Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Salmon Runs Boom, Go Bust Over Centuries

17.01.2013
Salmon runs are notoriously variable: strong one year, and weak the next. New research shows that the same may be true from one century to the next.

Scientists in the past 20 years have recognized that salmon stocks vary not only year to year, but also on decades-long time cycles. One example is the 30-year to 80-year booms and busts in salmon runs in Alaska and on the West Coast driven by the climate pattern known as the Pacific Decadal Oscillation.

Now work led by University of Washington researchers reveals those decadal cycles may overlay even more important, centuries-long conditions, or regimes, that influence fish productivity. Cycles lasting up to 200 years were found while examining 500-year records of salmon abundance in Southwest Alaska. Natural variations in the abundance of spawning salmon are as large those due to human harvest.

“We’ve been able to reconstruct what salmon runs looked like before the start of commercial fishing. But rather than finding a flat baseline – some sort of long-term average run size – we’ve found that salmon runs fluctuated hugely, even before commercial fishing started. That these strong or weak periods could persist for sometimes hundreds of years means we need to reconsider what we think of as ‘normal’ for salmon stocks,” said Lauren Rogers, who did this work while earning her doctorate in aquatic and fishery sciences at the UW and is now a post-doctoral researcher with the University of Oslo, Norway.

Rogers is the lead author of a paper on the findings in the Jan. 14 online early edition of the Proceedings of the National Academy of Sciences.

“Surprisingly, salmon populations in the same regions do not all show the same changes through time. It is clear that the salmon returning to different rivers march to the beat of a different – slow – drummer,” said Daniel Schindler, UW professor of aquatic and fishery sciences and co-author of the paper.

“The implications for management are profound,” Schindler said. “While it is convenient to assume that ecosystems have a constant static capacity for producing fish, or any natural resource, our data demonstrate clearly that capacity is anything but stationary. Thus, management must be ready to reduce harvesting when ecosystems become unexpectedly less productive and allow increased harvesting when ecosystems shift to more productive regimes.

“Management should also allow, and probably even encourage, fishers to move among rivers to exploit salmon populations that are particularly productive. It is not realistic to assume that all rivers in a region will perform equally well or poorly all the time,” he said.

The researchers examined sediment cores collected from 20 sockeye nursery lakes within 16 major watersheds in southwestern Alaska, including those of Bristol Bay. The scientists homed in on the isotopic signature of nitrogen that salmon accumulate in the ocean and leave behind in lake sediments when they die: When there was a lot of such nitrogen in the sediments, it meant returning runs during that time period were abundant; when there was little, runs had declined.

Climate is not the only reason for long-term changes in salmon abundance. Changes in food webs, diseases or other factors might be involved; however, at present, there are no clear explanations for the factors that cause the long-term variability observed in this study.

Most, but not all, of the lakes examined showed declines in the kind of nitrogen the scientists were tracking beginning around 1900, once commercial fisheries had developed. However, earlier fluctuations showed that natural processes had at times reduced salmon densities as much as recent commercial fisheries, the co-authors said.

“We expected to detect a signal of commercial fishing – fisheries remove a lot of the salmon, and thus salmon nitrogen, that would have otherwise ended up in the sediments. But we were surprised to find that previous returns of salmon to rivers varied just as dramatically,” Rogers said.

As the paper said, “Interestingly these same fluctuations also highlight that salmon stocks have the capacity to rebuild naturally following prolonged periods with low densities, suggesting a strong resilience of salmon to natural and anthropogenic depletion processes. Indeed, total salmon production (catch plus escapements) has been relatively high in recent years for most sockeye salmon stocks in southwestern Alaska, despite a century of intense harvesting.”

Other co-authors are Peter Lisi and Gordon Holtgrieve with the UW, Peter Leavitt and Lynda Bunting with University of Regina, Canada, Bruce Finney with Idaho State University, Daniel Selbie with Fisheries and Oceans Canada, Canada, Guangjie Chen with Yunnan Normal University, China, Irene Gregory-Eaves with McGill University, Canada, and Mark Lisac and Patrick Walsh with Togiak National Wildlife Refuge, Alaska.

Funding was provided by the Gordon and Betty Moore Foundation, the National Science Foundation, the U.S. Fish and Wildlife Service and the Natural Sciences and Engineering Research Council of Canada.

For more information:
Rogers, lauren.rogers@bio.uio.no
Schindler, 206-616-6724, deschind@uw.edu
Suggested websites:
--Paper abstract
http://www.pnas.org/content/early/2013/01/15/1212858110.abstract
--Proceedings of the National Academy of Sciences
http://www.pnas.org/
--Daniel Schindler
http://fish.washington.edu/people/schindler/

Sandra Hines | Newswise
Further information:
http://www.uw.edu

More articles from Ecology, The Environment and Conservation:

nachricht Coorong Fish Hedge Their Bets for Survival
27.03.2015 | University of Adelaide

nachricht Greener Industry If Environmental Authorities Change Strategy
27.03.2015 | University of Gothenburg

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Experiment Provides the Best Look Yet at 'Warm Dense Matter' at Cores of Giant Planets

In an experiment at the Department of Energy's SLAC National Accelerator Laboratory, scientists precisely measured the temperature and structure of aluminum as...

Im Focus: Energy-autonomous and wireless monitoring protects marine gearboxes

The IPH presents a solution at HANNOVER MESSE 2015 to make ship traffic more reliable while decreasing the maintenance costs at the same time. In cooperation with project partners, the research institute from Hannover, Germany, has developed a sensor system which continuously monitors the condition of the marine gearbox, thus preventing breakdowns. Special feature: the monitoring system works wirelessly and energy-autonomously. The required electrical power is generated where it is needed – directly at the sensor.

As well as cars need to be certified regularly (in Germany by the TÜV – Technical Inspection Association), ships need to be inspected – if the powertrain stops...

Im Focus: 3-D satellite, GPS earthquake maps isolate impacts in real time

Method produced by UI researcher could improve reaction time to deadly, expensive quakes

When an earthquake hits, the faster first responders can get to an impacted area, the more likely infrastructure--and lives--can be saved.

Im Focus: Atlantic Ocean overturning found to slow down already today

The Atlantic overturning is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. Also known as the Gulf Stream system, it is responsible for the mild climate in northwestern Europe. 

Scientists now found evidence for a slowdown of the overturning – multiple lines of observation suggest that in recent decades, the current system has been...

Im Focus: Robot inspects concrete garage floors and bridge roadways for damage

Because they are regularly subjected to heavy vehicle traffic, emissions, moisture and salt, above- and underground parking garages, as well as bridges, frequently experience large areas of corrosion. Most inspection systems to date have only been capable of inspecting smaller surface areas.

From April 13 to April 17 at the Hannover Messe (hall 2, exhibit booth C16), engineers from the Fraunhofer Institute for Nondestructive Testing IZFP will be...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

10. CeBiTec Symposium zum Big Data-Problem

17.03.2015 | Event News

 
Latest News

Two Most Destructive Termite Species Forming Superswarms in South Florida

27.03.2015 | Agricultural and Forestry Science

ORNL-Led Team Demonstrates Desalination with Nanoporous Graphene Membrane

27.03.2015 | Materials Sciences

Coorong Fish Hedge Their Bets for Survival

27.03.2015 | Ecology, The Environment and Conservation

VideoLinks
B2B-VideoLinks
More VideoLinks >>>