Stocks of Pacific bluefin tuna, which this nation consumes in large quantities — equivalent to 80 percent of the world’s total catch — are now critically low and no optimism is warranted for their recovery. The Fisheries Agency is introducing a new system to control catches, but it needs to make serious efforts to ensure that its steps will be effective in restoring Pacific bluefin stocks. The agency will face severe criticism not only from domestic fishermen but also from the international community concerned with conservation of the species if the new steps fail to bring about tangible results.

In 2014, the International Union of Conservation of Nature put the Pacific bluefin tuna on its list of threatened species, warning that its population has declined between 19 and 33 percent over the past 22 years and that the condition of the stock is unlikely to improve since the number of new fish added to the fishable population each year, a process known as “recruitment,” is low. The annual catch has declined to as low as 15,000 tons from its 1981 peak of 35,000 tons in the Pacific Ocean.

According to an assessment released in April by the International Scientific Committee of Tuna and Tuna-like Species in the North Pacific Ocean (ISC), the Pacific bluefin tuna population has fallen to just 2.6 percent of its population before large-scale commercial fishing started. The total stock of mature fish that can spawn stood at 16,557 tons in 2014, down 90 percent from 160,005 tons in 1961, though slightly up from 13,795 tons in 2012. The ISC pointed out that the population was less than a third of the level just 20 years earlier and estimated that there were approximately 110,000 adult Pacific bluefin tuna remaining in the entire Pacific Ocean.

As another worrisome finding, the committee said that 97.6 percent of all Pacific bluefin tuna caught are immature, which is defined as less than 3 years old. It said that in 2014, the number of recruits less than a year old entering the fishable population was the lowest since 1952 and that the average number of such fish for the last five years was likely below the historical average level.

Pacific bluefin tuna return to areas near Japan — the Sea of Japan and the sea off the Nansei Islands — for spawning after spending a few years near the west coast of the Americas. It takes three to five years for the fish to mature and reach spawning age. The number of recruits in the Sea of Japan in 2014 was 77 percent lower than in 2013, according to Japanese research. Although there was a slight increase in 2015, the figure is still near the historic low.

The Fisheries Agency earlier had a plan to restore the stock of mature Pacific bluefin tuna to 43,000 tons, a historical median, by 2024. But the ISC’s dismal report prompted the agency to revise the plan to reduce the target to 38,000 tons.

The agency’s original plan was based on the measure adopted by the Western and Central Pacific Fisheries Commission (WCPFC) to halve the catch of immature tuna weighing less than 30 kg from the average catch in the base years of 2002 to 2004, starting in 2015. But the WCPFC’s control measure itself is seen as too weak to have a desirable impact on the tuna stock. Since the measure uses the relatively good harvest in the 2002-2004 period as the basis, it will effectively not result in reducing the catch of immature fish from the levels of more recent years. The WCPFC imposes no obligation for cuts in the haul of mature fish, either.

As part of its plan to restore the stock, the Fisheries Agency has introduced a new system to control the Pacific bluefin tuna catch. Previously, the agency had divided the sea around Japan into six blocs — the northern and western parts of the Sea of Japan, the northern and southern parts of the Pacific Ocean, the Seto Inland Sea and the sea west of Kyushu — and placed an upper limit on the catch in each zone. The new system sets prefecture-by-prefecture catch quotas, and will issue a warning when the catch in a prefecture nears the limit.

While the new steps may not be meaningless, the agency should heed fishermen’s concerns that its policy is not strict enough to restore the Pacific bluefin tuna stocks to sustainable levels. Last year, local coastal fishermen in the cities of Iki and Tsushima in Nagasaki Prefecture launched a three-year voluntary ban on catching mature fish in the months of June and July, the period in which they spawn. The agency should realize that the fishermen’s move — which means reduced income for them — testifies to their grave worries about the condition of the tuna stocks.

The coastal fishermen’s move also represents their resentment and opposition to the large fishing operators that use round-haul seines to catch large quantities of Pacific bluefin tuna that have gathered in the waters around Japan for spawning. But the Fisheries Agency is reluctant to restrict the taking of mature tuna — on the grounds that restricting the catch of immature fish is a much more effective way to restore Pacific bluefin tuna stocks.

Yet, it is hard to imagine that allowing large catches of mature fish that are spawning will not lead to a fall in recruitment and the eventual collapse of tuna stocks. The Fisheries Agency’s policy stance should be scrutinized by scientists and other experts.