Scaling shoreline restoration to improve nearshore marine habitat for salmon and forage fishes

Shoreline restoration is a widespread activity with a multitude of ambitions. Goals often include protection of people and property from storms and sea level rise, improvement of habitat for fisheries and protected species, and mitigation of the effects of climate change through investments in blue carbon. However, few studies have directly assessed the impacts of restoration actions on specific ecological or economic endpoints, nor characterized the significance of the surrounding landscape to restoration outcomes. We conducted monthly surveys from April through September in 2018-2021 at six restoration sites in Puget Sound to evaluate associations between shoreline restoration and offshore subtidal fish distribution. We measured the abundance of juvenile salmonids (Chinook and chum), and forage fishes (Pacific herring and surf smelt), at restoration sites as compared to nearby armored and reference shorelines. At a local spatial scale, we found limited support for associations between shoreline restoration and these subtidal fishes in the 3-10 years since armor removal. However, the presence of eelgrass was heavily influential. We also investigated these relationships with a focus on landscape, rather than local, environmental features such as water quality, shoreline structure, and watershed features. Our results suggest that juvenile forage fish and salmonids are likely responding to broader landscape patterns as well as species-specific habitat needs, information which can be used for prioritizing investments in restoration.