Kawai and Iyoda remove a metal net used to protect their clams from predators as sea temperatures rise in Maisaka. — Photos: STEPHANIE YANG/Los Angeles Times/TNS
One critical threat is warmer waters, which stunt the growth of oysters and other aquatic organisms as oxygen levels decline. The average temperature of the world's ocean surface reached a record high in August, according to the US National Oceanic and Atmospheric Administration, with marine heat waves pushing some areas near 100°F this summer.
"The response of the ecosystem is changing. It's becoming very difficult to predict which kinds of species will increase," said Shin-ichi Ito, a professor with the Atmosphere and Ocean Research Institute at the University of Tokyo."Fishermen can adapt. But for the food industry – fish produce, seafood materials – it is very hard to adjust because most of the companies are very small."In 2021, Japan's fishing and aquaculture industry generated about US$9.5 billion .
Others blame the declining catches on human intervention such as overfishing, which the government is trying to curb through tightened quotas, or Japan's rigorous filtration system, which returns seawater to the ocean without nutrients vital for marine life. In another area, clam fishermen have tested similar measures to prevent sea bream from eating their potential harvest, too, stringing mesh across poles in a small patch of shallow water. But they found that the material tore too easily, leaving the net riddled with holes.
The Fisheries Agency is trying to help fishermen adjust to shifts in marine life by teaching them to go after different kinds of fish, which requires their time and money to learn unfamiliar techniques with new equipment. Even then, some species aren't worth the investment.