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By Grant Valentine
August 10, 2025
Cyprinus carpio
The koi fish is the gorgeous Japanese descendant of the carp. With incredible lifespans which average around 40 years (but have historically been recorded in the hundreds), these gentle bottom feeders are more than just a pond ornament. Their beauty, though refined by man, is a testament to God as the artist of our world.
Photo by Alejandro Aro on Unsplash
What makes them unique?
“Koi” is actually directly translated from Japanese as “carp”, as their ancestors were colorful species of eastern carp, bred to be domesticated and radiant, with a white, orange, or black pattern in their scales. Their whisker-like barbs on the sides of their mouths help to give them a uniquely elegant image. The carp from which they were bred live natively in large rivers, ponds, or lakes in Japan. Wild koi (not their ancestor carp) are actually considered invasive in Japan and steal food from other species - like loaches, eels, and catfish - due to their size (up to 3ft. in length). So though they won’t directly attack other fish, it’s actually best for them to be domesticated as they were bred to be.
Like a tree, their scales have itty bitty rings which can be viewed under a microscope to somewhat reliably tell their age (a practice that was used on today’s animal ambassador).
Photo by Sora Sagano on Unsplash
Koi are freshwater fish with a notable ability to survive in frigid temperatures, up to but not including freezing (32°F). When the tops of their ponds freeze, they are able to retreat to the bottom where it’s slightly warmer to feed on algae for the winter.
What do they eat?
As omnivores, koi will eat almost anything that looks appealing, including algae, small fish, worms, plants (like water lilies), and of course, pellet food when domesticated. As members of the Cyprinid family, they possess pharyngeal teeth toward the back of their mouth which they use to chew their food. Sort of like your molars.
How do they reproduce?
Every May/June, wild koi who have reached sexual maturity (between 3 and 6 years old, different for everyone) will breed. Females stick their eggs on a plant, rock, or any suitable underwater surface. Male koi will fertilize the eggs, and they will typically hatch within 3-7 days. Their children spawn as itty bitty larvae, and will stay in warm, calm areas until they grow big enough to handle rougher conditions.
Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Cyprinus
Species: carpio
"Six carp swimming beneath wisteria", by Tsukioka Yoshitoshi in 1889
Creatures of Culture
Koi have a special place in Japanese culture, not only as a colorful sight piece, but as a symbol for courage. For centuries, they have received a similar reverence to Samurai, as koi are seen as brave and unrelenting, with the ability to swim upstream and even up small waterfalls.
In popular media, Avatar: The Last Airbender features a pair of spirits named Tui and La who take the form of black koi fish.
Scripture Spotlight
“So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it, according to their kinds, and every winged bird according to its kind. And God saw that it was good.”
Genesis 1:21 (NIV)
Animal Ambassador
Beautiful Hanako is today’s Animal Ambassador, and she is the oldest koi fish to have ever lived (that we know of). She was born in 1751 and lived an astonishing 226 years until her passing in 1977, making her not only the oldest koi fish but one of the oldest recorded vertebrates. She grew to be over two feet long and 17 lbs, and she hailed from Mt. Ontakein in Japan. It’s rumored that the crystal clear pond water from the mountain, alongside the loving care of the Koshihara family - inheriting her as she outlived their generations - are the reasons for her incredible age. According to her final owner, Dr. Komei Koshihara, she would come when called and present herself to be petted. She was returned to her Creator peacefully in the care of Dr. Koshikara on July 7th, 1977 (which is 7/7/77, uniquely enough).
Conserving God's Creations
While koi are domesticated around the world, they are mostly found wild in Japan. Their conservation status is Vulnerable, and this is mainly due to pollution and overfishing.
Doing your part by picking up litter you see washed up or floating in ponds, lakes, and rivers can mean a world of difference to these majestic creatures.
Similarly, when fishing in those areas, be careful to be safe! Make sure the fish you catch are not dropped, returned to the water with any new articles (such as a hook in its mouth), or in a different location than where they were caught. Oxygen deprivation occurs quickly when you remove a fish from water, so be sure not to keep them out any longer than you can hold your own breath. Though we rule over every living creature (Genesis 1:28), we are also called to care for God’s perfect creation and keep it fruitful so that future generations can enjoy it as we do.
Sources
⬤ KoiKeeper ⬤ Smithsonian National Zoo ⬤ PetMD ⬤ Bokksu ⬤
Header photo by Kyle Loftus on Unsplash
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