Koi: The "Living Jewels" of the Seattle Japanese Garden
By Corinne Kennedy
Koi in the Seattle Japanese Garden’s central pond. (photo:Aurora Santiago)
Like so many gardens in Japan, our Seattle Japanese Garden features a central pond animated by colorful koi. These beautiful fish have been called “living jewels” and, in the words of former senior gardener Jim Thomas, “underwater rainbows”. Adults as well as children love feeding them, mesmerized by their slow, graceful movements.
Koi are an ornamental, domesticated variety of the common carp, a dull gray or blackish food fish native to freshwater areas around the Black, Caspian and Aral Seas. With time, this important and adaptable food source was introduced throughout the temperate world. Wild populations are now present in North America, South America, Africa, Europe, and Asia. Although most are gray, color mutations occur naturally.
Carp were first domesticated in 4th century China, where such color variations were noticed and appreciated. The fish, however, were raised only for food. Domestication then spread to Japan, where the earliest known instance of breeding carp for ornamental purposes began with rice farmers in Niigata Prefecture. They kept koi in their rice paddies as food fish, and over time observed fish with new and attractive colors and patterns. Choosing favorites, they began selectively breeding them, a process that involved not only carefully selecting parents with desirable qualities but also culling unacceptable offspring. The word “koi” is derived from the Japanese word for carp, and the new fish were called nishikigoi, which means “brocaded carp”. They became important features of garden ponds, and their images appeared in drawings and paintings of the period.
These beautiful new fish were valued primarily for their brilliant colors, attractive patterns, and serene, graceful presence. Adaptability, ease of care, and longevity increased their appeal. They also became symbols of strength, good luck and prosperity. Beginning in about 1914, koi breeding spread to other areas of Japan and to temperate rivers and lakes worldwide. Over one hundred distinct and recognizable varieties of koi have been created, differentiated by their colors, patterns, and scales. Incredible progress continues to be made, even in the last twenty years. However, some newer varieties – including ghost, ogon and butterfly koi – are not considered true nishikigoi.
Koi colors result from chemicals in their skin cells, not from their transparent scales, and include white, black, red, orange, yellow, blue, cream, and metallic golds and silvers. A layer of reflective skin cells is present in some koi, resulting in a mirror-like appearance. Varieties are further grouped into sixteen general classes or categories.
The most popular category is arguably Gosanke, which includes the Kohaku, Taisho Sanshoku and Showa Sanshoku varieties, sometimes referred to as “the big three”. Kohaku, white with a red pattern, remains the most popular variety in Japan, but body shape is considered even more important there. In the U.S., we tend to value color and pattern above all else.
The thirty-five to forty koi in our Garden are considered “pond quality” – pretty but not valuable – and were given to us by hobbyists and breeders. “Show quality” koi, on the other hand, are highly valued and expensive. They are evaluated according to three main criteria: ideal body shape and proportions, purity of color, and an interesting pattern with well-defined edges.
Although koi are highly adaptable cold-water fish, they require water temperatures that are above about 38 degrees F. In regions with harsh winters, pond water should be at least 4 ½ feet deep. Our Garden’s pond has an average depth of about four feet, with several much deeper holes, which is sufficient for keeping koi in the Puget Sound area. During the winter months, the koi remain at the bottom of the pond, their metabolism having slowed to a sedentary state (torpor) that resembles hibernation. With a digestive system that has almost stopped functioning, they live off stored fat, taking in only a few calories per day. When the water warms, their appetite returns.
Koi are omnivores and bottom-feeders. Lacking teeth, they feed on small insects, crustaceans, and plant materials. Although not cannibalistic, they eat their own eggs and fry, which they fail to recognize as fish until they’re an inch or two long.
Feeding the koi in our Garden’s pond. (photo: Galen Ogden)
Beginning in early May, and throughout the warmer months, visitors to the Seattle Japanese Garden can purchase “koi chow”, commercial pelletized koi food that supplements their diet. This kibble is small, nutritious, and designed to float. Feeding koi remain at the surface and highly visible. When they see visitors on the Garden’s two feeding “stations”, the zigzag plank bridge and moon-viewing platform, they form a mass of gaping mouths, color, and movement. Both children and adults are entranced by their vitality and beauty! We stop selling koi food when the weather cools in fall because koi lack the enzymes needed to digest food safely in cold temperatures.
The average size of adult koi is about eighteen inches, but lengths of over three feet are not unknown. Size is determined by food supply and pond water quality – maintained by pump and filtration systems, and by aquatic plants that take up excess nutrients from fish waste. Under ideal conditions, koi reach adult size in about three years, then their growth slows considerably. Koi expert and Certified Koi Keeper Monte McQuade believes that the average lifespan in the Puget Sound area is about twenty years. And the upper age limit for koi? According to the Smithsonian’s National Zoo, “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.” [https://nationalzoo.si.edu/animals/japanese-koi]
When young, males and females are difficult to tell apart, and never develop identifying colors or patterns. However, the shape of their pectoral fins (just behind the fish’s head, on either side) is different: males have pointed fins, in contrast to the rounded ones of females. In addition, females have a T-shaped marking in the vent area on their undersides. And, of course, egg-carrying females are noticeably plumper. Fertilization takes place only after a brutal spring ritual: males bumping females against the rocky edges of the pond, causing 20,000 to 40,000 eggs to burst out from the female’s body! Fertilized eggs hatch within a few days, but those that survive grow slowly during their first year. Most are eaten by predators – adult koi as well as raccoons, frogs, turtles, and birds. Among the latter is the great blue heron, perched on a rock jutting out of the pond – clearly on the lookout for baby koi! Mature adults are usually too big to be snatched or eaten.
Koi are a schooling fish. They’re social creatures, and according to McQuade, “they need a buddy.” Their temperaments are mellow, and they do not fight among themselves. In general, males tend to be more aggressive and larger fish more friendly. Different varieties have different personalities, with some being wilder and braver and some more docile. McQuade tells us that his fish recognize him.
In some countries, koi released into the wild have damaged waterways and depleted aquatic plant life. Constantly on the move, they stir up the water and increase its turbidity, ruining it for swimming or drinking. Eradication efforts have been mostly unsuccessful.
Despite this environmental concern, koi remain a wonder and delight in the ponds of Japanese-style gardens. They remind us of the rich diversity of nature from which they came and of our efforts to preserve and re-create such beauty and grace. Visitors to our Garden will again experience the vibrant aliveness of these special creatures. Whether or not you’re able to visit, please hold the koi – and the joyful awareness they awaken within us – in your hearts and memories.
Corinne Kennedy is a Garden Guide, frequent contributor to the Seattle Japanese Garden blog, and retired garden designer.