It is
extremely important to develop stable seedling production technologies when
fish are farmed. However, there are many fishes
that do not spawn just by putting them in a tank.
【Examples of eels and fox jacopever】
Seedling
production is the process of making fry for farming. The first stage of
aquaculture begins with collecting and growing natural fry or
gathering parents for spawning, but this cannot be said to be sustainable. Once
a
fry grows to an adult fish
and the eggs are harvested, the seedling production can be sustained by farmed fish alone
without relying on natural resources. In the case of Japanese
eel, fries
are
overfished and endangered because we
cannot gather parent fish in the fields during
the spawning season. It is necessary to make fish raised from fry spawning, but
they do not naturally lay eggs in the aquaculture environment. In addition,
some fish, such as the fox jacopever,
a
kind of a viviparous
fish, requires a
long time to mature, and male
spermatozoids can hardly be produced in the aquaculture environment. It is
believed that the cause is the failure to turn on the switch that produces the
necessary hormones
at each stage from sexual maturation to spawning.
