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【MANGROVE FOREST】 A vast mangrove forest spreads at the delta where the Yakugachi and Sumiyo
Rivers meet. It boasts of being the second largest in size (71ha) after that of
Iriomote Island, Okinawa Prefecture. Our mangrove forest consists of more than
ten kinds of trees. Mehirugi (Kandelia candel) and Ohirugi (Bruguiera
gymnorrhiza) trees are typical.
Picture 1 shows Mehirugi trees. Their white flowers
bloom around July and the slender, viviparous fruit come to maturity on the
twigs almost after a year, reaching the length of 20 to 40 centimeters. Then
they drop to the muddy sand. Some stick in the mud and grow there. Some are
carried off to other places by the waves. If they are lucky, they will germinate
and grow there.
Picture 2 shows Ohirugi trees that form a canopy,
overhanging both banks of the stream. At high tide, you can enjoy canoeing
through the tunnel of Ohirugi trees.
The mangrove swamp is inhabited by various small
creatures. At ebb tide, Minami-Kometsukigani crabs (Southern-Japanese
sand-bubbler crabs/Picture 3) are in countless numbers on the tidal flat. Their
uniqueness is that they walk forward, not sideways like almost all other
crabs. They scoop mud into their mouth and take in only organic matter,
filtering out impurities. If you would like to watch them, you will need a pair
of binoculars or a telescope, because they easily frighten and bury
themselves into the mud very quickly.
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