Typically, farmed cherry salmon are 1.5 to 2 kilograms at harvest but Smolt has managed to produce a 4-kilogram fish at its Miyazaki Prefecture facility.
This was achieved over three years of using heat-tolerant, selectively bred strain combined with an all-female triploid system.
Smolt’s high-temperature-resistant cherry salmon juveniles were developed over six generations of selective breeding.
They can grow stably at around 20°C, compared with conventional salmon that require water below 18°C.
At the same time, the all-female triploid technology suppresses sexual maturation, redirecting energy from reproduction to growth and allowing fish to continue developing over a longer period, resulting in larger sizes.
This breakthrough addresses long-standing challenges in both growth and climate adaptation, as rising sea temperatures increasingly threaten salmon aquaculture.
According to the Japan Meteorological Agency, the average sea surface temperature near Japan has risen by 1.33°C per century, nearly double the global average of 0.62°C.
The trend, which accelerated around 2010, has reduced suitable farming areas for traditional cold-water salmon, shortened growth periods, and increased the risk of heat-related mortality, particularly during summer months.
Against this backdrop, technological innovations that enable stable salmon production even under warming conditions have become an urgent priority for salmon farmers both domestically and internationally.
Smolt’s innovations enable stable, long-term cultivation even under these warming conditions, representing a potential model for climate-resilient aquaculture.
Size matters
Cultivating larger sizes could enhance the competitiveness of Japan’s farmed salmon industry both domestically and internationally.
Larger sized cherry salmon are more likely to be used in restaurants and specialty markets, opening up more opportunities.
“Cherry salmon are more difficult to grow to large sizes compared to Atlantic salmon, masu salmon, or trout salmon commonly found in the market. However, their taste is exceptionally delicious. Going forward, we will optimise the cultivation period for mass production, aiming to establish a production system where cherry salmon is recognised worldwide as a delicious fish,” said Smolt CEO Ken Ueno.
Beyond increasing size and market value, the technology has wider implications for sustainable aquaculture, Smolt believes.
Rising ocean temperatures are a long-term challenge, and the ability to cultivate salmon stably under warmer conditions provides a crucial foundation for future industry resilience.
The technology also holds promise for sustainable salmon roe production. By enabling an all-female population, the triploid method supports large-scale, efficient roe harvesting.
