The war against the invasive European green crab continues in Puget Sound, as this year’s Legislature offers financial support, while the Puget Sound Crab Team responds to crabs being caught for the first time in Samish Bay in North Puget Sound and at Kala Point near Port Townsend.
In other parts of the country where green crabs have become established, the invaders have destroyed native shoreline habitat, diminished native species and cost shellfish growers millions of dollars in damages. See Environmental Protection Agency report (PDF 1.3 mb).
Clik here to view.
Map: Washington Sea Grant
In Puget Sound, it’s hard to know whether the crabs are being trapped and removed rapidly enough to defeat the invasion, but so far humans seem to be holding their own, according to Emily Grason, who manages the Crab Team volunteer trapping effort for Washington Sea Grant.
“The numbers are still in line with what we saw the past two years,” Emily told me. “Since the numbers have not exploded, to me that is quite a victory. In other parts of the world, they have been known to increase exponentially.”
The largely volunteer Crab Team program is focused on placing baited traps at 56 sites in Puget Sound, as shown in the first map on this page. About 220 trained volunteers are involved in that work, with various federal, state and tribal agencies adding about 40 additional people.
Last year, 69 78
crabs were caught in the traps. All but eight of those were on or
near Dungeness Spit, where officials with the U.S. Fish and
Wildlife Service have increased their trapping in an effort to
catch every crab willing to crawl into a trap. The agency manages
the Dungeness National Wildlife Refuge.
In Samish Bay, east of the San Juan Islands in North Puget Sound, three green crabs — including a female bearing eggs — were captured in January while shellfish growers were tending to shellfish beds in the bay. This was the first time that green crabs have been caught in the winter, when they usually move offshore, according to Emily. For that reason, the overall trapping program begins in April and ends in September. But far out on the mudflats, during a low tide, the crabs might be found by those working the shellfish beds. See Emily’s Crab Team blog post from Jan. 23.
Staffers at Padilla Bay National Estuarine Research Reserve added a fifth trapping site in an extremely muddy area of Samish Bay, an area that would be tough for volunteers to monitor, Emily said.
A new Port Gamble site was added in an effort to detect any crabs that may have arrived during their larval stage and begun to grow. Port Gamble on the Kitsap Peninsula is considered to be in the proximity of Kala Point near Port Townsend, where a single green crab was found in September, just before the end of the trapping season. Further extensive trapping located another green crab in nearby Scow Bay between Indian and Marrowstone islands. See Emily’s Crab Team blog post from Sept. 25.
The monitoring at Point Julia in Port Gamble Bay will be managed by the Port Gamble S’Klallam Tribe, which may propose additional sites in the area.
Based on research since the Crab Team was formed in 2015, more crabs are caught in May than any other month, Emily told me, so everyone is waiting to see what shows up this month. As the waters warm and the crabs go out in search of food, they may become more vulnerable to trapping. So far this spring, 16 green crabs have been trapped along Dungeness Spit with one from nearby Sequim Bay.
Another big trapping month comes in August, before the crabs move offshore, she said.
The trapping effort is geared to catching as many crabs as possible at a young age, because a large population of breeding adults in any location could threaten to spread the infestation throughout Puget Sound. Having Crab Team volunteers putting out their traps in strategic locations increases the probability that green crabs will be found before they get established. If needed, larger eradication or control efforts can be launched with the help of other agencies.
As part of the effort, the Washington Department of Fish and Wildlife added a staffer last year to do spot checking in vulnerable areas not regularly trapped. That increases the chances of detecting an invasion.
For the first time this year, the Legislature funded the Crab Team’s operating budget, which allows Emily and other Crab Team leaders to focus on finding crabs, rather than spending their time searching for funding to keep the program going.
The hope, of course, is that fewer crabs will be caught this year, as an indication that the population is being held in check. It would be nice to think that all the major infestations have been found.
“We hope that this is going to be an easier year,” Emily said, “but we don’t get to determine that. We have to be responsive to whatever happens.”
Officials working along the Washington Coast, led by the Makah Tribe, have their hands full with an invasion that may have started as early as 2014 and has resulted in more than 1,000 green crabs being caught. Check out the story on the website of the Northwest Indian Fisheries Commission.
The interactive map below allows for selection of trapping sites, locations where crabs have been found and areas with suitable habitat for invaders. For those who would like to get involved in the Crab Team’s efforts, check out Sea Grant’s website and the “Get Involved” page.
This blog post was revised from an earlier version to correct changes in the total number of green crabs found last year and to clarify the overall effort.
