For half a century, Takeo Nakajo has been catching katsuo, or skipjack tuna - indispensable in Japanese cuisine whether eaten raw, dried or used as a base for the broth.
But he and other fishermen in Kure, in Kochi prefecture in southwest Japan, have seen something worrying in the past two years - an unprecedented number of unusually fatty katsuo.
The number of farmers in the area is down 75% from the 1950s due to depopulation, and unless something changes, some worry sushi itself could be endangered.
"The combination of raw fish and spice, as in katsuo and wasabi, is an art, and we must maintain both," said Ukeda. "I never want to think about a future" without them, he added.
(Photo Editing Kezia Levitas; Text Editing Elaine Lies and Himani Sarkar; Layout Kezia Levitas and Marta Montana Gomez)