FIRST, THE bad news: The world’s fisheries, which feed billions of people, are in serious decline. The authors of a study released Monday in the Proceedings of the National Academy of Sciences examined 4,713 fisheries, accounting for 78 percent of the world’s annual catch, and found that only a third were in decent biological shape.

But there is good news: It is possible to reverse this trend, and in a surprisingly short amount of time.

The underlying problem is that, while the fishing industry as a whole has an interest in sustaining the fisheries that provide it profits and feed the world, individual fishermen have an incentive to take as much as they can as quickly as they can. Over time, they degrade the fisheries on which they rely, but if they want to stay in business, they have little choice. This is a classic instance in which government should step in and regulate the market to prevent the wanton and unnecessary destruction of precious natural resources.

In fact, the researchers reported that governments have extremely effective policy options to eliminate this tragedy of the commons. If applied globally, modern management plans could rehabilitate the median fishery in less than a decade. By 2050, nearly every fishery on the planet would be healthy. The resulting benefits would be astonishing. Relative to business as usual, the refreshed catch would grow by an annual 16 million metric tons, and seafood stocks would rise by 619 million metric tons. Fishermen would see an annual $53 billion rise in profit, a jump of 64 percent. The world’s fisheries could feed more people, and the fishing industry could boom, too.

To bring about this happy ending, governments must give fishermen a stake in the overall health of their fisheries. One way to accomplish this is to require fishermen to hold rights to catch a certain amount of seafood in a certain fishery, which allows governments to manage the total haul and reduces the frenzied competition to scoop up as much as possible as quickly as possible. Ideally, these “catch shares” could be bought and sold so that rights would end up with those who could fish most efficiently.

There may be short-term transition costs; as fishermen pull back to allow fisheries to restock, fisherman could lose money for a time. During that same period, food prices could rise, though the researchers did not model consumer costs.

Yet governments can manage even these drawbacks by imposing a gradual transition rather than shock therapy. All the more reason, though, to act soon, while fisheries still have a chance to recover.