The sweet fish (alevin ayu plecoglossus atlivelis) hatch out in the shoals of river and they drift down the river
into coastal zone immediately This study is carried out survey of salinity, water temperature and dissalved oxygen in
the tidal compartment of Niyodo River to understand the environmental characteristics of flow and
water quality in the compartment for the drifting sweet fish.
Niyodo River is ohginated from Mt. Ishizuchi (1,982m) that is the highest mountain in the west of Japan and
running through the Kochi-Plain and into the Tosa Bay. Niyodo River has a length of 124km with 1,560km2
river basin. The maximum discharge is 5480m3
/s, the minimum is 9m3
/s and the annual mean flow is 118m3
In the river mouth, the width is about 1km and the groin had been established at the left side. But the usual flow
is 60m width because sand spit has been developed. It is shallow in river mouth. Riverbed is so irregular where
there is over 10m depth in a part. The tidal range is about 2m at the flood tide and about 0.6m at the neap tide.
In the river mouth, the water level changes with the tide.