Koi Breeding Behavior | Koi Spawning Behavior - Breeding Koi Can Be Tricky

I recently received an email from a gentleman by the name of Julio who wanted some further information regarding breeding his Koi and other pond fish.

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"Hi Sean:

I have been reading your advice for some time now and had good results in keeping my 500 gal pond free from algae and debris.

Now I have a question of another kind.

How do I go about reproducing my fish? I have some 20 koi and comet gold fish, mostly koi. from 12+ inches long to 5 inches long. The size determined by the date of acquisition.

My pond is concrete, square edged walls and bottom with pebbles in most of the bottom. Some aquatic plants in plastic containers, mostly water lilies, a tetra biofilter and tetra 500gph pump.

I tried planting hydrilla, easily acquired locally intending it to oxygenate the pond and , as it is planted at the bottom, serve for the eggs to adhere to its leaves and at the same time, serve as hiding place for goblins (baby fish). The problem is that the fish eat the hydrilla.

I do want the fish to reproduce!

I could use floating water hyacinths whose long roots could serve my purpose but for the problem of mosquitoes breeding at the bottom of their leaves.

What do you advise???"

My response to Julio!

"Hi Julio

It sounds like you have a great set up and good conditions for your Koi and other fish to breed. One thing that does bother me however are the pebbles at the bottom of the pond; these encourage areas for food and pond sludge to become trapped and generally encourage the build up of unwanted bacteria. The pebbles also make it harder to vacuum up pond sludge and other organic debris.

Anyway that isn't what you are asking. So here goes...

This might sound obvious but you do have a mixture of male and females I hope! Judging by the size of the Koi I would assume that they are mature enough to breed.

First things first I would like to point out that I am by no means an expert when it comes to breeding Koi but am aware of the basics, of koi breeding behavior and koi spawning behavior. I will point these out for you in the following sequence of paragraphs.

Koi Breeding Behavior ... Breeding Koi is stressful to the female Koi

The breeding behavior of koi isn't romantic to say the least. Far from being polite suitors male Koi are quite aggressive in their breeding behavior and will readily charge into and bash the females in order that they will release their eggs.

This aspect of koi spawning behavior often leaves many female Koi injured and extremely exhausted as a result of the physical abuse they have had to endure from the aggressive males. This however is the way it is meant to be and this aspect of Koi breeding behavior has much in common with their wild carp cousins.

Koi Spawning Behavior ... When and How Do Koi Spawn?

It is a bit strange that your Koi and other fish haven't already spawned in previous years given the size of the fish! Koi carp, a descendant of wild carp have the same biological clock as their less colourful, wild cousins and spawn when conditions are ideal for their young to survive i.e. early summer or late spring when there is an abundance of available food (insects etc).

Koi spawn as a result of the water temperature and also the number of day light hours (photo period). The number of daylight hours is fairly consistent year in and year out unlike the water temperature, which will vary from year to year. As a result different parts of the UK (where I live) will see Koi spawn at different times; if they spawn at all that is.

With the water temperature at around 20 Celsius (68 F) the females are nearly ready to release their eggs. But not quite. As the days get longer the eggs within the females mature. The final requirement for the eggs to be released is the presence of male koi carp.

The professionals have a major advantage over you in that they can keep the male koi and female koi apart to prevent spontaneous spawning from taking place. Unfortunately in your 500 gallon pond, you are likely to experience (or even miss) a spontaneous flock spawn.

Koi Spawning Behavior .... Why Is a Flock Spawn Bad?

There are several reasons why a flock spawn is bad and ultimately limits the opportunity for a plentiful supply of fry to be produced...

It often results in physical damage to female Koi, as mentioned earlier when discussing aggressive male koi breeding behavior
Reduction in fertility rates - A females release eggs there is approximately a 30 second window in which male sperm need to find a suitable egg to fertilize. As the eggs swell, due to them absorbing water the micropyle (small duct) through which the sperm will fuse with the female genetic material will closes.
The mad orgy impacts upon the quality of the fry produced. Stronger, healthier males with good blood lines have the same opportunity to breed with the females as much weaker, inferior koi. This results in a weakening of the blood line. It is natures way however.

The reason Why Your Koi Are Not Spawning

A pond environment doesn't offer the ideal opportunity for koi to breed as you have to accept many of the environmental conditions. There are however things you can do to increase your chances of spawning taking place, particularly in the colder northern counties of the UK.

Autumn-Winter. Koi carp have been shown to spawn more reliably the following season if they have endured a at least a 4 week cold spell i.e. pond temperatures below 4 Celsius (39F). This in effect resets their biological clock (body clock) back to zero.
Spring-Summer. Now that they have been through a 4 week cold period, which reset their biological clock to zero it is time to heat the pond from mid February (Northern hemisphere). Aim to achieve a minimum of 15 Celsius (59 F) each day for 1000 degree days. NB as the water temperature is slowly raised and held at 15 Celsius your koi are subjected to a lengthening photoperiod. Therefore 3 days at 15 Celsius equals 45 degree days. This continues until 1000 degree days is reached. Once achieved, koi are likely to spawn. Give them a final helping hand by bringing your pond temperature up to 23 Degrees C.

Spawning Time Has Arrived

Once the 1000 degree days has been reached the females will be ready to release their eggs and now you can add spawning media such as soft rope or woollen mops. The Koi will deposit their eggs against the spawning material. You will need to remove the spawning material to prevent adult Koi from eating the eggs and subsequent fry.

Raising The Koi fry

With an unplanned spawn i.e. what happens in your pond there will more than likely be sufficient notice in which you can prepare to keep the eggs from being eaten. For this reason from thousands of eggs there will only be a relatively small amount of fry that survive to become small Koi (fingerlings).

So Julio if you plan on breeding your koi and other pond fish then you need to supply a safe environment for them to hatch and grow in; an almost impossible job in a natural pond environment.

Strangely enough when it comes to the survival of Koi fry the best opportunity is afforded by unfiltered natural ponds with a plentiful supply of algae and zoo plankton.

Hopefully you will now be a bit more aware of what you need to do and also be a bit more aware of the limitations of attempting to breed your Koi and other fish in a pond environment. I'm not sure exactly where you live but if you live somewhere cold it will be worth investing in a Pond Heater during the cold winter months.

Regards"

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