Program on the Environment

The introduction of European green crabs (Carcinus maenas) into Washington’s coastal ecosystems poses significant ecological challenges. These invasive crabs impact native biodiversity by competing for resources and altering habitats, which in turn affects many native species. This study explores the impact of European green crab presence on the size and abundance of native fish in Willapa Bay. During my time with the Washington Sea Grant Crab Team, I analyzed image data from their volunteer-based monitoring program, and measured the sizes of Staghorn Sculpin, Prickly Sculpin, and Three-Spined Sticklebacks. Using linear mixed models and graphical analysis, I examined how variations in green crab population density correlate with changes in the size and abundance of fish species at various sites within the bay. Preliminary findings suggest that green crab presence correlates with increased sizes in sculpin species, decreased sizes of Three-Spined Sticklebacks, and no significant findings regarding changes in abundance. However, the observed fluctuations (or lack thereof) are likely influenced by the geographical features of Willapa Bay, the life stages of the fish that inhabit these sites, and other ecological variables. This study highlights the complex interactions between invasive green crabs and native fish populations, advocating for extended research across a broader geographic area. A comprehensive understanding of the ecological impacts requires an examination of the environmental conditions at each site. Such analyses are crucial for developing effective strategies to mitigate the influence of green crabs on local fish species, thereby supporting the conservation of these vital ecosystems.