Japan’s Fisheries Agency has announced a proposal to halve the annual catch of immature Pacific bluefin tuna. The proposal is expected to be officially adopted at a December meeting of the Western and Central Pacific Fisheries Commission, established in 2004 to conserve and manage fish stocks.

Unfortunately the commission has not yet done enough to ensure sustainable and healthy fish populations. The proposal, even if it is adopted, may be too little too late.

The commission’s membership includes nearly every country in the north Pacific, so the proposal is an important one if people in Japan and around the world want to continue eating tuna.

Already, Bigeye and Pacific bluefin tuna, as well as many shark species, have been overfished. The waters managed by the WCPFC cover almost 20 percent of the Earth’s surface and provide more than half of the world’s tuna, 70 percent of which reportedly goes to Japan.

An assessment in 2013 by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean, an independent group of scientists, found that the Pacific bluefin population is now at 4 percent of its historical size. Because 96 percent of the population is already gone, nearly all the Pacific bluefin tuna caught today have not had a chance to grow to full size or value. Nor have most reproduced. The tipping point toward extinction may be soon.

The popularity of Pacific bluefin tuna in Japan, especially for sushi and sashimi, has been one factor in overfishing. The popular fish are also victims of illegal, unreported and unregulated fishing in many areas of the Pacific. Currently there are no scientifically researched catch limits for Pacific bluefin tuna.

Japan’s annual limit must be reduced enough to allow sustainability. That relates not only to weight limits but also to reducing purse seine fishing, as well as fishing with fixed shore nets closer to coastal areas.

Japan should help to establish limits on all types of fishing on the basis of scientific research and convince other countries to accept the same. Japan can help maintain a system that issues advisories when limits are approached, and to issue calls for restraint so limits are not inadvertently exceeded.

More importantly perhaps, all countries need to agree to limit fish size. That would cause difficulty to the fishing industry, but there is no other way to allow the Pacific bluefin tuna to reach maturity and have a chance to reproduce. Without such careful conservation, the Pacific stocks will have little chance of recovering or returning to higher levels.

Because the tuna are one of the ocean’s top predators, their reduction threatens to unbalance the entire ecosystem. Japan should move forward with its proposal, and strengthen it, before it is too late.

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