Photo/Illutration Freshly caught saury at Hanasaki port in Hokkaido’s Nemuro in August (Tomoyuki Yamamoto)

Poor saury catches continue while the fish keep shrinking in size as global warming hammers the traditional autumn delicacy in Japan, researchers say.

The nationwide haul of saury, or “sanma,” has hit record lows for four straight years, including 17,910 tons last year.

According to the Japan saury stick held dip net fisheries cooperative association, 15,471 tons of saury had been caught this year by the end of October. Although that is 40 percent higher than the haul for same period last year, the yield is still described as low.

At one time, 200,000 to 300,000 tons of saury were caught nationwide annually.

At markets near fishing grounds, saury were being sold for 4,893 yen ($32) per 10 kilograms at the end of October, triple the cost in the same period in 2010.

Salted and grilled fatty sanma with a plump section on the back of the head are especially tasty.

However, many supermarkets these days can offer only small thin saury.

“Saury have obviously become smaller lately,” said Kazuyoshi Watanabe, head of the fishing data department of the Japan Fisheries Information Service Center. “Although 160-gram-plus saury used to be common, such fish are now rarely reported.”

According to the center’s surveys, saury of 160 grams or over accounted for nearly half of all saury caught on one day in late September 2014 off Hanasaki port in Hokkaido’s Nemuro. This haul included an “extra-large” sanma weighing 200 grams.

In the one-day survey in late September this year off the same port, the larger saury among the catch were around 140 grams.

Studies off eastern Hokkaido every September by the Kushiro Fisheries Research Institute of the Hokkaido Research Organization also underscore the increasing thinness of saury.

“Tiny saury that had previously been turned into processed products have lately been delivered fresh to consumers,” said Ryotaro Ishida, a senior researcher at the institute. “Consumers can now more easily see that the fish’s body has become smaller.”

Sanma’s fatness level has been declining since 2012, according to institute’s parameters on their “chunkiness.”

The problem, according to Watanabe, is a change in the fish’s basic life cycle.

Saury normally migrate to cold northern waters for abundant food sources from spring to summer. They travel southward along the chilly Oyashio current in autumn to lay eggs.

However, the shrinking saury population has led to fewer schools heading northward off the Japanese archipelago for nutrients.

Watanabe also said the prolonged hot seawater associated with marine heatwaves and other elements have pushed down zooplankton volumes. The decrease has made it difficult for saury to gain fat.

Another problem for saury is that sardines have proliferated this season, and the two variants compete for habitats and prey.

SPECIALTY IN WINTER, NOT AUTUMN

Global warming could dramatically exacerbate the fate of saury, said Shinichi Ito, a fisheries oceanography professor at the Atmosphere and Ocean Research Institute of the University of Tokyo.

Ito has studied the environmental impact on sanma based on climate change scenarios released by the Intergovernmental Panel on Climate Change (IPCC).

His computerized simulation indicates that if global warming continues at its current pace, saury by the end of this century will be 2.5 centimeters shorter and 40 grams lighter than the averages up until the 1990s.

Ito said a plankton shortage will lead to the saury shrinkages.

Global warming will cause sea surface temperatures to remain high even after the arrival of winter, according to the simulation. This can weaken circulation between shallow and deep waters, and an insufficient amount of nutrients would reach the surface for plankton.

“Saury are growing thinner much faster than I expected,” Ito said.

His simulation also showed that saury may head southward later in the year to lay eggs. That could postpone the prime fishing season for the fish from fall to winter.

“I feel lonely if saury are no longer available as an autumn delicacy,” Ito said.

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