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3. Actual Spawning.
The pregnant female shows
her readiness to spawn by exhibiting movements that seem to indicate
an intention to arrange the spawning material into a nest. The
male is attracted to these movements, and tries to force the female
against the wall of the pond. If there are two males in the
pond, they will attempt to sandwich the female between them.
The thrashing and bumping of the males against the pregnant female
causes the latter to release her thousands of eggs into the spawning
material (and into other places as well). The eggs are very
sticky and will adhere to anything they come in contact with.
Simultaneously, the males will release their sperms onto the eggs to
fertilize them. A second cycle of the same ritual may be
employed if the female still needs to discharge some eggs.
This spawning activity (see
Figure 2) can be
very physical, or even violent. Injuries to the female may
happen, especially if the male koi continues to beat her up.
The male should be promptly but very carefully removed from the pond
if this happens. It would be good to leave the female in the
pond to let her recover her strength. Keep her safe by keeping
her properly aerated and preventing her from jumping out of the pond
(some females have been observed to be jumpy after spawning).
Figure 2. Photo
of actual koi spawning
and Incubation of the Eggs.
The eggs, being small and
immobile, are vulnerable to
predation not only by its parents but by pond wildlife as well.
Thus, it is necessary to secure the eggs from predators. If
you used spawning ropes as spawning material, you can easily lift
these from the spawning pond and transfer them to a hatchery (which
can just be a vat or tank) where the eggs can incubate safely.
If you don't have a separate hatchery and intend to let the eggs
hatch in the spawning pond itself, you should transfer the
female carefully to another pond.
The hatchery (if one is used)
where the eggs will be transferred and allowed to hatch must be of
the same temperature as the spawning pond. It must also be
aerated very well with no water disturbance. Filtration of the
hatchery is not required, but adequate oxygenation is certainly a
5. Rearing of the Larvae.
Most of the eggs usually
hatch 4 to 5 days after they are laid.
By the 6th day all of the fertile eggs should have hatched. The
newly hatched larvae will look like a huge army of jerking 'commas'.
The main challenge in rearing the newly hatched larvae is feeding,
which can pollute the water as wastes build up especially since
filtration should not be done at this point. The larvae will
survive on their egg sacs for the first 24 hours. After that,
the larvae must be fed 5 times a day. Do not give dry food to the
to prevent water pollution. Instead, give them live natural
foods such as daphnia and infusoria. The growth of green algae will
also help augment the natural food supply. After a few days
the larvae may be transferred very carefully to a larger growing-out
pond where they should continue to receive live food until 6 weeks
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