For half a century, takeo nakaju has been catching katsu, or skipjack tuna – a staple in Japanese cuisine whether eaten raw, dried, or used as a base for broth.
But he and other fishermen in Kore, in Kochi Prefecture in southwestern Japan, have seen something troubling in the past two years: an unprecedented number of unusually fatty katsu.
While heavier katsu means more money in the short term, locals and experts say it’s a sign of climate change, and a risk to katsu numbers already threatened by rising demand and Overfishing.
“The fatty katsu must have something to do with the temperature of the water,” says the 70-year-old. “I have a sense of urgency thinking what if Katsuo never comes to the bay.”
He’s also “never seen such a greasy katsu during this season of the year,” says Noriaki Ito, 106-year-old chef at Tsukasa Restaurant in Kochi.
This is worrying, Ito adds, because changes in the sea and climate have already wiped out some other fish, “including oysters called chambara gai that were Kochi’s specialty.”
Originally from tropical waters, some Pacific Katsu migrate north on a warm ocean current each spring, making the arc-shaped Bay of Kochi a fertile fishing ground.
The average winter surface temperature of the bay increased by two degrees Celsius in the four decades to 2015, local fisheries lab data show, and Katsu may be the fattest due to abundant prey in warmer sea.
But in the long term, this warming may prevent the mineral-rich water from rising to the surface, leading to a decline in plankton and the small fish that feed on them. This will reduce the number of katsu, according to Hiroyuki Okeda, an agricultural scientist and vice president of Kochi University.
It comes as Japan’s aging population threatens the sustainability of local fishing and related businesses such as the production of dried and fermented katsuo and wasabi radish – an eye-watering condiment tucked under fish in a piece of sushi.
Many fishermen have gone out of business in the past three decades, says Takahiro Tanaka, a fourth-generation owner of a fishmonger who calls himself “Katsu’s Legs,” in Kuri, a district of Nakatosa Township.
“We can distinguish the different tastes of katsu, just as ordinary French farmers might taste the smallest of details. wine,” he adds. “This place may be one of the last communities in Japan where katsu is part of everyday culture.
“This won’t last without fishermen,” warns Tanaka.
The hunter Nakajo also angered the elderly community and a few of his successors. “I asked my grandson if he would take the position, but now he is studying to work in a government office,” says Nakajo.
How is climate change threatening sushi more broadly?
Overfishing has already hit catch numbers and dealt a blow to fishermen in Kochi who stick to traditional monopole fishing methods versus large-scale trawling across the western Pacific.
Government data shows that fishing numbers in Kochi were only a quarter of their peak in the 1980s.
“We’ve seen a catastrophic decline in landings over the past 10 years or so,” Okeda says.
“An increasing number of people fear that we may not be able to eat katsu in the near future if things continue like this.”
Already suffering is the production of katsuobushi, the dried and fermented katsu, which is often used as a condiment shaved over traditional Japanese dishes or as a broth base.
Taichi Takeuchi, who runs one in the USA town, says the number of katsuobushi manufacturers in Kochi has been down from dozens about forty years ago to just a few.
“I’m not really sure if we can continue with that,” he adds.
Wasabi, the tangy radish that is essential to Japanese food, especially sashimi and sushi, faces similar production challenges.
Masahiro Hoshina, 72, president of the local wasabi growers’ association, said typhoons and rising temperatures had hit production in Okutama, a mountainous region west of Tokyo.
“I am very concerned about the future of our cultivation,” Hoshina says.
The number of farmers in the area is down 75 percent from the 1950s due to population migration, and unless something changes, some fear sushi itself will be endangered.
“The combination of raw fish and spices, as in katsu and wasabi, is an art, and we must preserve them,” says Okeda. “I never want to think about the future” without them, he adds.