Koi fish are colorful, ornamental versions of the common carp. Though carp domestication is believed to have begun in China as far back as the 4th century, modern Japanese koi are believed to date back to early 19th-century Japan where wild, colorful carp were caught, kept and bred by rice farmers. There are now dozens of different color varieties of koi. They have an average lifespan of 40 years, and it is believed that the oldest-known koi lived to be nearly 230 years old. The age was determined by testing the fish’s scales, which produce growth rings much like a tree.
A common misconception is that koi are large goldfish; although koi and goldfish are both domesticated from carp, they are distinct species. While carp are popular with anglers, koi are bred for ornamental ponds. Koi and goldfish are the most popular freshwater, ornamental fish throughout the world. The koi breeding industry can be quite lucrative, with rumors of individual show-quality koi selling for hundreds of thousands of dollars.
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Koi are the close cousin of common carp, so all carp flies and tactics apply. Basic carp patterns, eggs, San Juan worms, hybrids, backstabbers and carp ticklers will all do the trick. Carp are already known as being an incredibly difficult species to catch on the fly, and koi can be even tougher. They have spent their entire lives being bright colored and easily seen by predators. These fish spook at the slightest sound or profile approaching from the bank. Koi can be face down in the mud and tailing, and they will take off like a dart as soon as you poke your head up to attempt a cast.
If you are able to sneak up and make a presentation, you will want to land the fly a decent distance beyond the fish so they do not hear it hit the water. As the fly slowly sinks, you will need to find the delicate balance of stripping it in front of the fish without moving it in too quickly. It needs to look like the fly is naturally drifting into the strike zone.
Since koi are usually stocked as a decorative fish or used for water quality control, they are usually found in cleaner water. If this is the case where you are fishing, smaller tippet is key. When the water is clear enough for the fish to see your line, they will definitely avoid it. Use a very light tippet and keep your drag very loose. Once you set the hook, some of these fish can take off like a rocket. Make sure to inspect your tippet for abrasions after every fish. Since you don’t usually use such light tippet for fish of this size, the line can really take a beating. Getting a take is few and far between, so switch out tippet frequently to avoid being snapped off when they do hit.
Matching your clothes to your surroundings can increase your chances of sneaking up on these fish. Blue shirt on sunny day, light gray on a cloudy day, or green if there are a lot of trees around you. Anything you can do to help hide your profile to what is behind you. Once you see the color of the fish in the water, keep low and sneak up the best you can. Move slowly and take your time.
Since these fish spook so easily, use the natural surroundings to your advantage. Try to hide behind any trees or walls that my be around. Search the lake for any debris or foam that could be hiding fish. They use debris in the water to hide from you, but it also allows you to sneak up and get right up on top of them.
Another tip to sneaking up on these fish is fishing on windy days. Wind will normally put an end to a day of sight fishing, but these bright fish can still be seen in less than perfect conditions. The wind will make the surface of the water choppier, but this chop will also make your profile less visible to the fish.
You are more than likely going to see plenty of other species when sight fishing for koi, and all of them will be happy to hit a carp fly if presented correctly. This can provide a little entertainment if the stubborn koi are not cooperating. If you have the patience and the skill to stalk carp on the fly, catching other species on the fly will be a cake walk.
Please practice Catch & Release in urban settings to preserve these precious resources for other urban anglers.