Eat This Newsletter 244: Tuna
Hello
Only one story this week, and an optimistic one at that.
Tuna Bounce Back
Bluefin tuna in the Pacific passed a significant milestone on their road to recovery 10 years ahead of schedule. That’s the story in front of the joint meeting of the Inter-American Tropical Tuna Commission and the Western and Central Pacific Fisheries Commission, which kicked off in Hokkaido last week. Before I cheer too loudly, though, I want to be reassured that the good news won’t immediately be welcomed with higher quotas, which would be not be unexpected.
Pacific bluefin tuna (henceforth, tuna) were in big trouble a decade or so ago. Overfishing in the 1990s and early 2000s had reduced the stock of breeding adults to around 2% of what it would have been in the absence of fishing. Negotiations in 2011 established a recovery plan, the key element of which was a reduction in quotas, with an expectation that the stock would recover to at least 20% of its unfished size by 2035. In June, the international scientific committee that provides data to the decision makers announced that the stock reached 23.2% of its unfished value in 2022, above the maximum sustainable yield for the first time.
In some respects, the very rapid population increase is not surprising. An adult female tuna can lay millions of eggs, not many of which have to survive to adulthood themselves to make a huge difference to the stock. The worry now is that the stock recovery will tempt government decision makers to demand changes to the quotas that enabled the recovery.
Japan Does Not Disappoint
Unsurprisingly, Japan’s Minister of Agriculture, Forestry and Fisheries did just that in a video address to the meeting. “It is necessary to increase the quotas to reflect the current situation of tuna stocks,” he said.
It is not clear (to me) why bigger stocks make it necessary, rather than desirable, for the Japanese tuna fish industry to snag bigger quotas. Currently Japan takes 74% of the quota for adult tuna (larger than 30 kg) and 85% of the smaller fish. Quotas were increased by 15% in 2022 after the tuna population started to recover. Now, Japan wants to more than double the quota on adult fish and increase the juvenile quota by almost a third. A final decision is expected by Tuesday 16 July.
One flaw with quotas is that even when they are allocated to individual boats, they can be exceeded because boats are seldom in contact with one another, so they do not know how the fleet as a whole is doing. Tuna in excess of the total quota can thus still be caught and killed, although boats may be fined for their extra haul. Some efforts have been made to enable boats to transfer quota among themselves, so a successful boat can buy quota from a boat with some to spare, but this system is not yet operating very effectively.
And now
There are other problems facing the tuna fishery, most notably changes in the migration routes of the tuna caused by the climate emergency. The models have not yet been applied to bluefin, but for other tuna species predict that they will move east and north. This could spell trouble for Pacific Island States, many of which sell access to their fisheries to vessels from other countries. These access fees average almost 40% of government revenues for the 10 most westerly states. Japan’s ocean-going boats will probably be able to follow the tuna wherever they go, if they can get access. Mexico, currently second to Japan, may benefit even more.
For me, the real lesson here is that biologists do know how to model and predict population changes under different levels of pressure, and if those applying the pressure are prepared to listen, results are usually good. Trouble is, they’re not usually prepared to listen.
Take care
p.s. That article on climate change and migration is presented in a format that is nothing short of appalling. I forced myself through it so you don’t have to, although I will concede that it does a good job of explaining some of the basic science. You have been warned.
p.p.s. If you do not recall seeing that astonishing tuna photograph, from Tom Benson on flickr, you might want to go and listen to the episode on Fully Tested Tuna with Sean Wittenberg.