| Little
is known about a river dolphin's natural history.
However, several species are in danger of extinction.
Threats to river dolphin populations include pollution,
subsistence hunting, industrial development, dam
construction, riverbank deforestation, over fishing,
and incidental capture in commercial fisheries.
Why
is the baiji endangered? Varying water levels
in the Yangtze River due to industrial development
have limited available habitat. Over fishing has
decreased the baiji's food supply. Pollution harms
both the dolphins and their prey. Baiji may be
injured or killed by explosions during construction,
and by boat propellers.
A
number of baiji are caught and killed by illegal
fishing devices called rolling hooks. These long,
braided lines with numerous sharp hooks are meant
to catch fishes. However, baiji also may become
ensnared in the mass of hooks. Others become entangled
in stake net traps.
The
baiji has been protected by China since 1975.
Chinese biologists began devising a protection
strategy in 1986. By establishing reserve sites
along the Yangtze River, scientists are hopeful
that the species can be saved.
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