Study explores Dungeness crab movement in central Puget Sound
Lurking in the depths of central Puget Sound lies a labyrinth of seafloor pathways that Dungeness crab inhabit.
As they scurry along the sea bottom, it is difficult to track their whereabouts, but a collaborative study between the Washington Department of Fish and Wildlife (WDFW) and the Suquamish Tribe hopes to shed light about crab movement within Puget Sound’s Marine Area 10 (Seattle and Bremerton Area).
During a four-day period in late September, WDFW and the Suquamish Tribe captured, tagged and released 555 legal-size male Dungeness crab. The project spanned across six locations in Marine Area 10 from Alki Point in West Seattle north to Apple Cove Point near Kingston.
During the winter season crabbing opener on Oct. 1, one tagged crab was reported from Elliott Bay. Since then, another four more tagged crab were reported by anglers at Kingston, Shilshole Bay, and the Elliott Bay/Magnolia area.
“This study will help us determine how crabs move around in central Puget Sound,” said Katelyn Bosley, WDFW crustacean program leader. “This could even provide more insight about crab abundance and assist us in how we manage crab fishing seasons and set annual catch quotas.”
Each tagged crab features a thin green, wire-like marking devices measuring two inches long. Each tag has its own individual identification number and a phone contact.
Study researchers inserted each tag into the back side of the crab above the hind legs on the lower side of the carapace and right along the “suture line.” This is an area of the exoskeleton that splits when the crab molts. Lab studies have shown a crab can still retain the tag even after going through the molting process multiple times.
Researchers measured each crab; noted for shell hardness to indicate the stage of molting; and the location of where they were caught and released. There’s no need for anglers to be concerned about consuming a tagged crab.
Crabbers who catch a tagged crab are asked to call the phone number and leave a voicemail or provide a text message. A webpage link will be provided to submit the information, or crabbers may leave a detailed message, which will be added to the WDFW database.
Within the webpage link, crabbers can input the tag identification number; approximate location coordinates “latitude and longitude” (the webpage is GPS enabled and there’s also a map to pin the location) of where the crab was caught; catch date; shell condition (optional); and additional comments.
Dungeness crab are managed in recreational and commercial fisheries under numerous distinct marked boundary lines within Puget Sound. Each marine area has its own specific catch quota, and this study could be an important link to better understand their whereabouts and movements.
WDFW and tribal co-managers conduct test fisheries regularly in Puget Sound to determine Dungeness crab abundance and help set winter and summer fishing seasons.
This isn’t the first time a study on Dungeness crab movement has occurred in the Puget Sound region.
WDFW conducted a crab tagging study along the western side of Hood Canal, around Port Townsend and Discovery Bay in the eastern Strait of Juan de Fuca from 2002 to 2007. During that study period, a total of 7,137 tagged crab were released with 567 retrieved.
“Since that time, we’ve explored repeating that study in other places of Puget Sound where there are pressing management questions,” Bosley said. “We have low or poor crab populations within Marine Areas 10, 11, and 13, and are hopeful studies like this can lead to creating more viable sustainable fisheries in Puget Sound.”
WDFW conducted a pilot run where 100 tagged crab were released in Port Townsend Bay located in Marine Area 9 (Admiralty Inlet). Crabbers are asked to report if they catch a tagged crab in Marine Area 9.
This past April, the Swinomish Tribe conducted a similar crab tagging study in Marine Area 8–1 (Deception Pass, Hope Island, and Skagit Bay) where about 500 tagged crab were released in Similk Bay.
“In the recreational crab fisheries this past summer, several of the blue colored tags were reported by anglers in that area,” Bosley said.
Through Oct. 7, the Swinomish Tribe have recovered 61 tags with 43 reported from the summer recreational crab season and 18 from commercial crabbers.
In May, a tribal test fishery caught another tagged legal-sized male crab in Skagit Bay, south of where it was originally released. To read about the Swinomish Tribe’s tagging study, refer to the Northwest Indian Fisheries Commission webpage.
To get a better understanding of the Dungeness crab population, WDFW also held a collaborative tagging/shell condition workshop in Port Townsend this past June. Attendees included Lummi, Suquamish, Jamestown, Port Gamble, Skokomish, Puyallup, and Swinomish tribal representatives, WDFW coastal shellfish managers, and coordinators from the Pacific Northwest Crab Research Group.
More information about crab management is available on WDFW’s website.
