Click 'Read More' down on the right to see the full article
As you may know, koi originated in Asia as an offshoot of the common carp family. As far back as 2700 years ago, they were just dull mud-colored fish that were raised for food. Hundreds or thousands of fish would be kept in the same pond, and as early as 1000 years ago people noticed that a few of those fish had more attractive color mutations; some of those fish were spared the fillet knife and kept aside in personal garden ponds as living jewels. Over time, more and more exceptional fish appeared, and in 1820's Japan these exotic-looking carp acquired the name nishikigoi and the art of koi-breeding was established. People kept selecting the best of the best, and cross-breeding them to create more exotic-looking fish with each generation. Fast-forward to today and we now have 22 officially recognized types of koi, with countless variations and hybrids, and new varieties appearing all the time.
If all koi trace their ancestry back to Japan, why do sellers distinguish between domestic and imported fish?
The answer to that comes down to the breeders, and the particular breeds in which they specialize. Since Japan is where the art of raising koi first began, it makes sense that the most prized fish come from Japan where people have been honing their art for many centuries. They have been breeding koi since before America was even colonized. Those breeders have refined their techniques to raise the best-looking fish, and they have gathered many tricks and secrets throughout the years that have been passed down from generation to generation. They even pass down their fish, as koi have been known to outlive their human companions. As with any art form, the people raising the most beautiful koi often keep their tricks to themselves, ensuring they will have the best fish that command the highest value. This practice has cemented Japan as home to the worlds foremost authorities in koi breeding, although champion koi can be, and are, bred across the world.

Here in America, koi breeding has only been around for roughly 100 years. The fish that we have here come from the same ancestors as the Japanese koi, and are pretty much the same, genetically. Beyond any superficial differences, the main difference between domestic and imported fish tends to be their hardiness, with domestic koi generally being healthier and more vigorous. The main reasons for this come down genetics, adjustments to certain parasites and bacteria, and most importantly, stress from transportation.
The bloodlines and ancestry of imported fish can be traced back hundreds of generations, which isn’t that unbelievable considering their generations are so close together. Their lines have been carefully bred to create stabilized varieties, which has had the side-effect of straining their gene pool a little bit. They’re a little bit inbred, and I don’t mean that in a negative sense, because those fish are a lot prettier than the ones with a shorter genetic tree. However, that beauty comes at a price, the disadvantage of a weaker immune system. These fish are more susceptible to illness and parasites, having a more limited ancestral pool to improve upon. It is like the opposite of hybrid vigor.
That isn’t the full story, though. The difference goes beyond genes. It stretches into things like intensity, frequency and duration of their immediate lifestyle, which for imported fish means transportation. Due to its much longer duration, the intensity of their transportation is a lot worse. They begin their journey in the ponds in Niigata, Japan, up in the mountains. They come down from the breeder and are received by brokers and trans-shippers, where they’re briefly housed before being packed up again and then sent off to the airport to be shipped to America. After a flight lasting around 14 hours, they drop down at LAX. There they are re-bagged with fresh water and oxygen before being sent off again. Quite often, after LAX, they get shipped up to three additional times. First from the airport to the wholesaler, then from the wholesaler to the vendor, and a lot of times they get shipped yet again from the vendor to the consumer. These fish may be shipped as many as seven times! Sometimes less, but never fewer than three times.
That is very different from the domestic fish, because a lot of times the domestic fish come right out of the breeder pond and are brought to their end destination, which is the retailer, where they will stay comfortable until they are picked up by the purchaser or brought directly to the pond where they will live their lives. So the intensity and duration of transportation is considerably less for the domestic fish.
Although it is not as common as trauma during transport, another factor that distinguishes domestic fish from imports is their familiarity with different diseases. When those foreign fish get on the ground, they are not accustomed to some of the diseases here. Unlike the Japanese fish, our domestic fish have had generations to become adapted to the bacteria, viruses and parasites commonly found in America. The imported fish come over and go into some of our facilities and they’ve never seen a particular nella or bodo or parasite. When they’re exposed to it for the very first time, their immune systems have built up no antibodies to defend against it and it ravages them.
You may notice that people often assert the difference in hardiness is all about genetics, but that is only a small part of the picture. The primary factor is how they react to the stress of transportation. Their compromised health after such a long journey then complicates things as they acclimate to our environment and get used to the local germs. Once they have had time to settle in and adjust, the fish are pretty much equivalent as far as their vulnerability to diseases. After the first year, the domestic koi will only be about 5% less likely to be affected by disease when compared to the imported fish. Just as with other kinds of transplants, the most critical time is in the beginning. After the adjustment period, they’re not all too different from each other.
Do you have too many fish in your pond and would like us to help find them a new home? Have your koi outgrown their pond? Have they had lots of babies? One service we are pleased to offer to our clients is a program for fish adoption. We are able to foster unwanted fish and find them new homes, with all proceeds going to the Aquascape Foundation. Space may be limited in our foster pond; please call to make sure we can accommodate your fish.