By Alister Doyle
OSLO (Reuters) - Swift action is required to save many of the world's fisheries that are declining faster than expected, a study in a leading scientific journal shows.
A recovery of fisheries could increase worldwide landings by up to 40 percent, helping to feed a global human population that is forecast to rise from 7 billion to 9 billion between now and 2050, according to the report in Friday's edition of Science.
Coastal fisheries and sharks are among those hardest hit by overfishing, while flounder, herring and sardine are suffering less, the scientists wrote in the journal run by the American Association for the Advancement of Science.
The study focused on the world's "unassessed" fisheries - those that lack good data about the size of stocks. Unassessed fisheries make up 80 percent of the global catch and the vast majority of the world's 10,000 fisheries, the authors said.
"Small-scale unassessed fisheries are in substantially worse shape than was previously thought," Christopher Costello, lead author of the study at the University of California, Santa Barbara, told a telephone news conference.
"The good news here is that it's not too late," he said. "These fisheries can rebound. But the longer we wait, the harder and more costly it will be ... In another ten years, the window of opportunity may have closed."
Unassessed fisheries are declining worldwide and are in a worse condition than their assessed counterparts, the study found. Many well-studied fisheries in developed nations have been recovering in recent years thanks to better management.
One way to promote recovery is to grant communities or individual fishermen exclusive rights to catches in return for respecting "no take" zones. These could be around coral reefs or mangrove swamps that are nurseries for fish, experts said.
"The silver lining is that we have proven solutions," Michael Arbuckle, senior fisheries specialist at the World Bank, told the news conference. "Ending open access in favor of fishing rights is the key."
Other steps to avert collapse include more assessments of fisheries, typically costing $500,000 each, to help to set quotas.
"The revolution here is to empower fishermen to lead the way in recovering fish populations," said Amanda Leland, of the Environmental Defense Fund.
Among signs of recovery, U.S. landings of fish and shellfish hit a 17-year high in 2011, the U.S. National Oceanic and Atmospheric Administration said. The landings were worth $5.3 billion.
In general, Costello said that unassessed fisheries with slow-maturing fish such as sharks were worse off than small, short-lived fish such as anchovies or herring, which could rebound quickly.
The report used data from well-studied fisheries to infer the condition of similar but unassessed fisheries.
Costello said that "the biggest scientific hurdle" had been to ensure confidence that the data were accurate when the fisheries were unassessed.
"Without good information on fish populations, managing (fisheries) sustainably can be a hard thing to do. It's like trying to decide how far you can drive your car without knowing how much gas is in the tank," he said.
(Editing by David Goodman)