Koi or Common Carp

Cyprinus carpio

"Fair Choice" Pet Fair Choice

Common Carp are large, greenish-brown freshwater fish native to Asia and eastern Europe. They are the first known domesticated fish, farmed for food over 2,000 years ago in ancient Rome. Common Carp have been successfully introduced all over the world for aquaculture, often causing serious environmental damage in their non-native habitats. They tolerate a wide range of water temperatures and conditions, and are omnivorous, eating algae, worms, plants, snails and small insects.

For centuries, Common Carp have also been bred into colorful, highly ornamental pond fish called Koi. Koi are usually bred for very specific patterns and color combinations, usually including white, gold, orange, black or blue, When released back into the wild, Koi populations usually revert back to their natural olive-green or brown color within a few generations. Common Carp are hardy and grow quickly, up to four feet long. In the wild, Common Carp often live for 15 to 20 years. In captivity, Koi regularly live for 50 to 70 years, and one famous fish in Japan lived to be 226 years old!

Did You Know?

In captivity, Koi regularly live for 50 to 70 years, and one famous fish in Japan lived to be 226 years old!

Source Sustainability Best Choice

Does the harvest for wildlife trade or captive breeding of this species harm wild populations?

Little Cause for Concern

Koi are almost exclusively bred in captivity, and therefore the pet trade does not threaten native wild populations. Wild Common Carp populations are widespread throughout their native range.

PetWatch Recommendation:

Check that the store purchases their fish from a reputable supplier that exclusively sells captive-bred Koi. In addition to reducing threats to wild populations, buying fish that are captive bred will generally insure that you get healthier and longer-lived fish than those that are wild-caught.

Invasion Threat Worst Choice

Does the release or escape of this species into the wild harm the environment and/or economy?

Significant Cause for Concern

Common Carp/Koi have been successfully introduced in many regions of the world, where they cause significant environmental harm. Thriving wild populations now exist throughout North America, South America, Europe, Africa, and Australia. Carp/Koi are usually introduced intentionally for fishing and aquaculture. Because Carp are hardy and able to tolerate wide ranges of temperature, food type, and water quality, they are often very successful in non-native habitats.

Common Carp/Koi root and dig in sediments, increasing the muddiness of waters where they are introduced. This often causes the death of aquatic plants and reduced survival of other aquatic species. Common Carp/Koi have also spread harmful fish parasites to North America, South America, and Australia.

PetWatch Recommendation:

Always keep your Common Carp/Koi inside a safe and secure aquarium. Never release a pet into the wild.

Animal Welfare Fair Choice

Does harvest, captive breeding, transport, or being kept as a pet harm individual animals?

Some Cause for Concern

Koi are relatively easy to keep in captivity and can even tolerate poor water quality for short periods of time. They may become more susceptible to disease in overcrowded conditions. Koi are not suited for indoor aquariums and do best if kept in outdoor ponds. Koi are long lived in captivity (up to 70+ years) and thus require a long-term commitment to care.

PetWatch Recommendation:

Before acquiring a Koi, be sure to research its specific care requirements.

Health Threat Fair Choice

Does this animal pose a health risk to native wildlife, humans, livestock and agriculture?

Some Cause for Concern

Common Carp/Koi carry parasites that can harm other fish. Koi are also known to carry Mycobacteria that can cause disease in other fish and skin infections in humans. Even healthy-looking fish may be carrying these bacteria. People with compromised immune systems are particularly susceptible to these skin infections, commonly known as “fish-handlers disease.”

PetWatch Recommendation:

Due to the potential for disease transmission, always wash your hands after handling a fish or touching the aquarium water. Ask for proof of a clean bill of health and obtain a list of any medical treatments the fish has received.

EcoHealth Alliance works at the intersection of ecosystem, animal and human health through local conservation programs and develops global health solutions to emerging diseases.
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