In the coming week resource managers on the Dungeness Spit look to wrap up their season’s hunt for the invasive European green crab.
The crabs were discovered last April on Graveyard Spit north of Dungeness Landing, and now total 93 green crabs — 54 males and 39 females — as of Sept. 21.
Lorenz Sollmann, deputy project leader at the Washington Maritime National Wildlife Refuge, said because of high tides this week, staff and volunteers will set traps Oct. 2-6 before determining whether or not they’ll stop for the season and pick up again in April 2018.
Dr. Emily Grason, Crab Team project coordinator through Washington Sea Grant, said research in Willapa Bay by Long Beach in the late 1990s and early 2000s showed green crab don’t come to traps in the same numbers in the winters as the summer.
“It doesn’t make a good use of people’s time (to search in winter months),” she said.
Over the summer, Sollmann has worked with fellow staffers and about 20 volunteers, including some with Clallam County Streamkeepers, to place as many as 127 traps at a time.
Species with clout
The European green crab, known for its five spines on each side of its eyes, is considered one of the most invasive species on Earth, according to scientists, and it has been reported to have damaged shellfish harvests and seagrass beds predominately in the Northeastern United States.
The San Francisco Chronicle reported in the Aug. 17 story, “Invasive crabs flourish in Marin lagoon, despite eradication efforts,” that the man-made lagoon northwest of San Francisco holds an infestation of more than 100,000 green crabs that locals have been unable to contain despite trapping efforts since being discovered in San Francisco Bay in 1989.
Grason said research shows a female green crab can release up to 500,000 larvae at a time, and that it’s possible they have more than one brood a year.
Sollmann said if local green crabs had bred by now in Dungeness, larvae would have showed up in their minnow traps.
Resource managers also estimate the green crabs in Dungeness all come from the same 2016 age group because of their similar size.
Things were looking positive for the trapping effort as resource managers went about one month without catching any green crab but two females were captured in the same trap, on separate days two weeks ago, Sollmann said.
“We’ll trap in the next two weeks and see where we’re at,” he said. “We’ve been putting 50 traps out for a few months now.”
Allen Pleus, Aquatic Invasive Species coordinator for the Washington Department of Fish and Wildlife, said resource managers have been trying to “find the needles in the haystack when the populations are small” since April.
“We need to attack it as early as we can,” Pleus said.
“It’s similar to a wildfire and trying to find hot spots. It’s also similar to illnesses like Ebola or avian flu. If you find small pockets, you try to get rid of it before it gets exponentially worse.”
Sollmann said rapid response to trapping is the “most efficient and economically feasible way of handling the crabs.
“If we can control the population in this estuary, then we’re preventing it from infesting another one down the water. It’s not like a weed you can spray and it’ll go away.”
Early detection monitoring has been ongoing since 2001 along the Dungeness Spit and the first green crabs were discovered in April after Crab Team staff members helped realign traps to possible habitat spots.
Sollmann said Dungeness Spit is a collection point for things like marine debris and logs and he made an effort to continue twice-a-month trapping after grant funding ran out in 2010.
“I was afraid we’d miss something,” he said.
Until recently, Dungeness was one of three recent sightings of green crab, including Westcott Bay on San Juan Island and Padilla Bay near Anacortes in the summer of 2016.
However, two more lone green crabs were found on the west side of Whidbey Island at Lagoon Point, a male, in early September, and a female in Sequim Bay on Aug. 15.
Grason said the Whidbey Island crab is the furthest a green crab has been caught in Puget Sound.
She theorizes that it’s possible the Whidbey Island crab is linked to Dungeness’ crab, but its size indicates it was born in 2017 compared to the local crab born sometime in 2016.
Volunteers plan to do another trapping on the island to assess next steps, Grason said.
In Blyn, Neil Harrington, environmental biologist for the Jamestown S’Klallam Tribe, led trapping efforts that found the single green crab, likely born in 2016, in the Jimmycomelately Creek estuary in the southern part of Sequim Bay.
In the month since capturing the crab, Harrington said he and coworkers have placed 316 traps over the span across the bay but did not find any more crabs.
He plans to trap a few more locations that he hasn’t covered in the bay in the coming week, but says it may be his last trapping days until next spring, too.
Grason said because of the amount of traps placed and with no other signs of green crabs, Sequim Bay’s crab is “likely one lucky crab who survived a very low probability scenario.”
This winter, Pleus said resource managers will work on developing a management plan for 2018 while expanding partnerships between agencies.
Sollmann estimates his team will start with placing 50 traps next April to assess the number of green crabs and move to monitoring monthly if they aren’t seeing much results from trapping.
“Have we managed to capture every crab? Certainly not, but the numbers are lower,” Grason said about the efforts in Dungeness.
“From our perspective, it’s been really successful and it shows it takes a lot of effort. Their response is ideal.”
Grason plans to work with Sollmann’s staff to analyze their trapping data this season to develop strategies for better trapping in 2018.
As to how the crabs ended up in Dungeness or where they came from is still a mystery.
Grason said they have 15 samples of green crab from Dungeness frozen for a scientist to genetically test, but they continue to seek grant funding in order to pay for the process.
She previously said there are multiple options as to how they arrived here such as floating as larvae from another infested area such as British Columbia’s Sooke Basin, or as far away as Oregon or California.
Crab Team hosts 52 early detection sites with help from more than 200 volunteers and dozens of partner agencies’ staff including working with the Lower Elwha Tribe at the Pysht Estuary southeast of Clallam Bay.
If you’re out and about and you see a green crab, it’s recommended you do the following:
• Identify if it is a green crab such as counting the five spines on each side of its eyes.
• Leave the crab in place because it’s illegal to possess one without a special permit.
• Take several pictures from different angles and distances for identification with a common object next to it for scale.
• Email photos to email@example.com and wait for a response.
For more resources on the green crab, visit https://wsg.washington.edu/crabteam/about/blog/.