Spawning Salmon Are Changing the Natural Environment

A study from Washington State University finds that the act of mating by salmon is having an impact on stream beds and watersheds, creating changes to the natural environment. As described in Lab, the report "Sex that moves mountains: The influence of spawning fish on river profiles over geologic timescales"by researchers Alexander K. Fremier, Brian J. Yanites, and Elowyn M. Yager describes how the fish can alter the landscape after generations (counted in millions of years) of spawning.

Alex Fremier, lead author of the study and associate professor in the WSU School of the Environment, said female salmon "fluff" soil and gravel on a river bottom as they prepare their nests, or redds. The stream gravel is then more easily removed by flooding, which opens the underlying bedrock to erosion.

"The salmon aren't just moving sediment," said Fremier. "They're changing the character of the stream bed, so when there are floods, the soil and gravel is more mobile."