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Fish resources in natural water bodies are tending to decrease due
to intensified fishing, the extensive construction of hydropower
plants on rivers, and the pollution of seas and freshwater basins
by indus trial and agricultural wastes. Nowadays only artificial
fish rearing can meet man's requirements in fish products. Fish
breeding is still very young as compared to plant breeding and
animal husbandry. Although fishes have been reared artificially
since ancient times in certain Asian countries, this usually
included the cultivation of embryos and larvae caught in rivers and
lakes. Among the exceptions, only the common carp Cyprinus carpio
and the domesticated variety of the crucian carp, the goldfish
Carassius auratus, which were cultivated in the East, may be
mentioned. Com mon carp breeding began in China about 2000 years
ago but was la ter banned by one of the emperors and started again
only relatively recently. The goldfish has been cultivated for
decorative purposes for about 1000 years. Many remarkable varieties
of the goldfish have been developed in China and later in Japan.
The first improved breeds (German "races") of the common carp known
in Europe appeared after the domestication of the Da nube wild carp
in the seventeenth and eighteenth centuries. Local breeds of the
carp were probably established somewhat later in Chi na, Japan and
Indonesia; even now these breeds have only minor differences as
compared to their ancestor, the Asian wild carp.
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