No new green crabs have been found, but the search will go on

No European green crabs were caught this week during an intensive two-day trapping program designed to see if any of the invasive crabs have gained a foothold in the San Juan Islands.

These are the locations and number of traps placed on Monday in the northern San Juan Islands. Map: Washington Sea Grant
These are the locations and number of traps placed in the northern San Juan Islands on Monday. // Map: Washington Sea Grant

If you recall, a single adult green crab was trapped Aug. 31 by a team of volunteers in the San Juan Islands. It was the first green crab ever found in Puget Sound, but experts have been worried about the crab for years. (See Water Ways, Sept. 3.) The volunteers are involved in a citizen science monitoring program to locate green crabs when they first arrive in Puget Sound and before they become a breeding population.

The response by professional leaders of the Crab Team was to place 97 traps in and around the location where the first crab was found. The effort was started on Monday and repeated on Tuesday. The maps on this page show the locations and the number of traps place at site on the two days. Hundreds of native crabs were trapped and inspected, but no green crabs were found.

These are the locations and number of traps placed in the northern San Juan Islands on Tuesday. Map: Washington Sea Grant
These are the locations and number of traps placed in the northern San Juan Islands on Tuesday. // Map: Washington Sea Grant

Although no live crabs were found, one molt (cast-off shell) from a green crab was found by Jeff Adams, a marine ecologist for Washington Sea Grant who manages the Crab Team of volunteers. The molt was close to where the live crab was found. The experts have not determined if the molt came from the first crab or if there might be other crabs in the area.

The next step is still being planned. It could involve another intensive trapping effort, perhaps in the spring, as well as increasing the number of volunteer trapping sites in the San Juan Islands. The volunteer program takes a hiatus in the winter, when the crabs are less active, but it will resume in the spring.

The next green crab training program is scheduled for March, when new and former citizen science volunteers will be taught how to identify green crabs and conduct an effective trapping effort in up to 30 locations throughout Puget Sound. To learn more about the volunteer program, check the Washington Sea Grant webpage “Get Involved” or sign up for a free email newsletter called “Crab Team News” (click “Newsletters”).

Emily Grason, Crab Team coordinator for Washington Sea Grant, was involved in the two-day intensive trapping program. Emily blogs about the effort on the Crab Team website:

You may want to review my recent writing project on invasive species for the Encyclopedia of Puget Sound, including a story about green crabs and the volunteer monitoring program.

Sean McDonald of Washington Sea Grant heads out to check on crab traps on Henry Island, not far from where the first green crab was found in Puget Sound. Photo: Emily Grason, WSG
Sean McDonald of Washington Sea Grant heads out to check on crab traps on Henry Island, not far from where the first green crab was found in Puget Sound. // Photo: Emily Grason, WSG

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