kanda river The outfall discharge from the waste management is faced to sea and it directly flow into the beach at ebb tide Discharge decrease of Koya river between 1985 and 1997 is illustrated by the comparison of two satellite images taken by Landsat TM The sea water exchange of this estuary is very low and river water contains lol of fine suspended sediment by the actual site observation and hearing from farmers