This is the VOA Special English Agriculture Report.

Too much fishing has reduced many fishery populations by ninety percent or more from their highest recorded numbers. Some fishing seasons last only a few days because the catch limit is quickly reached.

Two years ago, a Canadian scientist, Boris Worm, predicted the risk of a worldwide fishery collapse by two thousand forty-eight. But a new study says a management system called "catch shares" could offer a solution.

It divides the total permitted catch in a fishery into shares. These are bought and sold like shares of stock in a company. Shareholders in the fishery are each guaranteed a percentage of the catch.

Catch share systems are common in Australia, New Zealand and Iceland. And they have been gaining popularity in the United States and Canada.

Systems differ from place to place. But in general, experts set yearly limits, or quotas, on a fishery. The number of fish that each company or individual may catch is usually based on past averages.

Shares become more valuable as fish populations increase. With more fish in the fishery, catch limits also increase.

Human nature would tell us that shareholders are more likely to think about the long-term health of the fishery. They have a greater interest to protect the supply than in traditional, open access fisheries. But does that really happen?

Researchers looked at more than fifty years of records from eleven thousand fisheries worldwide. They compared open access fisheries with one hundred twenty-one fisheries that use catch share systems.

The study found that almost a third of the traditional fisheries have collapsed. But the number was only half that for the catch share fisheries. The findings appeared this month in the journal Science.

Researchers from the University of California, Santa Barbara, and the University of Hawaii did the study. The economist who led the research, Christopher Costello at Santa Barbara, called the results very hopeful. He says the system can improve the world's fishing grounds and rebuild collapsed fisheries.

Still, not everyone likes the idea. Some environmental activists say the catch share system makes a public resource into a private enterprise. Generally speaking, anybody can work a traditional fishery. There is no need to organize into a group or company. Yet if scientists' warnings are correct, those fisheries may not have many fish left to catch by the middle of the century.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. I'm Bob Doughty.