LONDON — When the annual meeting of the International Whaling Commission opened in Alaska last Monday, Japan declared that it planned to kill 50 humpback whales as well as the usual minke and fin whales next year in its “scientific” whale hunt (catch them, count them and sell them as food).

The plan was “highly provocative,” Australian Environment Minister Malcolm Turnbull said. It was also carefully calculated, as Japan’s real goal was to restart commercial whaling. Japan offered to drop the plan to kill humpbacks if the IWC approved a return to “limited commercial whaling” by four Japanese coastal villages — just four little villages, for now, and strictly limited numbers of whales. But the 1986 moratorium on commercial whaling would have been broken.

The pro-moratorium countries at the IWC understood Japan’s tactics and didn’t make the deal, reckoning that the lives of 50 humpbacks were less important than the principle of no commercial whaling. On Thursday, the final day of the meeting, fierce opposition forced Japan to scrap its “community whaling” proposal. The IWC then approved a nonbinding resolution to continue the temporary ban on commercial whaling.

The killing of 50 humpbacks is regrettable, but it will not endanger a species that has gradually recovered to perhaps 60,000 to 70,000 since 1986, when the humpbacks were heading for extinction.

Which is not to say that the humpbacks have really recovered from the carnage of the whaling era. The IWC estimates that there were only 115,000 humpbacks before whaling began, but in a 2005 study marine biologist Steve Palumbi of Stanford University examined genetic diversity among humpbacks, which is directly related to the size of the ancestral population, and concluded that there used to be between 750,000 and 2 million of them. At best, humpback whales have only recovered to 8 percent of their former numbers, and it may be as little as 3 percent.

We care about whales now (call it mammalian solidarity, if you like), but the fish of the oceans benefit from no such sentiment, and they are now going as fast as the whales once were. In fact, according to a report last year in “Nature,” the scientific journal, 90 percent of the really big fish — tuna, marlin, swordfish and the like — are already gone, and the middle-size fish are following.

The codfish are gone on the Grand Banks of Newfoundland, once the richest fishery in the world, and show little sign of recovery despite an absolute ban on cod-fishing for the past 15 years. They are declining rapidly in the North Sea, too. In the 1980s the annual catch was about 300,000 tons. The European Union quota for codfish was cut to 80,000 tons in 2005 — and EU fishermen only managed to catch two-thirds of that quota. Nevertheless, they will probably keep on fishing, with gradually reducing quotas, until the stock is completely eliminated.

The problem is global. As human numbers have soared and fishing technologies have been industrialized, fishing has been mutated from the maritime equivalent of slash-and-burn agriculture to a process more like strip-mining. The schools of fish are located electronically, few individuals escape the huge nets, and no area of the ocean is left alone long enough for the stocks to recover.

“At this point, 29 percent of fish and seafood species have collapsed; that is, their catch has declined by 90 percent,” explained professor Boris Worm of Dalhousie University late last year. “It is a very clear trend, and it is accelerating.” If the trend continues, he predicted, all fish and seafood species that are fished commercially will collapse by 2048.

Individual fishermen, up to their ears in debt for their high-tech boats and equipment, cannot reverse this trend because they have to go on fishing. Governments could cut the huge subsidies they give to their fishermen, and above all to the bottom-trawlers that are systematically turning the floors of the world’s oceans to mud, but they are unwilling to face the political protests of well-organized fishing lobbies. The systematic destruction of the world’s fisheries will continue unless some body equivalent to the International Whaling Commission takes charge, and how likely is that?

Not very. Or at least, an International Fisheries Commission with global regulatory authority is only likely to be accepted, as the IWC was, when all the commercial stocks have already collapsed. Yet fast-breeding fish can recover far faster than whales: As little as five years would allow most fish stocks to recover if a moratorium is imposed before total population collapse occurs. And you don’t have to do it in every area at once; most stocks are quite local.

A major human food source — the principal source of protein for one-fifth of the human race — is going to collapse in the next generation unless drastic measures are taken. The world’s fishing fleet needs to be reduced by at least two-thirds, bottom-trawling must be banned outright, and widespread fishing moratoriums for endangered species and even for whole areas need to be imposed for periods of five or even 10 years.

Unfortunately, the minimum measures needed to prevent ecocide in the oceans would cause major short-term disruption and throw millions out of work, so they probably won’t be taken. It will be much easier politically to ignore what is happening now and let the collapse happen later, on somebody else’s watch.