Each year wild salmon return to the streams in which they were born to spawn and die. Salmon fishery managers must ensure that adequate numbers of fish return each year to spawn and produce offspring for future harvest. It is expensive and labor intensive to count returning salmon, especially in remote streams.
Researchers at the University of Alaska Southeast, Auke Bay Laboratories, Oregon State University, the UK and China have found that salmon DNA collected in water samples from Auke Creek can be used to infer the number of salmon passing upstream to spawn. Two of the authors on the published paper who contributed to the research are former UAS Biology students now in graduate school, Josh Russell and Donovan Bell. Russell is currently enrolled in the UAF College of Fisheries and Ocean Sciences program, and Bell is in the biology graduate program at the University of Montana.
This form of DNA, termed "environmental DNA" or "eDNA", can be collected from water samples. Water samples are then filtered and probed using molecular genetic techniques to quantify the amount of DNA belonging to each salmon species, providing insights into the number of salmon upstream.
In this study, salmon entering Auke Creek were counted by hand by UAS undergraduates and National Marine Fisheries Service employees. Water samples were then collected from Auke Creek and the eDNA from coho and sockeye salmon in water samples was quantified to see whether it predicted the number of hand-counted salmon.
The researchers report in a paper just published in Molecular Ecology Resources that simple models combining eDNA counts and stream flow accurately detected pulses in coho and sockeye salmon as they migrated upstream to spawn. The upshot for salmon management in Alaska is that eDNA collection from water samples may provide a cheap means to track the abundance of salmon returning to spawn in creeks where other survey methods are logistically challenging or prohibitively expensive. This method of monitoring salmon runs could save the State of Alaska a great deal of money over existing methods. Future efforts will be directed at determining whether these findings hold in locations beyond Auke Creek.
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