Yellowtail, Japanese Spanish mackerel moving north

Global warming is raising seawater temperatures off Japan, allowing migratory fish to stay north longer.

A study appearing in the journal Nature last May found that warming ocean temperatures have moved the distribution of fish preferring cold seas farther to the north and into deeper offshore waters, making it likely that reduced quantities of fish will be harvested in low-latitude seas.

In the study, “Signature of ocean warming in global fisheries catch” (Cheung, William et al.), sea surface temperatures and harvest data for 990 fish species in 52 major fishing grounds from 1970 to 2006 were examined to compile an index measuring the proportion of fish preferring warm seas. A consistent trend was found in most of the major fishing grounds that the proportion of fish that prefer warm seas has increased while catches of fish that prefer cold seas has decreased.

In the waters of Japan, Spanish mackerel, sardines and yellowtail around the East China Sea had moved north.

Good catches of Japanese Spanish mackerel off the coast of Chiba prefecture have pushed the wholesale price at Tokyo’s Tsukiji market down 3 to 4 percent from the same period last year, to about 800 yen (USD 7.80,; EUR 5.75) per kilogram (kg). Because of inflation of imported food items due to the weak yen, more retailers are focusing on purchases of Spanish mackerel and yellowtail for grilling. Spanish mackerel are fatty in winter. They are often caught in the Seto Inland Sea and off Kyushu, but unusually large catches are being landed off Chiba Prefecture this year, part of a northward change of distribution for several species from fifth.

Winter yellowtail, called “kanburi” in Japanese, are also popular for grilling, most frequently with a teriyaki favor. They are the same species as farmed yellowtail, but are older, larger and fattier.

At the Kanazawa Central Wholesale Market, the yellowtail season started well, with the first large catch, 820 fish of 6 to 15.9 kg, sold on 6 December at JPY 1400 to 1800 (USD 13.50 to 17.50, EUR 10 to 13) per kg. The number sold reached a record high for the season of 900 at the morning auction on 4 January, the first auction of the New Year. The fish ranged from 6 to 13.8 kg with large fish traded at JPY 2,500 (USD 24.40, EUR 18) per kg. The average daily number of wild yellowtail sold at the market during the season is about 500, with the peak for landings from the start to the middle of January.

In nearby Toyama Prefecture, the migration of fatty winter yellowtail down the Sea of Japan peaked early. Strong early catches and prices of up to JPY 2,500 per kg raised hopes of a good year, but smaller and fewer fish were caught later in the season, so that the total catch through the end of January was at the same level as previous years, at 61,770 fish.

Meanwhile, Hokkaido, Japan’s northernmost island, is having a record harvest, expected to reach 12,000 metric tons (MT). A nationwide heat wave kept seawater temperatures high in Hokkaido. Since the 1990s, the island’s catch of winter yellowtail has tended to increase against the background of global warming.

As for farmed yellowtail, the Japanese government is seeking to restrain production in the coming year. At a meeting with fishing cooperatives, the government announced a goal of a reducing the production volume of amberjack and yellowtail by 140,000 MT, or 10 percent less than the 2012 level, in order to maintain prices and prevent fish farmers from incurring losses. They are asking fishery cooperatives to assist in reducing production.

Unlike the case of tuna farming, for which the government must regulate the scale of aquaculture to protect immature fish, the purpose of this target is just to prevent falling prices due to overproduction. It represents a reversal from the Fishery Agency’s previous goal of expanding aquaculture and runs counter to free market competition at the same time the government is planning to reduce marketing controls and subsidies for rice.