Bugs and Dirt Help Tell the Story of the Elwha River Restoration

The Lower Elwha Klallam Tribe has been sampling sediment and insects near the mouth of the Elwha River for a decade, tracking how the estuary has been changed by the removal of two fish-blocking dams in 2012 and 2014.

Dam removal released sediment down the river that created approximately 80 acres of beach at the mouth and helped form the current estuary. The tribe has seen a significant change in the fish and insects using the estuary over the past decade.

“We want to correlate between findings of the fish diet and sediment samples, so we can determine what the salmon are selecting to eat,” said Rebecca Paradis, a tribal project biologist. “Doing this work over the past decade has helped us see what bugs are in the sediment and if there has been a species shift or change in structure and population as the estuary has changed.”

The sediment was sampled specifically for invertebrates in 2007, 2013 and 2017 so biologists could assess habitat conditions before, during, and after dam removal. The collected insects were examined by an entomologist, and the results have been compared to the stomach contents to see what fish may or may not have eaten.

“The 2013 data appeared to suggest that the ongoing release of waves of fine sediment combined with low water clarity resulted in fewer bugs in the sediment, and that was also reflected in the stomachs of juvenile salmon,” said Matt Beirne, the tribe’s natural resources director.

Lower Elwha Klallam Tribe natural resources technician Justin Stapleton picks through a sediment sample taken from the estuary at the mouth of the Elwha River. Photo: T. Royal