SAPPORO (Kyodo) -- There is trouble on the horizon in the northernmost prefecture of Hokkaido, where poor fishing conditions triggered by global warming are endangering Japan's prized salmon -- widely considered one of the country's favorite seafood.

A researcher has warned that climate change is forcing Hokkaido's chum salmon, which make up the bulk of Japan's salmon catch, into a losing battle with a relative for food, hindering their return in large numbers to spawn in the rivers where they were released.

Masahide Kaeriyama, a salmon ecology expert and professor emeritus at Hokkaido University, sounded the alarm, warning, "If this trend continues, there will be no more salmon in Japan in the next century."

According to the Hokkaido government, salmon numbers peaked at 56.47 million in 2003 but have since plummeted to less than a third of that, reaching 15.62 million in 2024 -- the second-lowest count on record since 1989.

The prolonged decline has forced seafood retailer Maruichi Suisan to hike the price of its processed salmon jerky snack, "Sake Toba," by 20 percent this winter.

"We kept the price unchanged for over 10 years, but with poor catches, we had no choice," said shop manager Kei Numahata with resignation at the Nijo Fish Market, bustling with tourists and locals in Sapporo's Chuo Ward.

The tough and chewy salmon fillets, known to pack natural umami flavor, have long been a Japanese snack favorite.

A 75-year-old employee at another shop said he sometimes charges three times the usual price for salmon roe, admitting, "Some customers have told me they'll hold off this season."

Japan's salmon fishing industry, a key driver of the country's food culture, peaked in the 1990s and 2000s as artificial hatching and release programs expanded.

Juvenile salmon, or fry, released in Hokkaido and the northeastern Tohoku region head out to sea in spring, staying in coastal waters until summer. In fall, they migrate north through the Sea of Okhotsk, the Bering Sea and the Gulf of Alaska, where they grow and migrate seasonally before returning to Japan after about four years.

But a crack has emerged in this cycle. According to Kaeriyama, pink salmon, which thrive in colder waters, are rapidly increasing in the Bering Sea in the northern Pacific Ocean due to rising sea temperatures caused by global warming.

Because pink salmon feed on the same nutrient-rich zooplankton as chum salmon, intense competition has ensued, with chum salmon losing the battle for food and struggling to grow, leading to their decline, he said.

With fewer salmon returning to Japan, securing eggs for artificial hatching has been difficult.

An association to promote the breeding of salmon and freshwater trout in Iwate Prefecture in northeastern Japan had received about 40 million of the 60 million eggs hatched in fiscal 2023 from Hokkaido, but due to a shortage of eggs in Hokkaido, the association said it had received none this fiscal year.

But the salmon industry is not standing idly by. Since fiscal 2022, the association has doubled the weight of released fry to about 2 to 3 grams, expecting higher survival rates by allowing them to grow before being released into rivers.

"It will take several years to see the results, but we must do what we can," said an association official.

While Kaeriyama sees potential in these efforts, he warned that without addressing the root cause of global warming, reversing the decline in salmon populations will be difficult.

"I'd urge people to understand that this is not just about the inability to secure fishery resources, but also about the survival of the species itself."