Higher sea temperature impacts Japan's autumn sea delicacies

Autumn is the time when people in Japan enjoy seafood such as saury, bonito, mackerel and salmon, but the seasonal catch is not what it used to be.

This season's first auction of blowfish was held Monday in the western Japanese city of Shimonoseki, heralding the arrival of the traditional delicacy on the market.

The Haedomari fish market in Shimonoseki handles the largest volume of the wild torafugu variety in Japan.

But Monday's blowfish catch was around one-third of the seasonal average. The highest price was 22,000 yen, or roughly 150 dollars, per kilogram, which was 40 dollars higher than last year.

The president of a local fish dealer, Goda Yuichiro, attributes the loss to higher sea temperatures.

"The ocean temperatures are very much higher than usual, so the blowfish aren't coming in toward the shore," he says.

Warmer ocean hits kelp farmers

Kelp farmers in Hakodate City in the northern prefecture of Hokkaido are worried that their popular konbu kelp may not be up to par.

Marine creatures known as hydrozoa – in the same family as jellyfish and sea anemones – cling to the kelp.

Hakodate's konbu kelp is popular in Japan as a luxury food product.

Hakodate officials say eating kelp that have hydrozoa poses no health risks, but distributors have been removing the portions with the hydrozoa for better appearance, so the harvest volume has shrunk.

The extra work also causes shipment delays of around one month compared to normal years.

"This is what happens when ocean temperatures rise," bemoans local kelp farmer Yoshida Tetsuro.

Yoshida Tetsuro has been a kelp farmer for over half a century.

Sea surface temperatures hit record high

Japan's Meteorological Agency reported that the average sea surface temperatures around the country in August were one degree warmer than usual. That's the highest since record-keeping began in 1982.

The map shows how much hotter the ocean surface was in August this year compared to average years. The darker the red, the higher the temperature.

EU and UN meteorological agencies reported that global sea surface temperatures averaged 20.98 degrees in August, also a record for all months. The previous record was logged in March 2016.

Nishida Hiroshi, head of the Japan Fisheries Research and Education Agency, says there is "an appropriate temperature" which is conducive for each kind of fish to grow and to live.

"When that temperature changes, or if the temperature change results in the distribution of microscopic and miniscule organisms that did not previously exist at that area at that season, then the animals the fish used to feed on might disappear, or their distribution might change," Nishida explains.

"As a result, the fish that people expect at a certain season would not be available at that time, or the fish would disappear altogether from that area."

Nishida Hiroshi, head of the Japan Fisheries Research and Education Agency, says the temperature change could alter the environment for fish.