In a landmark achievement for Japan’s fisheries science, the Kinki University Fisheries Research Institute in Shirahama, Wakayama Prefecture, announced that it has successfully completed the world’s first full-cycle aquaculture of blackthroat seaperch (Akamutsu) at its Toyama Experimental Station in Imizu City, Toyama Prefecture.
The accomplishment marks the 30th fish species for which the university has achieved complete aquaculture—an achievement that allows fish to be artificially hatched, raised to maturity, spawned, and re-hatched without relying on wild stocks. The breakthrough is expected to pave the way for stable, year-round production of one of Japan’s most prized luxury fish.
Naotaka Nakamura, a technical staff member at the Toyama Experimental Station and Keitaro Iedo, director of the Kinki University Fisheries Research Institute
A Rare Deep-Sea Delicacy
Blackthroat seaperch (Doederleinia berycoides), known as "fatty white meat" or Akamutsu in Japan, inhabits waters less than 100 meters deep in the Sea of Japan. Adult fish typically reach 20–30 centimeters in length. Revered for its rich fat content and delicate flavor, the species commands high prices in upscale restaurants and sushi establishments.
However, wild catches are limited primarily to August and September, and annual landings are small, making it a rare and expensive commodity. Until now, sustainable aquaculture had proven elusive.
A 106-day-old blackthroat seaperch fry (provided by Kinki University)
A Decade of Research and Setbacks
The project began in 2015 with funding support from Kindai University President Hayato Takenaka and collaboration with the university-affiliated venture Armaline Kindai in Shirahama. Artificial fertilization and hatching were first achieved in 2016, but mass production and survival remained major hurdles.
Researchers faced repeated fry mortality due to the species’ delicate nature. Blackthroat seaperch are highly sensitive to environmental stress—thunderstorms, tank vibrations from passing trucks, and fluctuations in oxygen levels led to frequent losses.
By carefully adjusting oxygen concentrations and fine-tuning tank conditions, researchers improved survival rates dramatically—from an initial 0.1% to approximately 20% in later trials.
Successfully cultivated blackthroat seaperch fry (122 days old, approximately 4cm long, photographed on February 5th)
In 2022, the team successfully produced approximately 10,000 seedlings, followed by over 30,000 in 2023. However, disaster struck when the Noto Peninsula earthquake damaged tanks and pipes at the Toyama facility, causing power outages and mass fry deaths. Despite this setback, a small number of surviving juveniles allowed research to continue.
Breakthrough in Full-Cycle Farming
Using three-year-old farmed fish as broodstock, researchers attempted egg collection through both natural maturation and hormone-induced spawning beginning in August last year. While natural spawning occurred, fertilization did not succeed.
In contrast, hormone treatment administered to six female fish resulted in successful spawning. Over eight spawning sessions, researchers collected approximately 360,000 eggs. Artificial fertilization and hatching succeeded on October 6, completing the full-cycle aquaculture process for the first time in history.
A fertilized egg 29 hours after fertilization, one hour before burrowing. The egg is just under 1 mm in diameter. (Photo courtesy of Kinki University)
Currently, about 7,000 fully farmed fry are being raised. These fish are expected to mature within three years, forming the next generation of broodstock.
Toward Commercialization and Genetic Improvement
At a press conference, Director Keitaro Iedo expressed surprise at the pace of progress. “We thought it would take much longer,” he said. “Even after we achieved artificial hatching, repeated deaths during rearing continued. Producing 10,000 fry in 2022 was our first major breakthrough.”
Despite the success, challenges remain. More than 90% of artificially hatched fry are male, while females grow significantly faster and larger. Researchers are now exploring techniques to increase the proportion of females, potentially through selective breeding or hormonal methods.
Growth speed is another issue. Compared to species such as yellowtail and red sea bream, blackthroat seaperch grow more slowly under current aquaculture conditions. Future research will focus on:
Selective breeding to enhance growth rates
Improved feed formulations
Refined disease-prevention methods
Stable, high-volume egg production
The institute aims to begin supplying juvenile fish to aquaculture operators within five years, with full commercial distribution expected within eight years.
A Sustainable Future for Luxury Seafood
Kinki University has long been a pioneer in aquaculture innovation, previously achieving breakthroughs in species such as flounder, yellowtail, and bluefin tuna. The successful farming of a deep-sea species like blackthroat seaperch represents a new frontier.
Baby Akamutsu Very good taste，Fish bones are the soul
As climate change drives rising ocean temperatures and pressures wild fish stocks, land-based aquaculture systems offer greater environmental control and sustainability. By eliminating reliance on wild broodstock, the university’s method supports resource conservation while stabilizing supply.
The first harvest of three-year-old parent fish will soon be served as “Japan’s first farmed blackthroat seaperch” at the university-operated restaurants in Grand Front Osaka and Ginza, offering diners a preview of what may soon become a year-round delicacy.
With science overcoming both biological challenges and natural disaster, Japan’s luxury seafood market may be entering a more sustainable—and more accessible—era.
.png)
At a press conference, Director Keitaro Iedo expressed surprise at the pace of progress. 
Print
