Butterfly Koi: Basic Facts to Know

Butterfly Koi: Basic Facts to Know

In certain circles, when you mention butterfly koi it’s like speaking out of turn in an audience with the Pope. You just don’t do this. Quite a few of the koi connoisseurs think of butterfly koi as “mutts,” and some say that butterfly koi aren’t even koi. Others, however, happen to think butterfly koi can be the finest koi in any collection, depending on several factors – size, pattern, and finnage.

First, let’s consider where butterfly koi originated. In the early 80s, a population of common, brown and grey carp with long fins were found in a series of canals and ditches in Indonesia. A company in New York took an interest and brought the fish into the U.S. and sold some. They did not sell well because they were ugly. However, an enterprising and curious group of breeders at Blue Ridge Fish Hatchery placed an order for a dozen of these fish to see what the heck they were. Ugly, with long fins, is what they discovered. Over the next several years they bred these large, long finned mutations with their finest regular-fin koi and made several discoveries.

The Relation of Size and Value

As Butterfly koi grow, they become more and more impressive because the fins keep growing until the blood vessels can’t sustain the fins to be any longer. The older the fish, the longer and more impressive the finnage. So, a full-grown butterfly koi looks like a long, slinky dragon moving through the water. Their barbels (whiskers) even grow long and can fork into elaborate designs.

Butterfly koi seem to lack some of the body size of regular koi, but the overall fish can run as long as 36 to 40 inches in the right pond with plenty of food. They are graceful and pleasant to watch swim.

Even better than that are black butterflies – which are, by far the coolest fish. They are seldom found, so the effect is rare and special when it happens. The black butterfly may be with or without scales. The rarest and most valuable of this type is the doitsu, karasu butterfly. This fish is black, has no scales, and has long fins.
Black Beauties

Black butterflies grow up and become very large because their genes are not as strained as some of the brighter colored fish. And if they have no scales, the body is a glistening jet-black. The fins keep growing until the entire fish is broad, and streams long black robes behind it. They look like a jet-black dragon.

Oh Those Fins!

In a discussion of butterfly koi, we should talk a tiny bit more about the fins. The butterfly koi fins are long because of a genetic aberration resulting in the length growth gene failing to turn off. In fish, the fins are supposed to grow to a genetically specified length, and then stop growing. But in the high fin mutation the fins don’t get the “stop growth” message and they keep growing. This happens in individual fish of many species from time to time. Some notable examples are Siamese fighting fish, Simpson’s hi fin swordtails, long fin oscars, and long fin black tetras. Any time the mutation is encountered and identified, it is bred into a species to see if it would make that species more economically important commercially.

Like any other koi, the fins of the butterfly koi are made up of dozens of rays of cartilage that radiate outward and support the fin. These rays generally grow very straight, but past the point of normal length they can grow wavy. The fish that grow straight rays even into the lengthier parts of the tail are more impressive looking and would be more valuable.

One problem with butterfly koi is that they are often handled the same way as regular koi. Broken fins and tails are par for the course by the time the fish is an adult. So, it’s normal to see bends and waves in the fins and tail of butterfly koi partly because of growing that way, but also because of netting-damage as a juvenile. As an adult, a split tail or fin often does not heal well and remains split. All of the above is irrelevant to the casual observer, the impact of the fish is exactly the same, but you might notice variations in fin quality and you may care enough to choose one fish over the other based on that.

The butterfly koi is a true koi. Despite this fact, the Japanese have shared some American purist’s distaste for these long fin beauties. Truth be told, the Japanese have usually reacted to any new color, at first, as an abomination. Eventually, they get used to it and accept it, and eventually love the diversity.

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