Can blue-green infrastructure approaches create functional estuary habitat for salmon in urban waterways?
Long Live the Kings (LLTK) is leading a new partnership with Vigor and the University of Washington (UW)’s Wetland Ecosystem Team to restore habitat along the Harbor Island shoreline within the Duwamish estuary. This project will evaluate the effectiveness of a blue-green infrastructure approach to create functional estuary habitat for juvenile salmon along working shorelines. The partnership between LLTK, Vigor, and UW exemplifies collaboration across sectors to support the economy and environment. Lessons learned from this project can support future restoration projects within urban waterways.
Working waterfronts and waterways are essential components of our economy and are fundamental to our regional identity. The goal of “blue-green infrastructure” is to integrate natural ecological systems into working waterfronts, to serve environmental health alongside industrial and economic needs. The Duwamish estuary is an important waterway for many businesses along Harbor Island and the Duwamish River. The estuary also provides vital habitat for outmigrating juvenile salmon. However, over the past century of urban industrialization, the Duwamish estuary has lost 97% of the habitat it once provided these fish.
LLTK’s Salish Sea Marine Survival Project (SSMSP) showed that healthy estuaries are a critical need for young Chinook salmon. Without functional estuary habitat, small salmon are less likely to survive to adulthood. Wild salmon – including Chinook and steelhead – are listed as threatened under the Endangered Species Act, making salmon recovery a priority throughout Puget Sound. In the Duwamish estuary, collaboration between businesses, scientists, and managers is key to creating effective blue-green infrastructure approaches to restoring habitat and recovering salmon populations.
To mitigate the impacts of a working shoreline, Vigor engaged LLTK and UW’s Wetland Ecosystem Team to evaluate the effectiveness of their restoration project with the goal of creating much-needed functional estuary habitat for juvenile salmon. A team of LLTK and UW scientists has developed a pre-restoration baseline by sampling fish and insects at the restoration site and a nearby reference site at Jack Block Park. To evaluate fish use, scientists record fish counts by species (e.g., Chinook salmon, chum salmon), measure and weigh fish to assess their condition, and investigate what they are eating. Scientists also identify and count insects at each site throughout the outmigration period to understand the food resources available to juvenile salmon. Monthly sampling occurred in 2021, throughout the juvenile salmon outmigration (March-June), when estuary habitat plays an essential role in their survival. Results of the pre-restoration monitoring indicate that feeding patterns for juvenile chum salmon captured at the two sites differed but were similar to other highly developed areas of Elliott Bay. Similar types and numbers of insects were collected at the two sites, and both monitoring sites fell in the middle range for other sites in Elliot Bay. Once Vigor’s team completes their restoration work, scientists will conduct similar post-restoration monitoring (planned for 2024-2025) to measure improvements in habitat function, showing before-after comparisons of shoreline vegetation, insect abundance, and presence and feeding of fish in the newly restored intertidal area relative to the reference site. Restoring habitat provides higher quality food for juvenile salmon, enabling them to grow and survive better. Results for an effective habitat restoration would show increased numbers of juvenile salmon at the site, more insects and benthic invertebrates in their diets, and an increase in insects sampled in the restored vegetation, relative to pre-restored and reference conditions.
Comparing salmon and insect use before and after Vigor’s habitat restoration will provide insight into whether blue-green infrastructure approaches are an effective technique for creating functional estuary habitat along working shorelines. If so, Vigor and LLTK plan to promote the effort and support other businesses and land owners interested in adopting similar restoration projects to support salmon recovery.
Acres of Habitat
Years of Monitoring
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Senior Project Manager (she/her/hers)