Other coral reefs also lie near the mouth of the bay. About 1,225 types of coral have been identified near Okinoshima Island off Tateyama City. Coral moves up into Tokyo Bay from the south, swept along by the warm Kuroshio Current. Other creatures come too, like tropical fish and a surprisingly wide variety of life from tropical and subtropical seas, including aoigai and umihotaru . Even a number of varieties of anemone fish, which live symbiotically with sea anemones, can be seen throughout the year.
Tropical fish ride the tidal currents, pushing further north into the bay.
They even swim north of the strait between Futtsu Point in Chiba Prefecture and Kannonzaki in Kanagawa Prefecture - in other words, they end up deep inside the bay. During the summer, tropical fish can be spotted on Sanban Shoal at the inner arc of the bay. Actually, the bay is teeming with life, much more than you might think. The high rate is probably due to the abundance of plankton on which they feed, and the quiet water that allows the sweetfish to maintain concentrated communities. In recent years, sweetfish have even been seen swimming upstream in the Kanda, a river that has been developed as much as any in the metropolis.