Exploring how Dungeness crab use Olympia oyster habitats with implications for restoration

The goal of this project is to investigate merging the management and restoration of two valuable species in Washington, Dungeness crabs and Olympia oysters. This project aims to meet five objectives: 1) conduct geographically broad observational surveys evaluating species overlap in restored Olympia oysters; 2) evaluate physical aspects of established Olympia oyster restoration that could be leveraged to increase Dungeness crab abundance; 3) correlate physical aspects of oyster restoration that may be used to limit the co-occurence of nuisance species; 4) evaluate differential juvenile Dungeness crab survival from predation in restored Olympia oyster habitats; 5) build a collaborative network of restoration practitioners and scientists to begin to implement multispecies conservation and restoration priorities. This research will allow for more informed, mutually beneficial approaches for the restoration and management of two important species in Washington.

Project background

Despite an increased interest in restoration work, the practice is often limited to specific target species, with success determined by the growth or survival of that species. This siloed approach to single species restoration can create conflicting management plans and priorities. This project instead identifies two priority species for conservation and restoration in Washington, Dungeness crabs and Olympia oysters, to explore for co-occurrence and potential for dual management. Ongoing Olympia oyster restoration sites may provide habitat for juvenile Dungeness crabs; however, they may also facilitate the growth of more harmful species such as the European green crab. This project will explore where and how Dungeness crabs use restored Olympia oyster habitat, as well as what other species may compete with or hinder Olympia oysters or Dungeness crabs, to shed light on these questions.

Results and findings

This project will use two methods of investigation conducted around Puget Sound and  Hood Canal: large-scale observational field surveys and predation assays. The field surveys will measure the abundance of the Dungeness crabs, green crabs, oyster drills, and shore crabs in restored oysters and various paired non-restored habitats. Surveys will also measure the impacts of variation in shell enhancement, including shell elevation placement and shell layer depth, on the abundance of these species Additionally, before-after-control-impact surveys using Puget Sound Restoration Fund’s ongoing restoration plans will further measure how oyster restoration impacts the occurrence of Dungeness crabs and nuisance species. Predation assays will consist of tethering juvenile Dungeness crabs and measuring survival of the crabs after one day. This project aims to align and meet management goals that benefit multiple species.

Contact information

Jodie Toft
Executive Director
Puget Sound Restoration Fund
jodie@restorationfund.org