What are Koi?

Koi are best described as oversized goldfish, they are closely related to goldfish, and essentially that's what they are, oversized goldfish, although unlike goldfish koi can grow to over 36 inches in length and over 40 pounds.

The colorful Koi fish are ornamental, domestic varieties of the common carp, Cyprinus carpio. Yes, it's true, Koi are carp. This often catches people off guard, as carp are generally regarded as dirty, slimy, bottom dwelling, mud sucking, rough fish while Koi are beautiful, colorful, and elegant works of art, but alas they are just carp, and in fact the term "koi" refers to carp in Japanese. Well not just carp, Koi are designer carp.

A Quick History of the Common Carp

The common carp (Cyprinus carpio)

The common carp is a large omnivorous fish that can be found in abundance all over the world, and are persued for both sport and fishing. While they are considered a rough fish that are not commonly eaten in North America, they are a staple food source in many countries all over the world. Due to their (perhaps deserved) reputation as a dirty fish, carp are often smoked before eaten to improve their flavor.

Carp fishing has been steadily gaining in popularity in North America, carp are an abundant yet challenging catch and can grow to over 80lb in size and put up one hell of a fight.

Carp are also a nuisance, they are an invasive species not native to North America. Common carp are native to Asia and Eastern Europe, although they have been introduced into environments on every continent except Antartica. The common carp was intentionally introduced into Midwest waters as a game fish in the 1880s, in the United States they are a regulated invasive species which means introduction into the wild is prohibited and fish caught while angling may be returned to the same water body.

Common carp are one of the most damaging aquatic invasive species due to their wide distribution and severe impacts in shallow lakes and wetlands. Their feeding disrupts shallowly rooted plants muddying the water, they release phosphorus that increases algae, and the declines in water quality caused by carp in turn cause declines of aquatic plants needed by other fish and waterfowl.

In many places it is illegal to intentionally release Koi, goldfish, or any other non-native species into public waters. Not only is it harmful and negligent, it can carry stiff penalties and fines. It may be tempting to set your fish free, but it is a bad idea, don't do it! This includes using Koi or goldfish as bait.

Two Koi color variations

Origins of the Koi

Koi are believed to have originated from Eastern Asia. While references in literature date back to a 4th century Chinese book which mentions carp with various colors, koi breeding didn't become popular until the 19th century. Japanese farmers noticed some carp were more brightly decorated than others, picked out the most vibrant carp to decorate their ponds, and through selective breeding the Koi evolved.

Koi Fish Today

By the 20th century a wide variety of color patterns had been established, and today the possible color variations are limitless. Koi are now popular all over the world as pond decorations, although they still hold their highest popularity in East Asia. Although Koi collecting is often viewed as a snobby hobby of the social elite, Koi are resilient fish that will find comfort in the crudest of backyard ponds, and can be bought for as little as a dollar. Despite this, serious Koi collectors better have some bucks, top quality Koi fish have been sold for over $100,000 USD.