Higher seawater temperatures are causing a shift in the types of fish landed in Hokkaido, Japan.
Landings of cold-water species like salmon, saury, and squid have been decreasing, while catches of warm-water fish like yellowtail have increased.
The national catch of saury – most of which is landed off Hokkaido or Northeast Honshu Island – ranged from around 190,000 to 340,000 metric tons (MT) from 2001 to 2012. Since then, a sharp declining trend brought the catch down to a mere 40,000 MT in 2019.
A 2017 research paper, “Interdecadal decrease in potential fishing areas for Pacific saury off the southeastern coast of Hokkaido, Japan,” examined sea surface temperatures and other variables for 1993 to 2014 off the southeastern coast of Hokkaido for the early fishing season of August through September. Researchers found a higher frequency of termperatures in the warm range of 12 to 18 degrees Celcius from August to September, a trend observed since 2002. This corresponded with a decrease in satellite-based measurements of chlorophyll concentrations for that decade, indicating less algae for saury to feed on.
The paper also noted a change in the direction of the area's major water currents. Typically, cold water from the Okhotsk Sea would enter the Pacific around the Kuril Islands and would carry cold water rich in nutrients and minerals southward along Hokkaido’s eastern coast. Giant eddies of warm water from the Kuroshio Current coming up from the south were pushed offshore. However, in recent years, the cold currents have shifted northward, running straight out to the Pacific, while the warm eddies hug the shore. This puts the saury fishing grounds out of reach of Japan’s shore-based fishermen, and brought the fish instead to international waters outside of Japan’s exclusive economic zone, where Chinese and Taiwanese factory ships have stepped up their activities.
Hokkaido's squid catch is also declining. The amount of Japanese flying squid passing through the Hakodate City Fisheries Regional Wholesale Market in Hokkaido in the season from June to September declined from over 4,000 MT in 2005 to just 275 MT in 2020. Prices, meanwhile, have risen from around JPY 200 (USD 1.92, EUR 1.58) per kilogram to over JPY 800 (USD 7.69, EUR 6.34).
Conversely, catches of yellowtail, a warm-water species, have increased. Data from a Ministry of Agriculture Forestry and Fisheries white paper show that landings in the Hokkaido ranged climbed from 305 MT in 2003 to 3,429 MT in 2005. Moreover, there was a marked increase to 7,146 MT from the year 2011, and in 2013, 12,016 MT of yellowtail were landed. The catch has remained in the higher range, according to the white paper.
It is expected that processors will have to adjust to the new species. Fresh yellowtail doesn’t solve the problem of idle saury canning lines – the production and the equipment required are not the same. And it is not expected that the value will fully offset the loss of saury and squid.
Photo courtesy of Chris Loew/SeafoodSource
