Efforts to protect salmon on North America's Pacific coast could take a lesson from investors who hold diversified stock portfolios, according to a study published on Wednesday.
Maintaining diversification within the salmon population will buffer the commercial fishery from the turmoil caused by the yearly ups and downs of individual fish runs, the U.S. researchers reported.
"It's the diversity of the mix that provides stability .... Anyone who has put all of their money on the hot stock, be that Enron or the Florida real estate market, has learned that lesson," said Ray Hilborn of the University of Washington.
Some salmon do better in cold wet years, while others thrive in hot dry years, with that diversity -- even within species -- bred into them by variations such as what coastal waterway they spawned in.
Species of salmon in the Pacific include sockeye, pink, coho, chinook and chum. They are born in fresh water, spend their adult lives in the saltwater ocean, but return to their natal rivers or lakes to spawn and die.
The study published in the journal Nature challenges salmon management theories in the United States and Canada that are based on protecting the total number of a salmon species that return to the coast each year to spawn.
"The game-changing part is we start thinking not about how many fish we have coming back, but on the diversity of fish we have coming back," Hilborn said in a telephone briefing.
The researchers studied five decades of data on sockeye salmon in Alaska's Bristol Bay, where they credit diversification within the sockeye population with keeping that fishery healthier than many others on the U.S. and Canadian coasts.
Once-thriving fisheries in California and Washington state have seen the diversity of their salmon decline because of heavy fishing, loss of spawning habitat and use of hatcheries to bolster the wild population.
Large hatcheries homogenize the salmon population in areas they serve, which makes the populations more vulnerable to problems like disease and the impact of climate change, according to the researchers.
The researchers said protecting diversity will require protecting the varied spawning habitats, but it should help the salmon recover in areas where they have been depleted and to adapt to climate change.
"They have a remarkable ability to evolve and adapt to new conditions," said the University of Washington's Daniel Schindler, who spoke to reporters from Alaska.
ReutersLast Mod: 02 Haziran 2010, 20:39