STANFORD (US)—Five out of 10 global ecosystems once threatened by overfishing are on the mend, suggesting fishery restrictions “can actually pay off and things can get better,” says study collaborator Stephen Palumbi.
An international team of scientists analyzed fish populations around the world and found that the mass of fish removed from the ocean every year has decreased in some fisheries. Their findings appear in the July 31 issue of Science.
“This improvement might well be a reflection of the call to arms that has gone out over the last five to 10 years about the state of the ocean and its needs,” says Palumbi, professor of biology and director of the Hopkins Marine Station at Stanford University and senior fellow at the Woods Institute for the Environment.
The researchers warn, however, that a promising global average based on the 10 studied ecosystems may hide regional variation.
“These 10 ecosystems really are the elite fisheries of the world—the ones with the most funding, the most research, and the most enforcement,” Palumbi explains.
Recovery of fish stocks in a developing country, on the other hand, is challenging when locals lack alternative sources of food, income, and employment.
The five ecosystems in which fishing rates have dropped to at least a healthy level called maximum sustainable yield include oceans surrounding New Zealand; northwestern Australia; Iceland; the California current system stretching from Baja California to Canada; and western Canada and Alaska, up to the Bering Strait. Maximum sustainable yield is the greatest amount of fish that can be harvested without depleting the population in the long term.
For the study, the group used ecosystem models to analyze records of global catches, small-scale fishery data, trawl surveys and stock assessments, which show the status of exploited fish populations.
Not all of their findings were good news—out of 166 fish stocks, 63 percent had collapsed. The ecosystems which remain in decline include oceans surrounding southeastern Australia, the Gulf of Thailand, northern Europe, northeastern United States, and eastern Canada.
The new study was actually initiated by a disagreement between two groups of scientists. University of Washington fisheries scientist Ray Hilborn questioned methods used by a different group led by Boris Worm of Dalhousie University in Canada, which predicted in 2006 that most harvested fish species would collapse by 2048. Because the debate opened areas of common ground, the two began meeting to discuss their findings and eventually launch the new study.
If a lower rate of harvesting is enforced, the scientists say, the recovery of these ecosystems may be possible. Catch restrictions, closing areas and implementing economic incentives including sustainable fishery certification, will help in this effort.
Such attempts were successful in Kenya where fish populations living in coral reefs recovered after local communities closed areas and restricted fishing gear such as beach seines, which catch unwanted marine animals along with the target fish. Fish size and weight improved, leading to steep increases in fishers’ incomes.
The scientists also suggest joining forces of fishery management and conservation through marine protection acts.
“The two together—well managed fisheries and marine protected areas—are likely to be great partners in rebuilding marine ecosystems,” Palumbi says. “They’re different strategies but they’re quite complementary.”
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