Koi spawning behaviour occurs once per year, usually over a period of a few days. When the conditions are right, water temperature, day length etc the spawning begins (here in Ontario, usually between Late May to late June). Often before the actually day of spawning, you will notice one or more males showing more interest in a female, closely following her around the pond for a day or two. Spawning usually begins early in the morning with the males aggressively chasing and nudging the female(s) around the shallows or edges of the pond. Like most fish, koi are egg layers, and once the female sheds the eggs they they will stick to whatever they come in contact with. A large mature female can produce up to 400,000 eggs, and as the eggs are shed, they are immediately fertilized by the males that are following her. Koi (and goldfish) prefer to deposit their eggs in vegetation normally found in the shallow water of ponds. By providing plenty of plants like hornwort, water hyacinths or water lettuce or even artificial spawning mops or ropes, you can provide an ideal breeding habitat for them.
The video below shows koi that have been spawning in the shallow stream at the base of a waterfall. Most of the eggs deposited were deposited in the water cress. Notice the foam at the bottom of the waterfall, that is a sure sign that fish have been spawning in the pond.
[column col=”1/2″]DAY 1
The opaque sphere on the right is a koi egg one day after spawning. Eggs will stick to whatever they land on once released by the female, in this case on root of a water hyacinth.[/column][column col=”1/2″]
[column col=”1/2″]DAY 4
Depending on water temperature, the eggs usually hatch in 3 – 5 days. the juveniles are about 7 mm long and will feed from their yolk sac for few days.
[column col=”1/2″]DAY 9
[column col=”1/2″]DAY 11
[column col=”1/2″]DAY 29
The opaque spheres on the right are koi eggs one day after spawning. Eggs will stick to whatever they land on once released by the female. In this picture, they are attached to the roots of water hyacinths.
Depending on water temperature, the eggs usually hatch in 3 – 5 days. When they hatch, the juveniles are about 7 mm long and will feed from their yolk sac for few days until they are more developed and can eat food.
The fish are beginning to feed on infusoria (microscopic creatures) found in the water.
The fish are now capable of feeding on larger prey, such as small Daphnia. These koi are feeding on finely ground flake food. You can see the swim bladder and digestive tract as their bodies are still transparent with a yellow colour.
The fish are growing fast and are now starting to really look like little koi. At this age they start to show their colour