Koi eat koi.
"They do. Whether you've seen it or not I have. Several people have. many Breeders have as well. Some haven't.
other fish eat koi too. And not just fish.
For carp to be "successful" they need to maintain or increase their population. And actually we from here on out need to refer to "koi" or "carp" as the vessel for carrying the genetic program from one breeding session(birth) into another(propagation).
So one koi needs to get together with one other koi and have 2 offspring capable of breeding two more successful offspring in the next generation( after the first two are dead).
All a koi's DNA needs to do is successfully replicate itself in another koi that continues to do what the first koi did.
A koi's DNA is this huge computer program at least that is how they are viewing it now...I think one day the DNA of an organism will be viewed as more...perhaps as a computer WITH a huge program, and a replicator. THOUGH THAT IS MUCH TOO MUCH FOR THIS DISCUSSION.
So the Computer program has to determine a method for getting "itself" from one generation/spawning of its host (the koi's body) to the next generation/spawning (Another koi body..its offspring). And only two of those programs need to remain active/working/alive at the death of the first DNA host(Both parent koi).
Whether we know it, or the koi knows it...it is built into the computer program....
What is "it"?
"it" is variability in many forms..here i will attempt to put down more of my musings...i will stay as focused as i can be because I do not want to draw attention away from just one aspect of koi behavior. but first let me list a few variables that koi have to ensure one koi reaches adulthood and successfully reproduces into the next generation from ALL the spawning attempted by one koi..NOT one from each spawning just one from all of her spawnings...actually two fish as a male is part of the process.
body shape, fin shape, spawning cues, water depth preferences, timidity, intelligence both hard and soft....Color...Millions of variables.
But now to just one
Spatial Relationship to the bottom surface of a Mud or koi pond by young koi.
Not true fry. but very young koi...let me limit this to fish of an inch and progressing to a few inches in length.
This is NOT going to be about spatial relationship to each other which is a very easy trap to divert the topic to wards.
But Spatial relationship to the surface bottom of the pond is intricate enough. And while other aspects are woven into the topic, the point I am trying to explain is just too intricate unless very narrow parameters are established.
before we go further here is a premise: EVERYTHING a koi does is a result of its DNA. You want to talk this over in person I'll be happy to. Not here.
So let's take a "typical" 100,000 non-egg sack-toting baby koi and look at where they are in a koi pond....
Where are they right after they learn to forage for food?
they are EVERYWHERE.
The computer program given each of them has some variation to it. Just as a [wiki]Kohaku[/wiki] couple will throw Sanke, showa, yamabuki, and ochibas..and tons of really serious junk....the same semi-randomness at the time of fertilization throws different behavior patterns.
The small koi will be throughout the water column, from the surface to the bottom. However there will be discernible concentrations...the two most obvious place to the casual observer is in open water near the surface. Why because small koi need food and the food concentration at the pond's surface is greater than most areas in the pond these koi also are programmed to be reckless in seeking food, and these koi also are programmed to seek warm water which controls their metabolisms and therefore they can "grow faster". ( Let's not discuss why growing faster is better in this thread...sometimes it is sometimes it isn't...you don't know when it isn't ask me in another thread)
The second place casual observers see lots of small koi is in the shallows...the reason again is food... as well as warmth(growth again is the main goal).
And to the casual observer that is pretty much where all the koi are...but a significant number (remember only two out of all the parents' breedings throughout their lives need to become adult koi, so "significant" to the DNA of the parents is 1 offspring. But in a spawn of 100,000 probably .1 - 5% can be found toughing out a life in the deep part of the pond, where it is relatively cold and there is little food.
Now we have three distinct groups of koi concerning how they spatial relate to the bottom of the pond. And unfortunately that isn't how it is. there is tons of gray between the three groups. Individual koi, having individual programs will react to their environments differently and may reorient themselves at anytime... Just one easy to follow example...
the school that has left the bottom behind and is actively feeding in the open water and is growing the fastest has up until now gone unnoticed by the nesting Kingfishers now becomes the object of the Kingfishers' attention and the main source of food for the ir babies. The repeated attacks by the Kingfishers will trigger some of the fry to re-orient with the bottom in deep water, while others with "Harder" wiring will continue to come up and try and maintain their position at the surface.
The same Kingfisher scenario could cause some of the koi that were in the shallows to go deeper and STAY deeper...while others will venture back to the shallows even though they were given equally or more severe stimulation to seek safety.
The opposite could have happened...if the school at the surface would have never suffered predation their presence could have reassured the two populations that orient to the bottom to move with them into richer feeding area at the surface...
But that is all "GRAY" for the discussion...
When a spawning is hatched and the fry become "fish" certain ones will inevitably be programmed to stay deep, others will seek the shallows and the warmth and food there, while others will stay in open water at the surface. not so mush a choice but just as they were given their patterns and colors at the time of fertilization they were given their probable behavior.
The interesting thing I have noticed concerning this orientation to the bottom.
I have noticed that young koi OVERALL will seek the sides and bottom of a pond when first put into a pond where there are koi of the size( 8 -12 inchers) that are capable of eating them. And that young koi pin such a setting will stay next to the bottom or the walls if they perceive a threat (real or imagined).
Now I have placed 15 to 50 new 2 inch koi in several ponds. In the uninhabited ponds the small fish ball up quickly and roam the entire water column..they know they are the top of the food chain.
I also placed about fifteen 1-2 inchers in a situation where the koi i placed them with were hungry and were capable of catching the small koi and they did and all of those small koi were eaten even though they attempted to cluster in the corners and hugged the side of the tank.
And then again the more common scenario i have witnessed (not what is happening because I can not see everything. I feel sure that some of the older koi probably at least spooked some of the small koi into believing they were in danger of being consumed) is where the "new" small koi went to the bottom and sides and then organized into the school that was going to be free-swimming" and then there were those that oriented to the sides of the pond, and others swam to the bottom.
the significance of the orientation is one of safety versus food/warmth/growth..
I have two year old koi that are 2 inches that refuse to leave the bottom of the QT, within that same initial group I have koi that started swimming in the water column and were active at the surface feeding and are now over 15 inches..and there are a variety of koi in between...the "inbetween koi range in just slightly smaller koi than the 15inchers that did at first stay on the bottom but decided to leave the bottom and become aggressive feeders...and then there are others that occasionally make a frantic dash up to grab a pellet and then go back to the safety of the bottom..these are just slightly larger than the smallest that stays at the bottom.
Now back to why this is so important to the DNA of the koi...
The DNA's vehicle is a koi, success is measured by "1"s not thousands. if one koi lives to be able to reproduce then the DNA is successful.....a Koi's DNA is not interested in ruling the world...jsut in ruling one koi to do its bidding and survive to breed in the future.
A myriad of scenarios that happen, and can happen have altered the Propogational strategy of a Koi's DNA and the program has been re-written billions of billions of billions.... of times and now it is this....the greater the variety of every aspect of a koi/carp the more likely it's DNA will be transported by a koi into the next reproductive period.
While I would like to discuss other aspects such as division of the numbers that are oriented to each group and the like I do not have the energy...musr on your own....A koi is different from every other koi because that is its Reproductive strategy. It prepares for all the variations that each spawning population should see by having millions of variations...it doesn't know which fish will have the right set of attributes to survive but ti knows the more variation their is the more likely one will survive."