Baby Koi


David Demarest

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Back towards the end of March/early April, we had—what seemed to be—a little miracle fish added to our pond. We had never seen any eggs or any other little fish swimming around, but one day I saw this little off-white koi with a big orange circle on his back, swimming very tentatively, close to one of the patches of grass that we have in the pond. Prior to his appearance, and even for a brief time after, we would come outside and see one of our adult koi would wedge itself deep into the same patch of grass.

Is it rare for only one Koi to survive from the brood? Part of me feels bad that we didn’t see the other babies, but maybe they were all eaten as eggs? And on the other hand, letting nature take its course isn’t the worst thing I’ve done this year haha.

All we knew was that one of the koi (the white one with black and orange spots) was hanging out deep in the pond grass for an extended period of time, and sometimes the other two would hang out close to it. I like to think that it’s a modern family with three parents and one child, not that the other two were waiting to possibly eat the eggs/young. Do Koi eat other Koi’s eggs? We’ve had lots of aquariums and even a previous family of koi and a catfish in the pond, and we tend to point fingers at the catfish when things go wrong. One time we had a nice healthy aquarium with dozens of fish and one day we introduced an albino channel catfish to the mix. Within a week or two, it was just him and the gourami (with a half-eaten tail) left, so even though we love catfish and know they’re and important part of the ecosystem, they’re also our go-to scapegoat. For that same reason, I’m not surprised that the Koi chose to stay close to the patch of grass where the catfish doesn’t live.

Also, is it easy to tell when a Koi is pregnant?

I’ll upload some pictures of the pond and the koi. I’ll also include a link for a Dropbox folder that contains some videos I took for another post.

https://www.dropbox.com/sh/kj8jbguxvfe6is5/AAAUN1RpZcTaknSYbsjCWoV_a?dl=0
 

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Koi don't really get "pregnant". The females produce eggs which get released during spawning and fertilized by the males. Often more than one male gets in on the spawning action. And when you see the millions of eggs that get released, you realize that it's a good thing most get eaten!

You can tell that a female is full of eggs if you know what to look for. I can usually only tell after the fact as the females will be noticeably thinner. The behavior you saw may have been spawning, although it's usually hard to miss as it gets quite... well, violent is one word for it. Lots of splashing and chasing. Basically the eggs are released when the female gets pushed against the rocks or pond side - over and over and over. It can be exhausting for the female especially if she's being chased by more than one male, and she may try to hide to escape the "attention". Spawning can affect water quality, too, and at the very least it will cause the water to be foamy. There's also a characteristic odor - hard to miss. Sometimes spawning lasts for hours, sometimes it's over very quickly. So it is possible to miss if you're gone for a day for example.

One tip on posting videos here - upload to YouTube and then post the link here. Works great!
 
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Hi David. Letting nature take its course is actually the best thing you can do. If there are too many hungry mouths then eggs and baby fish get eaten and if there is room in your pond for more fish somehow the babies survive. I only had one baby make if from my batch from last year and at one time there must of been hundreds of tiny fry.
 

David Demarest

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That makes perfect sense because they were getting pretty frisky and I had never seen behavior like that before. The white one with black and orange spots would be in the grass and the other two (usually one at a time) and they would be thrashing. I can’t say I recognized a smell, but I can try to look out for it if it happens again. Is it a fishy odor? Are the eggs usually visible or do they usually dig a nest into the ground? How many eggs do they usually release and do they all get fertilized? Do most of the eggs get destroyed, eaten, or are they just left unfertilized and deteriorate? If they get eaten, do they tend to get eaten before or after fertilization? Or is it just completely the total indescriminate random side of nature?
 
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The eggs are incredibly sticky - that’s why the female tries to get into the planted areas. She instinctively knows that gives the eggs the best chance. Of being fertilized and hatching. Thousands of eggs get released - literally. And they will stick to any available surface. I rescued one of our females during a spawning this year and got eggs all over my arms, feet and flip flops. I was still picking dried eggs off my shoes a week later! If you know what to look for you will see the eggs - if the fish leave any behind. Mine follow the spawning activity like it’s a breakfast buffet.

As far as how many get fertilized - totally random I’m sure. And the other fish - as well as the female who produced the eggs I imagine - will eat the eggs as fast as they are released. I don’t know at what point they decide the babies are no longer delicious - we’ve seen fry so tiny you can just make them out that the adults leave alone. So they must have standards. Haha!!

Search for koi spawning on YouTube - you’ll find lots of interesting information and know what to watch for!
 

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