Every year, as July draws to a close, Norio Terada and his fellow oyster farmers submerge hundreds of scallop shells strung on wire rings into the waters of Lake Hamana.
The tiny black larvae that attach to the shells will be harvested from the salty lagoon in about 18 months as full-grown oysters. But first they have to survive an increasingly hostile marine environment that in recent years has withered production and rattled fishermen around the country.
“Oyster farming has a history of more than 100 years. But this is the first time I’ve observed this much death,” said Terada, 64. A particularly devastating season three years ago yielded only one-tenth his usual intake.
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 U.S. National Oceanic and Atmospheric Administration, with marine heat waves pushing some areas near 100 degrees this summer.
The change in sea temperatures is also scrambling the migration patterns and behavior of underwater creatures, which means that blackhead sea breams here in coastal Maisaka are becoming more active during the winter months and feeding on Terada’s juvenile oysters.
It’s not just Terada who’s struggling with scarcity. Four decades ago, this sushi-loving country was one of the largest fishing nations in the world, catching more than 12 million tons annually in the 1980s. But Japan’s haul has steadily declined over the last 10 years, falling to a record low in 2022 of 3.85 million tons, down 7.5% from the previous year.
As fish make for cooler climates, some species such as the Pacific saury and flying squid are moving farther into open waters and out of the reach of Japanese fishermen, particularly as fuel prices rise. Others traditionally caught off Japan’s southern shores, like yellowtail or Spanish mackerel, are reappearing in northern waters, according to industry groups. Oftentimes, those fish have to be shipped back south to the regions more familiar with preparing them for consumption.
The subsequent rise in fresh seafood costs is hitting Japanese consumers and merchants hard. In May, food inflation hit a 47-year high, with the price of fish climbing 14.8% compared with a year earlier and outpacing an 8.6% rise in meat prices.
“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 $9.5 billion. That year, the Ministry of Agriculture, Forestry and Fisheries launched a plan to restore fishery production back to 2010 levels of 4.44 million tons by 2030 and boost breeding of new and strategic species such as grouper and yellowtail.
The ministry’s Fisheries Agency said it would also aim to offset the impact of climate change by promoting the electrification of fishing vehicles, the farming of species with higher heat tolerance and the development of strategies to help juvenile salmon survive harsher environments.