Washington Sea Grant researchers analyzed how changes in temperature and salinity affect Dungeness crab, Washington’s most valuable catch, and the less-desirable graceful crab. An experiment was conducted that measured the responses of Dungeness crab and graceful crab to six different temperatures. Similar feeding trials conducted at a common temperature with crabs of various sizes revealed size-specific consumption rates. Bioenergetic models based on the data is used to consider how future conditions may affect crab ecology and to evaluate the robustness of current management strategies.
The West Coast Dungeness crab fishery is worth over $200 million a year. Fishery regulations stipulate that only larger males are to be taken, and only in certain areas during discrete time periods, so as to give the animals an opportunity to reproduce. However, this management strategy may become inadequate if climate change impacts local Dungeness crab reproduction and growth—or the reproduction and growth of a competitor, which shares an ecological niche—the graceful crab. More information is needed to understand how climate change will affect these crab populations and how resource managers should respond.
Preliminary results suggest that graceful crab maintain higher levels of consumption over a broader range of temperatures than Dungeness crab, which could give graceful crab a competitive advantage as water temperatures warm. These results were shared with state and tribal co-managers at the Annual Shellfish Conference in Blaine, Washington, in September 2018. This led to a workshop to evaluate the future research needs for sustainable management of the Dungeness fishery and the formation of the Pacific Northwest Crab Research Group.