Artificial beaver dams saw juvenile coho salmon survival rates go from 8% to 60%

It’s well known that beaver dams transform landscapes. In their absence, artificial versions were built in northern California to recreate lost wetlands – boosting the survival of threatened coho salmon.

The findings are published in Frontiers in Ecology and Evolution . Fish biologist Michael Pollock of NOAA’s Northwest Fisheries Science Center called the results “mind blowing”.

The Scott River valley in northern California was once home to so many beavers it was known as Beaver Valley. Their dams created an enormous riverine wetland, providing habitat for juvenile coho salmon and a host of other wildlife.

Then European fur trappers arrived in the 1830s. Thousands of beavers were trapped and killed, and much of the habitat created by their dams and wetlands was lost – taking with it the cold, slow-moving habitat favoured by coho salmon.