As spring grows older the weather in Niigata changes dramatically, the harsh winters snow have melted and disappeared leaving mud ponds filled with fresh pure water.  By early May the daytime temperatures can reach the mid 20’s Celsius.

With Koi released to mud ponds the breeders’ minds turn to spawning, the creation of a new generation of Nishikigoi.

In this article we’ll look at what the spawning process entails.

It is said that when the Weigela flower blooms then it is the time to start spawning.

Weigela photographed in Mushigame Village 16th May 2008

Weigela photographed in Mushigame Village 16th May 2008

There are 2 methods by which spawning (sanran in Japanese) is carried out, naturally, or artificially.

Natural spawning simply involves placing sexually mature males (3 years+) and females (4 years+) together and letting them do what comes naturally, although of course there is slightly more to it than that.


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Artificial spawning involves the eggs and sperm being stripped from the female and male respectively before being mixed together by hand.

Both processes essentially start the same with the breeder placing males and females together early in the morning before the evening which they hope them to spawn.  In Japan the female will produce just one batch of eggs each year, and at this time of year they are ready to release them as part of their natural annual cycle.  Males on the other hand can produce sperm any time, and can be used on multiple occasions.

Exactly what happens throughout the entire spawning process varies from breeder to breeder.

Some breeders choose to carry out their spawning in concrete ponds, others prefer to use holding ‘nets’ placed in mud ponds.

Maruju Koi Farm place the male and female parents in the show pools prior to artificial spawning

Maruju Koi Farm place the male and female parents in the show pools prior to artificial spawning

Isa Koi farm parents held in a net in a mud pond prior to artificial spawning

Isa Koi farm parents held in a net in a mud pond prior to artificial spawning

Vinyl sheets are suspended in the concrete ponds at Marudo Koi Farm

Vinyl sheets are suspended in the concrete ponds at Marudo Koi Farm

If the breeder is to carry out natural spawning 1 female will be placed with 2 or maybe 3 males along with spawning material onto which the eggs will be laid.  Traditionally this would be the soft leaves of the Japanese Cedar trees that abound around the mountains and, whilst still used by some, most use artificial nylon spawning ropes.  As dusk falls the male or males would likely start showing an interest in the female, pursuing her around the holding net, gently rubbing their faces and pectoral fins against her.  The males have small lumps on their gill covers and pectoral fins called oiboshi.  They use these to signify to the female that they are ready to spawn.  All being well, by daybreak the spawning material will be coated with fertilised eggs.

Koi in mud pond spawning set up with Japanese Cedar branches

Koi in mud pond spawning set up with Japanese Cedar branches

Kohaku parent set spawning naturally at Torazo inside a fine mesh net in a concrete pond.  Torazo uses a combination of natural and artificial spawning depending on the importance of the parent set.  More important parents will be spawned artificially.

Kohaku parent set spawning naturally at Torazo inside a fine mesh net in a concrete pond. Torazo uses a combination of natural and artificial spawning depending on the importance of the parent set. More important parents will be spawned artificially.

Kohaku parent set spawning naturally at Torazo inside a fine mesh net in a concrete pond.  Torazo uses a combination of natural and artificial spawning depending on the importance of the parent set.  More important parents will be spawned artificially.

Kohaku parent set spawning naturally at Torazo inside a fine mesh net in a concrete pond. Torazo uses a combination of natural and artificial spawning depending on the importance of the parent set. More important parents will be spawned artificially.

If the breeder is going to do artificial spawning then many more may be placed together (see picture above), both males and females, indeed the more there are the quicker things are likely to get going with regards to the female releasing her eggs.  Throughout the course of the evening the Koi must be monitored carefully for as soon as the female starts to release her eggs she needs to be isolated from the males.  Having been separated the female is allowed to rest for 1 hour so that the eggs ‘loosen’ to enable them to be stripped more easily.


