Whether you are a Koi-breeder, a hobbyist trying to breed or a hobbyist whose Koi just breed by themselves, there are a few important factors to keep in mind during the spawning season.
In South Africa, spawning generally occurs from mid-spring to late summer September to November in the early morning hours when the water is a warm +20 ºC. The Japanese say the best spawning time is during the full moon phase.
Is it a boy or a girl?
To determine the sex of a young Koi is no easy task, but as they grow older, it will be a lot simpler. Look out for the following to determine the Koi's sex:
Females tend to have rounder bodies and pectoral fins. When female Koi are ready to spawn, they look fuller and heavier than normal.The fins are also a bit smaller.
Males are more slender and sleek, with larger fins.
· You can physically examine the Koi by very gently rubbing your thumb and forefinger along the lower abdomen wall. Be sure not to injure the fish. A male will secrete semen.
· Another simple way in which to determine the sex of your Koi is to watching them during the spawning season. The male will be the more aggressive fish, chasing the female.
You will immediately know your Koi have spawned when there is a lot of bubbles or foam on the water surface and a strong smell of ammonia. It is important to be aware of these indicators as, after spawning has taken place, a high level of ammonia will be present in the water and you will need to test it to ascertain whether the level is acceptable. If it is too high and it is not corrected, one can end up with fatalities. (The simplest way in which to correct the ammonia level is a water change, but be careful when doing so or you could have fatalities.)
Selecting the breeding Koi
It is best to wait until your female Koi is at least four years old. From the age of five, they will produce larger more fertile eggs that will result in stronger fry. Females are sometimes able to spawn in the beginning of the season and then again a few months later. Breeding at a young age may cause the parent Koi to lose its colour(s) and patterns.
Your male Koi will be ready for spawning from the age of two years. When sexually ready, small whitish tubercles or nodules will develop on the pectoral fins and gill plates leaving those areas feeling rough. The younger fish can be used every two weeks, but for older males allow greater time periods for maximum fertility potential. Remember the male is more dominant in the gene pool.
How to induce spawning?
If you allow a natural spawn in your pond, the other fish will eat your your eggs, it puts additional stress on the females, and your offspring will be of bad quality due to the free for all condition. It is just not worth it to spawn in your pond, and you can create bad bacteria due to pond filled with eggs.
If you wish to spawn and raise the fry, do it in a controlled manner.
Select your female in the early spring and place her in a separate pond when you see that she is bloated with eggs. Put a net over the pond to prevent her from jumping out.
Ensure a 1000 degree Celsius day which means that the female must be subjected to at least 15 degrees Celsius water for a period of three days(15 x 24 x 3= 1080).
After you have reached this "1000 degree day", add two chosen males to the pond, add spawning material, and increase the temperature to 22 degree Celsius.
As soon as they have spawned, take them out to prevent them from eating the eggs.
Keep the temperature at at least 20 degree Celsius to help the fry to hatch.
Add malachite green to the water to prevent a fungus that will much on the eggs.
Cover the pond with a net to keep out predators.
Add green water filled with microscopic zooplankton to your pond to create a perfect environment for the fry to grow and add some dafnia filled water when they hatch, alternatively, remove them to a natural pond with a lot of green water and natural food.
The ideal spawning environment
Do not select more than three sexually ready males per female full of eggs. When the female is ready to spawn, she will display
"nesting movements" although Koi do not normally nest. Place them in a separate, well-aerated Koi pond with the spawning media suspended from the walls of the pond onto which the female can deposit her semi-adhesive eggs.
Artificial grasses, natural plants, vegetable sacking and shade cloth torn into strips will act as spawning material.
The spawning process
Do not use your show-quality Koi for breeding if you are inexperienced as the spawning process is quite violent when the male aggressively chases the female so that she can release the eggs for fertilisation.
During spawning, the male follows the female and forces or bumps her against the walls of the pond. He may push her with his mouth to force the eggs out. If two to three males are in the pond, they will sandwich her between them and simultaneously fertilise the expelled eggs.
Both Koi can be damaged and end up with bruises, cuts and torn fins, or die. This process is especially stressful to the female and you should cover the breeding pond with a net to prevent her from jumping out.
This process could take four to six hours and the breeding pond will take on a cloudy appearance with a distinct smell.
The female releases between 100 000 to 500 000 eggs before "resting" with her head pointing downwards when done. Now you must move her to another pond to regain her strength and beware that she will still tend to jump out of the water.
At the same time, return the males to their main pond or they will eat the eggs.
Caring for the fry
A 35 percent water change is in order, but be wary of the eggs that are attached to the spawning media. If you are removing the fertilised eggs from the pond, take care not to let them out of the water for too long. Place the eggs in a well-aerated tank no filtration is necessary at this stage, but you will need to treat the water. Your dealer will advise on required medication.
40 hours: the bodies of the fry have formed. You will notice two black dots the eyes.
Five to seven days: the fry break out of their eggshells. They usually are transparent and cannot swim at this stage. They use the sticky pad on their heads to attach to the side of the pond or the spawning media. Cover the pond with fine netting they are easy prey for insects and dragon fly larvae will destroy your harvest. The frys primary food sources for about 24 hours are the yolk sacs that hang from their bellies. Thereafter you will have to feed them.
Week one to two: The menu must include hard-boiled chicken egg yolk placed in a stocking, daphnia and brine shrimp larvae, as well as crushed Koi pellets. (The daphnia and brine shrimps give the fry a better chance of survival, however, they may survive without being fed if your pond is not immaculately clean.)
Week three: the fry will be around five millimetres long and should be showing some colour (usually yellow or white).
Week six: start culling the Koi with deformities (those with no fins, deformed mouths, no or only one colour unless you are breeding ogons, etc.) If you cannot cull, you should not be breeding as it is very necessary. You have to limit your stock to the benefit of the good quality fish.