Rearing of fertilized egg

4.2.1 Collection and rearing of fertilized eggs, larvae and fry The collection of floating eggs,
larvae, and fry of fishes spawning
in rivers and inundated areas (viz.,
the major carps) is an age-old
practice in India and China. A large
number of funnel shaped nets are operated along gently sloping
banks of rivers in the path of the
drifting eggs or larvae. These nets
are constantly watched and the
eggs or larvae collecting in the tail
piece emptied periodically. The seeds thus collected are placed in
small earthen pits with or without
continuous water flow or in cloth
enclosures (hapas) fixed in the river itself for temporary holding
and conditioning before transport.
In the case of eggs, they are
allowed to hatch in these pits or
hapas and the larvae allowed to grow for a few days. The larvae are
then transported to nursery ponds.
Similarly, the fry collected from the
rivers in special fry collection nets
are also transported to nursery
ponds for further rearing. The fingerlings raised are used for
stocking fish ponds. The artificial intervention in this
procedure consists of
(1) collection
of eggs, larvae or fry; (2) their
protection from natural enemies
and unfavourable environmental
factors;
(3) raising the larvae up to the fingerling stage, and
(4)
distributing them for stocking in
different water bodies. This technology of river fish seed
collection can be easily adopted in
other parts of the world where
useful river spawning fishes are
available in adequate number.
However, this technology has several dis advantages. The
collection is generally not pure, but
a mixture of several species some
of which may be predators or of
undesirable type. It is not easy to
separate the various species, particularly in the early stages.
However, some techniques have
been developed both in India and
in China to segregate desirable
from undesirable seed. These are
successful only to a limited extent, and one has to wait until the larvae
develop into fry with
distinguishable characteristics for
proper identification. The collection
technology is labour-intensive and
requires special skill in handling and transport. Another
disadvantage is that the brood
stock is unknown and there is
hardly any possibility of improving
the stock. Many authors do not consider this
techniques as artificial
propagation, although the helpful
artificial interventions into the life
cycle of the fish are obvious.

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