Koi words & farming
Nishiki Pond is built on how koi are really bred in Japan. This page covers where nishikigoi came from, how a farm’s year runs, and the words breeders use. Each one says where it turns up in the game.
Where koi come from
Koi are carp. The common carp came to Japan from China long ago, and for centuries it was simply food. Coloured koi, nishikigoi or “brocaded carp”, began in a few snowbound mountain villages in Niigata, around what are now Yamakoshi (part of Nagaoka) and Ojiya.
- Before 1800Black carp as winter food
Villagers kept plain black carp, magoi, in ponds and terraced rice paddies on the steep valley slopes. Heavy snow cut the villages off each winter, and the carp were a store of food.
- Early 1800sA red fish among the black
A carp with red markings turned up among the magoi. Instead of eating it, the farmers bred from it. Over generations, chance mutations and careful selection gave red, white, yellow and patterned fish.
- 1914The Tokyo Taisho Exhibition
Niigata koi were shown in Tokyo, and the attention they drew there (including from the young Crown Prince Hirohito) made them famous across Japan.
- After 1916Crossing varieties
Breeders began crossing different lines rather than keeping them pure, which produced many more colours and patterns. Today there are around a hundred varieties. Kohaku, Taisho Sanke and Showa, the Gosanke, remain the most prized.
- 2004The Chuetsu earthquake
A major earthquake wrecked Yamakoshi’s koi ponds and forced the villagers to leave. With help from breeders and koi keepers across Japan, they rebuilt within about three years.
- TodayA world industry
Koi from Niigata are exported around the world and are one of the prefecture’s biggest exports. A top show winner can sell for hundreds of millions of yen.
A Japanese farming year
The game’s calendar follows the real one, squeezed into four 30-day seasons.
The breeder picks the parents, the oyagoi, and puts them in a spawning pond with artificial weed or brushes. A big female lays hundreds of thousands of eggs, which stick to the brushes and hatch in about three to four days.
In the game: the breeding pond, spawning brushes, and eggs that hatch three days later.Fry are sorted again and again (senbetsu). The first cull comes a couple of weeks after hatching and removes most of them: bent, weak and off-colour fry. The best go out into the mud ponds, rich in natural food, from about May to October, where they’re sorted by size and colour.
In the game: first selection (day 6) and second selection (day 26).The ikeage, the harvest. Workers net the mud ponds, often starting at sunrise, and bring every fish in before the cold. Buyers visit the farms to choose koi.
In the game: harvest on autumn day 15. Every fry becomes a tosai.Koi spend the cold months in sheltered or greenhouse ponds until spring. In cold water they hardly eat or grow. Winter is also the season for the big shows.
In the game: the ponds rest and the winter market opens.Of roughly 200,000 fry from a spawn, a Yamakoshi breeder may keep only 500 to 1,000 to adulthood. In the game the mud pond holds 10 to 40 fry: think of them as the few that made it through the first cull.
How fast koi grow
Koi are cold-blooded, so they grow with the temperature. They grow best at 20–25°C, slow down below about 15°C and almost stop below 10°C. Most of a year’s growth comes in summer.
| Season | Water | Share of a year’s growth |
|---|---|---|
| Spring | 10–18°C, warming | About 15–20%, picking up in May |
| Summer | 20–26°C | About 55–60%, the main growing season |
| Autumn | 20°C falling to 10°C | About 20–25%, mostly early on |
| Winter | below 10°C | Next to nothing |
| Age | Real farm koi | Nishiki Pond (average genes, good care) |
|---|---|---|
| Tosai · end of year 1 | 12–25 cm | about 14 cm |
| Nisai · year 2 | 30–45 cm | about 38 cm |
| Sansai · year 3 | 45–55 cm | about 50 cm |
| Yonsai · year 4 | 55–65 cm | about 57 cm |
| Adult · 5 years and up | 60–75 cm, jumbo 80–90+ | up to 88 cm with top size genes |
Koi can spawn from about two or three years old, at around 30–35 cm. Serious breeders prefer parents of four years or more, which give bigger, healthier spawns and have already shown their quality. In the game a koi can join the breeding pond at 29 cm and spawn at 35 cm.
Selection and tobi
- Most fry are culled. It sounds harsh, but a pond can only feed so many, and every poor fish takes food from a good one. Breeders cull for deformity first, then colour, then pattern and skin.
- Tobi (“jumpers”) are fry that grow far faster than the rest and start eating their siblings. In a crowded mud pond one tobi can thin out a whole brood. Breeders pull them out early. Some are culled; some fast growers turn out to be very good fish.
- Runts lag behind and usually stay small. They’re among the first to go at selection.
- In the game, growth rate is a real gene. Bigger fry win more of the food, so a fast grower pulls further ahead each week and may become a tobi. Netting cards tag each fry as a tobi, big for its age, average or a runt, and the mud pond’s grading sieve lets you net a tobi out between selections.
Koi words
Every word the game uses, and a few more you’ll hear from koi keepers.
Sources
- Yamakoshi Nishikigoi farming, Japan Tourism Agency multilingual database.
- The history of koi in Japan, Tokyo Weekender.
- The art of koi breeding in Japan, Pond Trade Magazine.
- Koi fry rearing guide, Gensou Koi.
Growth figures are typical ranges. Real koi vary a great deal with water, food, pond size and bloodline.