Nearly 100 invasive European green crabs were trapped along Dungeness Spit near Sequim this past spring and summer — far more than anywhere else in Puget Sound since the dangerous invaders first showed up last year.
Photo: Allen Pleus, WDFW
Despite the large number of crabs found in this one location, green crab experts remain undeterred in their effort to trap as many of the crabs as they can. And they still believe it is possible to keep the invasion under control.
“In a lot of ways, this program is functioning much as we had hoped,” said Emily Grason of Washington Sea Grant, who is coordinating volunteers who placed hundreds of traps in more than 50 locations throughout Puget Sound. “We look in places where we think the crabs are most detectable and try to keep the populations from getting too large, so that they are still possible to control.”
After the first green crabs were found on Dungeness Spit in April, the numbers appeared to be tapering off by June, as I described using a graph in Water Ways on June 24. The numbers stayed relatively low, with three caught in July, two in August, three in September and two in October. But they never stopped coming.
The total so far at Dungeness Spit is 96 crabs, and more can be expected when trapping resumes next spring. The good news is that all the crabs caught so far appear to be just one or two years old — suggesting that they likely arrived as free-floating larvae. That doesn’t mean the crabs aren’t mating at Dungeness Spit, but the trapping effort has reduced the population to the point that males and females are probably having a tough time finding each other.
Officials with the U.S. Fish and Wildlife Service, which has taken charge of trapping at Dungeness Spit, will need to decide whether to attempt a complete eradication of the local green crab population, according to Allen Pleus, coordinator of Washington State’s Aquatic Invasive Species Program. That would involve managing a large number of traps until no more crabs are seen. The alternative, he said, would be to manage the crab population with fewer traps and make further decisions down the line.
During one three-day stretch last year, 126 traps were deployed in areas on and near Dungeness Spit, part of the Dungeness National Wildlife Refuge managed by the Fish and Wildlife Service.
Even with the most exhaustive trapping program, there is no guarantee that green crabs won’t be found again, Allen said. The likely source of the crab larvae is an established population of green crabs in Sooke Inlet on Vancouver Island, just across the Strait of Juan de Fuca from Dungeness Spit.
Allen said he is disappointed that crabs continued to be caught on or near Dungeness Spit — mainly in one small area near the connected Graveyard Spit. “But I am very impressed with the dedication of the U.S. Fish and Wildlife Service, which continued to trap throughout the summer,” he said.
While there is no evidence so far that the invading crabs have reproduced at Dungeness Spit, it is possible that mating took place. If so, everyone involved in the green crab effort could face a whole new group of young crabs next year.
I have to admit that I was worried last spring that funding for the essential volunteer effort would run out as officials scrambled to finance the start of trapping season. But the Environmental Protection Agency agreed to fund the project through next year under the Marine and Nearshore Grant Program.
Meanwhile, Allen said he is working with Canadian officials to see what can be done about reducing the population of green crabs in Sooke Inlet, which is likely to remain a source of the invasive crabs coming into Washington state. The Canadians have their own concerns about green crabs, which can severely damage commercial shellfish operations and disrupt critical eelgrass habitats.
“Sooke Inlet is the only known population established in the Salish Sea,” Allen said. “We are working with Canada and setting up meetings this winter to continue our discussions.”
Canadian officials are monitoring for green crabs on their side of the border, but the effort is much less than in Puget Sound. It appears that only limited efforts have been made so far to control the Sooke Inlet population and reduce the amount of invasive crab larvae heading to other areas in the Salish Sea.
Researchers are still investigating the conditions that allow green crab larvae to survive long enough to grow into adult crabs. It appears that larvae move up the coast from California during warm years and particularly during El Niño periods, Emily told me. That may explain why the Puget Sound traps began catching so many crabs the past two summers.
“The signal we are seeing does point to 2015 and ‘16 as being the first arrivals,” she said. “Our working hypothesis is that warm years are spreading larvae.”
That could offer renewed hope for the immediate future, since El Niño is over and we may be going into cooler La Niña conditions next year.
No new crabs have shown up in the San Juan Islands, where Puget Sound’s first green crab was discovered last year. But two more were found about 30 miles away in Padilla Bay, where four crabs were caught last fall.
New areas with green crabs this year are Lagoon Point on Whidbey Island, where two crabs were caught, and Sequim Bay, not far from Dungeness Spit, where one crab was caught.
The latest concern over green crabs is Makah Bay on the outer coast of Washington near the northwest tip of the Olympic Peninsula. In August, a beach walker spotted a single green crab on the Makah Tribe’s reservation and sent a picture to the Puget Sound Crab Team, which confirmed the finding. Tribal officials launched a three-day trapping effort last month and caught 34 crabs — 22 males and 12 females — in 79 traps.
An aggressive trapping effort is being planned by tribal officials for the coming spring. Interested volunteers should contact Adrianne Akmajian, marine ecologist for the Makah Tribe, at marine.ecologist@makah.com
The Makah effort is separate from the Puget Sound Crab Team, which encourages beach goers to learn to identify green crabs by looking at photos on its website. Anyone who believes he or she has found a green crab should leave it in place but send photographs to the crab team at crabteam@uw.edu
Emily said she is most proud of all the people and organizations that have come together as partners to quickly locate the invasive crabs and advance the science around the issue. Such cooperation, she said, makes the impact of the program much greater than it would be otherwise.
Supposedly they are good to eat. Make it open season year round so people will want to go get them. Humans seem to have a way with making a species extinct; let’s do that here!
Green Crab have been in Willapa Bay since 1965. See Between Pacific Tides , Calvin, Ricketts and Dr. Joel Hedgepeth of OSU who observed them there on many occasions. They have been here more than 65 years.
They were introduced to Elkhorn Slough by Ed Ricketts for Pacific Biological Supply and Carolina Biological Supply as dissection specimins for HS biology classes. I dissected one at Woodbury HS in Advanced Biology in 1960.
They were also frequently sent to and dumped on the West Coast along with East Coast Marine Algae species with “Authentic Maine Clambakes”(including live East Coast Lobsters(Homarus americanus) for “color and authenticity”
Arriving overnight by FeDeX and UPS from Portland ME. Through out the 1970’s and 1980’s. I last saw a shippment to Willapa Bay on a FeDeX delivery truck in May if 1986 when it picked up a out going delivery from my clam and oyster farm in Shelton WA, Little Skookum Shellfish Growers.
This all is in the open literature. Sorry.
Peter, Thanks for writing. It appears you have some important information on this topic.
Numerous reports and summaries I have seen describe the European green crab as first being discovered in June of 1998 in Willapa Bay, followed by Grays Harbor a month later. That’s not to say that they didn’t arrive earlier and possibly died out. If green crabs were seen living on the Washington coast earlier than 1998, I think you should share that documentation with researchers studying the invasion as well as officials with the Washington Invasive Species Council. I would also be interested in seeing it.
If true, an important question would be whether those earlier crabs were breeding. Since 1998, researchers believe the population has expanded and then contracted.
Until last year, an extensive trapping program in many areas of Puget Sound failed to locate any green crabs, according to those involved in the program. The one crab found on San Juan Island is reported as the first ever discovered in the inland waters of Washington state. So far, no breeding has been confirmed.