A Deep Dive into Herrera’s Snorkeling Survey at Lake Sammamish

Spanning 14 miles through Western Washington, the Sammamish River is home to several native and non-native fish populations. Over the past 150 years, significant human-induced changes, such as navigation and flood control projects, have altered the hydrology of the watershed putting aquatic wildlife at risk. In 1964, the US Army Corps of Engineers completed a flood mitigation project that straightened and deepened the Sammamish River. These alterations led to an increase in river flow, velocity, and erosive forces resulting in a decrease in high-quality salmonid habitat. By eliminating habitat features needed for spawning and migration, the Sammamish River has seen a dramatic decline in the abundance and geographic distribution of both anadromous and resident salmonids.

In response to bank erosion along the Sammamish River Trail, the King County Ecological Services Unit installed pieces of large woody material (LWM) along the right bank to restore habitat while protecting banks from erosion. The County also planted native plant species to restore the right bank.

To evaluate juvenile salmonid use of the engineered log structures (ELS) in the Sammamish River, Herrera’s team of biologists conducted snorkel and habitat surveys throughout the river.  Double pass snorkel surveys took place at four sites in Woodinville and Redmond, each including habitat units with ELS and a control site that does not include placed LWM. Herrera’s biologists conducted fish counts at each habitat unit, surveying each unit twice and identifying fish by species. In addition to fish counts, Herrera measured habitat characteristics, including water depth and flow velocity, at areas representative of the entire habitat unit. The findings of this assessment will be used to inform the design of future restoration projects in the Sammamish River.