Abstract
Seaweed communities have been observed on the eastern shore of Ishikari Bay in a rocky area north of the Ishikari River estuary. Spawning by herring (Clupea pallasi) was confirmed in sea areas in the bay where Phyllospadix iwatensis cluster in the seaweeds vegetation.
The Ishikari River flows into the Ishikari Bay. The river catchment area accounts for one-sixth of Hokkaido's area, and this river is typical of those in Hokkaido. It is thought that the water that flows out from the Ishikari River influences the growth of seaweed vegetation on the eastern shore of Ishikari Bay.
We investigated the seaweed distribution and the water quality on the eastern shore of the bay. Many species of seaweed were found to be inhabiting the Ishikari River estuary, and many perennial seaweeds were found to distribute in those area. Laminaria religiosa, a large annual alga, predominates offshore of the estuary. A relationship was confirmed between seaweed distribution and salinity, and seaweed distribution and nutrient concentration.