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The Torazo parent Koi 'Kokugyo Sanke' is pursued by males prior to artificial spawning

The Torazo parent Koi ‘Kokugyo Sanke’ is pursued by males prior to artificial spawning

After she has started to release eggs the males are placed outside the net

After she has started to release eggs the males are placed outside the net

After 1 hour the female is anaethetised and then turned upside down and carefully wrapped in a towel to secure her.  It is vital that her vent area is clean and dry before the removal of the eggs commences, if the eggs come into contact with water then they will harden, preventing fertilisation. Upon turning her the right way up the eggs will freely flow from her vent with a little pressure applied to the abdomen.  Care is taken to ensure all eggs are removed, any left could cause future problems.  A large mature female will produce hundreds of thousands of eggs.  The female’s job is complete for the season and she is returned to the water to recover.

Masaru Saito of Shintaro Koi Farm washes the underside of the female Koi prior to stripping eggs

Masaru Saito of Shintaro Koi Farm washes the underside of the female Koi prior to stripping eggs

The Koi is carefully wrapped in a towel so she can be held securely and safely

The Koi is carefully wrapped in a towel so she can be held securely and safely

When she is turned back upright the eggs flow freely from the vent

When she is turned back upright the eggs flow freely from the vent

In turn the male, or males, that are to be paired with the female are also anaethetised.  Again the vent area is thoroughly dried to ensure no water is mixed in with the sperm when it i extracted.  Gentle pressure is applied either side of the body to the area between the pelvic fins and vent with thumb and forefinger to encourage a flow of sperm which can be sucked up from the vent opening with a pipette or syringe.

When she is turned back upright the eggs flow freely from the vent

When she is turned back upright the eggs flow freely from the vent

With sufficient sperm extracted for the volume of eggs the male can again be returned to the water.

The final, and most critical stage of the process, is to mix the sperm and eggs.  The sperm is mixed with Ringer’s solution – a liquid with the chemical make of the internal fluids of the Koi – and in turn mixed with the eggs and they become fertilised.

The sticky eggs are then distributed evenly across a frame of nylon spawning ropes to which the eggs instantly adhere.  This stage is repeated on both sides of the framework, and onto further frames until the eggs are all been used.

eggs are distributed across the frame of spawning ropes

eggs are distributed across the frame of spawning ropes

eggs clearly seen sticking to the fine nylons hairs of the spawning rope

eggs clearly seen sticking to the fine nylons hairs of the spawning rope

 


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By the following morning, whether they have spawned the Koi naturally or artificially, they will hope for the same, lots of fertilised eggs.  Exactly how they handle them thereafter will vary from breeder to breeder.

Sometimes the breeder will treat the eggs with malachite green to prevent them from fungal infection.

Fertilised eggs being treated with malachite green at Marudo Koi Farm

Fertilised eggs being treated with malachite green at Marudo Koi Farm

If the spawning is of Showa, Shiro Utsuri or other black based varieties they will hatch the eggs and grow the fry for 5 days or so.  Then they can conduct kuroko selection, the process of keeping only the black fry.  The kuroko (the black fry will then be released to the mud pond.

For other varieties breeders may prefer to hatch them inside the concrete ponds, or indeed place the eggs into mud ponds to hatch, adsorb the egg sac, become free swimming and then release them.

Fertilised eggs at Torazo waiting to hatch.  Once the fry are free swimming they will be transferred to mud ponds to grow

Fertilised eggs at Torazo waiting to hatch. Once the fry are free swimming they will be transferred to mud ponds to grow

At Shintaro Koi Farm, following treatment, the eggs are placed inside spawning nets in a mud pond.

At Shintaro Koi Farm, following treatment, the eggs are placed inside spawning nets in a mud pond

When the fry have successfully hatched the side of the net is dropped allowing them to swim freely into the pond

When the fry have successfully hatched the side of the net is dropped allowing them to swim freely into the pond

At Maruju Koi Farm the fertilised eggs are placed into nets secured in mud ponds until they hatch and become free swimming

At Maruju Koi Farm the fertilised eggs are placed into nets secured in mud ponds until they hatch and become free swimming

Here Shigeo Tanaka carefully measures the quantity of fry from the spawning before they are moved to growing ponds

Here Shigeo Tanaka carefully measures the quantity of fry from the spawning before they are moved to growing ponds

Tiny 1 week old fry being transferred to the mud pond in which they will grow

Tiny 1 week old fry being transferred to the mud pond in which they will grow

 

I hope this article has given you an insight into the process that in undertaken in spawning Koi.  Like so many aspects of raising Koi in Japan things vary widely from breeder to breeder however, all with the same goal.


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