During last fall's salmon run, a University of Washington team collected Coho salmon environmental DNA (eDNA) from the air beside Issaquah Creek, near the Issaquah Salmon Hatchery in Washington. The idea began when researcher Aden Yincheong Ip wondered, after seeing fish jump and water spray while hiking, whether genetic material could be recovered from the air. To test this, the team placed air filters at sites beside the stream and captured Coho DNA at distances of 10 to 12 feet from the river.
Sampling took place on six days between August and October. Filters were left for 24 hours and four filter types were used each time: three vertical filters and an open 2-liter tub of deionized water to collect settling particles. In the laboratory the researchers washed eDNA from the filters and measured it with a Coho salmon–specific tag using polymerase chain reaction. Although salmon DNA in the air was about 25,000 times less concentrated than in the water, airborne eDNA still tracked the hatchery's visual counts over the migration period.
The study, published in Scientific Reports, combined air and water eDNA with the hatchery’s visual counts in a statistical model to follow how salmon numbers rose and fell. The results suggest airborne eDNA can indicate where salmon are and their relative abundance across streams, but variables such as rain, wind, humidity and temperature remain to be explored. Ryan Kelly described the work as at the edge of what is possible with eDNA. The research was funded by the David and Lucile Packard Foundation and Oceankind. Source: University of Washington.
Difficult words
- environmental DNA — DNA left by organisms in the environmenteDNA
- polymerase chain reaction — lab method that copies specific DNA segments
- abundance — amount of organisms in a specific area
- hatchery — place where fish eggs are hatchedIssaquah Salmon Hatchery, hatchery's
- visual count — number observed by people looking at fishvisual counts
- filter — device that removes particles from air or waterair filters, filters
- track — follow a change or location over timetracked
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What are the main advantages and possible limits of using airborne eDNA instead of only water samples for monitoring salmon?
- How might rain, wind, humidity or temperature change the ability to detect airborne eDNA in a stream area?
- If airborne eDNA can indicate relative abundance across streams, how could fish monitoring or conservation work change as a result?
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