Fatty ‘katsu’ fish may portend climate change, posing a threat to Japanese sushi

NAKATOSA, Japan, July 12 (Reuters) – Half a century ago, Takeo Nakago has been catching katsu tuna, or skipjack tuna — an indispensable part of Japanese cuisine, whether 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 the heavier katsu means more money, locals and experts say it indicates climate change and a threat to the katsu numbers already threatened by increased demand and poaching.

Register now to get free unlimited access to Reuters.com

“The fatty katsu must have something to do with the temperature of the water,” said the 70-year-old Nakajo. “I have a sense of urgency thinking what if Katsuo never comes to the bay.” (Photo essay: https://reut.rs/3AFtYSQ)

He’s also “never seen such a greasy katsu during this season of the year,” said Noriaki Ito, chef at the century-old Tsukasa restaurant in Kochi.

This is worrying, Ito added, because changes in the sea and climate have already wiped out some other fish, “including oysters called chambara gai, which 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 surface temperature of the bay in winter increased by 2 degrees Celsius in the four decades to 2015, local fisheries lab data show, and the fatter katsu may be caused by the presence of abundant prey in the warmer sea.

But in the long run, this warming may prevent the mineral-rich water from rising to the surface, causing the plankton and the small fish that feed on them to decline, resulting in fewer katsu, said Hideyuki Okida, an agricultural scientist and vice president of the University of Kochi.

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. Read more

Many fishermen have gone out of business in the past three decades, said Takahiro Tanaka, a fourth-generation owner of a fishmonger who calls himself “leg katsu” in Kuri, a district in Nakatosa Township.

He added, “We can distinguish the different tastes of katsu, just as ordinary French farmers taste a delicate wine…This place may be one of the last Japanese communities where katsu is part of everyday culture.”

But without Hunters, this won’t last,” Tanaka said.

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,” Nakajo said.

Sushi culture is in danger

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 have seen a catastrophic decline in landings over the past 10 years or so,” Okeda said.

“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, said the number of katsuobushi manufacturers in Kochi has been reduced from dozens about forty years ago to just a few.

“I’m not really sure if we can continue with that,” Takeuchi said.

Wasabi, the tangy radish that is essential to Japanese food, especially sashimi and sushi, faces similar production challenges. Read more

Masahiro Hoshina, 72, president of the local wasabi growers’ association, said typhoons and rising temperatures had hit production in Okutama, a mountainous area west of Tokyo.

“I am very concerned about the future of our cultivation,” Hoshina said.

The number of farmers in the area is 75% less than in the 1950s due to population decline, and unless something changes, some fear sushi itself will be endangered.

“The mixture of raw fish and spices, as in katsu and wasabi, is an art, and we must preserve them,” said Yukida. “I never want to think about the future” without them, he added.

Register now to get free unlimited access to Reuters.com

Additional reporting by Kantaro Komiya in Nakatosa; Additional reporting by Kim Kyung-Hoon and Irene Wang; Editing by Elaine Lays and Himani Sarkar

Our Standards: Thomson Reuters Trust Principles.

Leave a Comment

Your email address will not be published. Required fields are marked *