Every October, as temperatures drop and Niigata’s mountains change colour, Japan’s koi breeders net their mud ponds. Out come koi that have spent the summer growing in natural ponds, unseen until harvest time. For dealers and hobbyists, this is the highlight of the koi calendar: the autumn harvest.
This year, Exclusively Koi’s Ryan Stoddart will once again be there for the full six weeks, from 2nd October to 17th November. It’s an intense, fast-moving period where the best koi of the season are revealed, sold, and shipped across the world.
What the autumn harvest is really about
At its core, the autumn harvest is when breeders pull their ponds and reveal koi that have been raised through the summer months. Fish from two to five years old, unseen since spring, are harvested, sorted and made available for selection.
It’s also when customer koi are returned. Many enthusiasts pay an azukari fee for their fish to stay in Japan over the summer. “Clients leave koi with breeders to benefit from the natural mud pond environment. At harvest, you see the results, a koi that’s grown from one to two years old, or from three to four. It’s like getting to see the finished art.”
Breeders track everything meticulously. Sizes, weights, photographs, and growth notes are compared against what emerges from the pond. For them, the harvest is both a celebration and an evaluation of the season’s work.
Why six weeks matter
Traditionally, dealers would spend two or three weeks in Japan. Ryan now stays for the entire harvest window. The shift reflects changes in the industry and his own approach.
“The business has evolved,” he says. “Buying styles are different now. For me, it’s about covering the whole period, making sure nothing is missed. Being there the whole time gives better results for clients and more control over quality.”
The extra time isn’t just about the sheer number of farms he visits, around 30 to 40 across the country, but also the way the harvest unfolds. In Niigata, the epicentre of koi breeding, one phone call can upend the day’s plans. “It’s fast and furious. You can be at one farm, then suddenly racing to another because something special is being harvested. That unpredictability is part of the buzz.”
The growing ponds of Niigata
Makoto Tanaka - NND Koi Farm
Mud ponds versus concrete ponds
Not all koi are raised in mud ponds. Many breeders, especially in the south, use concrete ponds to grow fish year-round. Indoors, conditions are tightly controlled: no predators, regulated feeding, and stable water quality.
Mud ponds, however, remain the gold standard. “Every year I still get the same buzz. There’s nothing like pulling a koi from murky water and seeing how it’s developed. Money can’t buy that feeling,” Ryan says.
The process is demanding. Farmers must monitor ponds daily, watching for predators, water levels and climate shifts. Rainfall is essential, without it, ponds can evaporate in the summer heat. Larger farms with greater resources invest heavily in their ponds, producing consistent results. Ryan highlights Makoto at NND as one of the best. “His ponds are stunning. The results blow me away every year. If you want to put your money where your mouth is, buy from Makoto.”
Life in harvest season
For dealers, harvest season is relentless. Seven days a week, early starts and late nights, with plans that change constantly. Ryan describes it as “a blur.”
“You wake up, grab a coffee, and head for the mountains. You might have appointments lined up, but it only takes one phone call to change everything. That’s Niigata. You don’t get that pace anywhere else.”
Preparation begins days in advance, with breeders cutting off food and then pulling koi from ponds. Fish are brought back to farms for selection, often under strict systems to keep things fair. In many cases, buyers draw chopsticks to determine the order in which they choose their koi.
“It can be frustrating, but it’s fair. Demand is so high now that farms have to balance long-term customers with newer buyers spending serious money. Years ago it was more relaxed, but today the harvest is busier than ever.”
Otsuka Yoshikazu at Otsuka Koi Farm
Staff examine and log the fish
The art of selection
Choosing koi at harvest is as much instinct as it is science. For Ryan, it’s second nature. “Because I've been doing it from such a young age, it's a very natural process for me to look and filter out the koi very fast in terms of what I'm looking for. If there are 100 fish in a bowl, I’ll already have my eye on the next one while I’m picking the first. It’s just how my brain works.”
For beginners, the advice is simple: start with the body. Look at the line, shape, fins and any deformities. Pattern comes later. “Most hobbyists go straight to pattern, and that’s natural of course, you’ve got to like what you see. But as your knowledge grows, body and genetics come first.”
“If someone wants a fish to hit 90cm, you start with body and genetics.”
Purpose shapes selection too. A koi destined to grow large must have the right structure and bloodlines. “If someone wants a fish to hit 90cm, you start with body and genetics. Pattern comes after. Even a solid nisai without the right attributes won’t get there.”
At the top end, standards are ruthless. Show-quality koi must tick every box. Lower-priced fish may compromise on certain elements, but the fundamentals of body and health always matter.
Show potential and preparation
Everyone dreams of owning an award-winning koi, but harvest time isn’t when they shine. Fresh from the pond, koi are in a raw state. Shiroji can have a yellow tinge rather than the pure white hobbyists expect, and beni often looks under strain from heavy summer feeding and high temperatures. Colours and skin simply aren’t at their peak.
“Preparation makes the difference,” Ryan explains. “Before shows here in the UK, we spend two or three weeks getting koi ready. Water quality, feeding, environment. Everything is fine-tuned. That’s what elevates a fish to show condition.”
Over the years, Ryan has selected koi at harvest that later became champions. The key is experience: recognising not only what a fish looks like in that raw state, but what it can become once conditioned and raised correctly.
What customers gain
For UK buyers, Ryan’s time in Japan translates directly into quality and access. “It’s simple: they get the best fish,” he says.
While UK breeders can produce some excellent koi, Japan’s farms offer something unique: pedigree bloodlines. Names like Sakai, Momotaro and Dainichi dominate the market, with buyers often asking about lineage before anything else.
“It’s like Crufts. If you’re buying a pedigree dog, you want the best bloodline. It’s the same with koi. At the top end, bloodlines guarantee growth, body and colour. That’s what clients are paying for.”
Top breeders even publish books charting their bloodlines, while smaller farms often use parent stock from the giants. The result is decades of refinement, creating koi with qualities that simply can’t be replicated overnight.
The buzz of October
Ultimately, the magic of the autumn harvest lies in its atmosphere, the speed, the unpredictability, and the moment a koi is lifted from the pond.
“The buzz of leaving a fish in Japan through the summer, knowing the risks, then seeing it come out in October, nothing else compares. If you’re there in person, it’s unbeatable.”