Warming waters and red tide plague Japan’s northeast fisheries

Cold-water fish that have been the mainstay for fishers and processors in Japan’s northeast are becoming increasingly scarce as sea-water temperatures in the region rise.

The Pacific coast of Hokkaido and the Sanriku coast – which includes parts of Aomori, Iwate, and Miyagi prefectures – have been affected the worse by rising seawater temperatures, which are keeping schools of cold-water fish further off the coast.

This year’s Pacific saury quota for Japan is a record low of 155,335 metric tons (MT), down 41.2 percent from 2020. Japan’s 2021 quota was set in line with an-across-the-board catch reduction agreed with China, Taiwan, Russia, and other members of the North Pacific Fisheries Commission. However, it is unlikely that the country will get close to the quota – last year the country caught just 29,562 MT, the second year for record-low landings.

A spreadsheet from the commission's meeting, “Summary Footprint of Pacific Saury Fisheries,” gives a picture of the recent drops in catch. In 2010, Japan landed 207,489 MT of Pacific saury – a fairly average number at the time. South Korea landed 21,360 MT, Russia caught 31,686 MT, and Taiwan caught 165,692 MT, for a total of 426,227 MT.

In 2020, China and the Pacific island country of Vanuatu are now members of the fishery, hauling up 44,006 MT and 2,700 MT, respectively. Japan caught 29,562 MT, South Korea brought in 5,993 MT, and Russia landed just 753 MT out of a total 83,014 MT of Pacific saury landed.

The 2020 Japanese flying squid quota was also the lowest ever, at 57,000 MT. High water temperatures in the East China Sea, making conditions unfavorable for the squid to lay eggs, were blamed. As squid have a one-year lifespan, the conditions in their spawning grounds are the most-important factor in recruitment, scientists have found.

Chum salmon was also affected water conditions that could be changing due to climate change. A red tide off the Pacific coast of Hokkaido, which occurred from 5 to 13 October, killed a large number of chum salmon and sea urchin.

More broadly, salmon populations have been in decline in Japan, with catches plummeting by nearly 70 percent in the last decade, despite one of the world’s largest supplemental hatchery programs.

The North Pacific Anadromous Fish Commission's Preliminary Statistics for 2020 Commercial Salmon Catches in Japan showed catches totaling 21.6 million fish, including 17.5 million chum and 4.1 million pinks. This is down around 50 percent compared with a decade earlier, when total commercial catches of salmon in coastal and offshore areas of Japan were more than double, at 54.1 million fish, including 45.2 million chum and 8.9 million pinks, according to Japan Salmon Commercial Fisheries Catch Statistics for 2010.

The cause may be a reduction in the amount of oxygen, iron, and other key nutrients produced in the Sea of Okhotsk through sea ice formation. The coldest parts of this sea have seen a sea-water temperature increase of over three degrees, far more than the global average of about 1.2 degrees Celsius.  

Photo courtesy of GUDKOV ANDREY/Shutterstock