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The green mitten crab, Eriocheir rectus, is only
distributed in Taiwan and a new name will probably be used .
It mainly inhabits the rivers and streams of eastern
Taiwan but is most popular from the Nanao Stream. The
sea-ward reproductive migration is in the autum-winter
period for the other Eriocheir species but it is between
spring and summer for E. rectus. It has high commercial
value and is also an important subject for academic studies.
From september 1991 to september 1992, the materials were
caugth at three sampling sites (midstream, downstream and
estuary) and some ecological factors were also measured. The
results appeared the sea-ward migration in spring was the
reproductive period of this crab. Furthermore, summer was
the spawnig, natual dead and megalopa up-stream migration
periods. The monthly rain fall, water temperature and grain
size of the substratum on the river bottom were the three
most important environmental factors affecting the
distribution of the crab in the stream. The life cycle of
this crab population were mainly composed of 2 years. Only a
few of them belonged to the 1 year or 3 years. Relative
growth estimates the size of first maturity for males and
females to be 45mm and 35mm respectively. Females have an
average of 174,400 eggs. Of the 750 specimens examined, no
Paragonimus parasites were found at all. At last, the
suggestions about its conservation were also described.
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