A new U.S. study on sockeye shows the salmon fishing strategy for British Columbia needs to be reorganized to do a better job of protecting weak stocks, rather than on maximizing the catch when runs are large, salmon experts say.
"I think it has huge implications to our current sockeye situation," Craig Orr, executive director of Watershed Watch Salmon Society, said in reaction to a research paper released Wednesday by the University of Washington.
The study found the key to maintaining healthy salmon stocks over time lies in ensuring there is a wide diversity of stocks within a given species.
The researchers looked at Bristol Bay, Alaska, where the annual run of 30 million sockeye has remained stable since 1950 because of a harvest strategy that ensures weak stocks are protected, while maximizing the commercial catch. During that same period, sockeye runs in B.C. rivers, such as the Fraser and Skeena, have gone through dramatic ups and downs.
Mr. Orr said the problem in British Columbia has been that fisheries target big runs of salmon where many stocks are mixed together. The result has been an erosion of the smaller stocks, which diminishes the population diversity the Alaska study found to be so important.
"The … paper clearly shows that our best bet for maintaining both Fraser sockeye productivity and fishing opportunities for Fraser sockeye is to manage for diversity," Mr. Orr said.
"Right now we tend to base fisheries on the strength of one or two dominant runs … and we are prepared to fish those runs hard, even if it means overfishing less productive stocks, sometimes to the very brink of extirpation."
Jeffery Young, an aquatic biologist with the David Suzuki Foundation, agrees.
"We've always known that protecting biodiversity is a key element of keeping ecosystems functioning … what this study homes in on is how true that is for salmon," Mr. Young said.
"The main thing right now is to acknowledge we are in a difficult spot for sockeye … we are starting to lose diversity," he said.
But Phil Eidsvik, a spokesman for the B.C. Fisheries Survival Coalition, a group representing a broad cross section of commercial fishermen, said managing blindly to protect weak stocks can do more damage than good.
Mr. Eidsvik said "you can depress small runs by allowing too many fish through" because the larger populations swamp the weaker stocks on the spawning grounds.
"Our approach over the years has been a lot different than Alaska's," he said. "In our attempt to protect small stocks we have allowed larger populations to become extremely dominant … when you put huge amounts [of one population] on the spawning grounds you make some [weaker]stocks crash."
Mr. Eidsvik commented before he had a chance to read the research paper.
"But there's a lot to be learned from Alaska, that's for sure," he said. "They have managed their salmon differently. The Alaska model has been successful. The B.C. model hasn't."
He said Alaska manages for a maximum sustained yield, after ensuring a predetermined number of salmon have been allowed to escape commercial harvest to spawn. He said in British Columbia fishing closures are often imposed in a way that allows too many of one population to spawn.
Mr. Eidsvik said he hopes a new direction in fisheries management emerges from a federal judicial inquiry into the Fraser River sockeye, which is to begin public hearings later this year.
While salmon fishing was banned in many areas of British Columbia last year because of poor runs, the Bristol Bay area had another good year, with the commercial fleet hauling in a catch worth $120-million (U.S.).
"Bristol Bay is a well-known example of a sustainable fishery where sockeye salmon have been caught in huge numbers reliably, year after year, since the first canneries were built in the late 1800s," said Daniel Schindler, lead author of the study, which appears on the cover of the science journal Nature.
"In the last 50 years, this fishery has produced more than $5-billion [worth] of salmon, making it one of the single most valuable fisheries in North America. Our study helps explain why the Bristol Bay sockeye fishery has been so reliable for so long," he said in an interview from a field camp in Aleknagik, southwest Alaska.
Dr. Schindler said Bristol Bay is steadily productive because there are so many different types of sockeye there.
He said having many different populations of salmon is like having a diversified stock portfolio, in which strong performers compensate for weak ones, smoothing out the bumps.
"Our study shows that the 'portfolio effect' is caused by small differences in how different populations of sockeye salmon respond to their environment. Some populations perform better in cold, wet years while others thrive while it's hot or dry," Dr. Schindler said.
He said when stocks become homogenized - as they do when hatcheries produce huge numbers of fish or development destroys a range of habitat - the result can be boom or bust cycles.
"We believe this new evidence from our Bristol Bay salmon study is a game changer for managing species and entire ecosystems because the lessons from this paper result in specific advice for natural resource management," said co-author, Ray Hilborn.
In British Columbia the federal Department of Fisheries and Oceans in 2008 adopted a wild salmon policy that stresses protecting diversity. DFO officials were unavailable for comment.