Tuesday, February 11, 2020

Use of Field Notebooks from more than a Century Ago Provide Data on Salmon Population Change

Environmental & Science Education
History of Science
Nature of Science
Climate Change
Edward Hessler

From 1919 to 1948, government employees collected information about sockeye salmon runs in the Skeena River (British Columbia). They recorded weight, length, sex, and catch date for a sample during each day of the runs. In addition, a scale was scraped from the salmon and pasted, using the slimy glue of the salmon's skin, next to the record. The scales include a yearly growth ring, just like a tree and these can be counted.

The original notebooks were boxed, stored and forgotten. Twenty-three years ago, a fisheries biologist who was studying sockeye salmon in the Gulf of Alaska found them. He was in search of more detailed data than the averages from the Skeena logs. It was a question he was always asking other fisheries biologists. While "attending an unrelated meeting...he learned the records were sitting in a closet down the hall."

I can only imagine his surprise and pleasure when he opened the notebooks to find fish scales which he knew "had potentially preserved salmon DNA, which could enable modern molecular biologists to link the long-dead fish to current wild Skeena populations, each genetically distinct because adults breed in a complex of nursery lakes where their offspring grow for at least a year before migrating downstream to the sea." 

This has resulted in a paper in which researchers have...sequenced DNA from the scales of 3400 fish caught between 1913 and 1923) in Conservation Letters and a short article about the research in Science (August 20, 2019) by staff writer Lesley Evans Ogden. Ogden's essay includes two photographs, one of an open notebook held over a bin of  stored notebooks and of a technician counting the age rings of a fish scale.

The Skeena River is home to 13 major sockeye salmon populations and the research team  found that "declines have been more precipitous and widespread than previously understood." The river's sockeye salmon populations have plummeted "by 56% to 99%" over the period studied. Not one population has not been affected.

Now you might expect that the cause is due to habitat destruction, e.g., logging and agriculture. Nope. Overfishing. Climate change "may also be influencing salmon success." There are data to support this. The northern populations "in Alaska are thriving despite heavy fishing pressure."

Please take a look at Ogden's story for more details and quotes by fishery professionals.

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