The invasive European green crab count continues to rise on the Dungeness Spit.
As of Friday, May 12, researchers said 52 crabs have been caught by crews who quadrupled the amount of traps placed in Dungeness’ waters.
Lorenz Sollmann, deputy project leader at the Washington Maritime National Wildlife Refuge, said staff and volunteers put out 108 traps multiple times last week and will do so again this week.
“We’ve got out what we can handle,” he said.
Sollmann said crews have a good system down of cutting bait, checking traps and recording where green crabs are found.
Crews at the Dungeness Wildlife Refuge first found a few green crabs on April 13, which is the first sighting of the crustacean along the North Olympic Peninsula.
The green crab, considered one of the worst invasive species on the planet by scientists, is identifiable by its five spines on each side of its eyes, and despite its name, it can be green, brown or reddish typically with orange joints, said staff with Washington Sea Grant’s Crab Team.
Researchers said the crab often is blamed for damaging shellfish harvests and sea grass beds in the Northeastern U.S.
Dr. Sean McDonald with the Crab Team said there is a movement for homogenizing species around the globe but the effort doesn’t work out.
“Green crabs are never going to compete with local crabs like the Dungeness crab (economically),” he said. “If you care about native ecosystems, like the Dungeness crab and eelgrass, resist the spread of green crab.”
Dr. Emily Grason, Crab Team project coordinator, said the green crabs will out-compete Dungeness crab when they are the same size but if the native crabs are larger then they will out-compete the green crab.
Plan of action
More than 15 stakeholders from biologists to state officials met in person and via phone at the Jamestown S’Klallam Tribe’s main campus on May 4 to discuss options to prevent the green crab from growing its population.
“We’re trying to get rid of them as soon as possible,” said Allen Pleus, Aquatic Invasive Species coordinator for the Washington Department of Fish and Wildlife.
Traps have been placed across the Dungeness Spit, researchers said, but all of the crabs were found in the same channel on Graveyard Spit, across from Dungeness Landing near Sequim.
Staff with the Wildlife Refuge say the habitat there is terrific for green crab but it’s hard for crews to access because it’s so mucky.
Neil Harrington, environmental biologist for the Jamestown S’Klallam Tribe, said their staff have done some limited trapping in south Sequim Bay but haven’t caught any green crabs.
He said they are working with other stakeholders to place traps in possible green crab habitat in Sequim and Dungeness bays a few times this season.
Pleus said training stakeholders like the Jamestown S’Klallam Tribe through Washington Sea Grant to seek out green crabs is one of the next steps they hope will happen with small teams working in designated areas with 20-30 traps under an aquatics invasive species trapping permit.
“We’re going to find more crab,” Pleus said. “With resources being what they are, we can’t have someone out there everyday, all summer long.”
Despite Graveyard Spit being a good spot for the green crab, Grason said researchers don’t believe there is much good habitat along the strait west of Dungeness.
However, Sea Grant employees identified a few sites they hope to work with property owners to explore monitoring options for green crab including Hoko River, Clallam River, Pysht River and Port Angeles Lagoon.
The Crab Team monitors 41-plus sites with 170-plus volunteers.
When a green crab was discovered on Sept. 19, 2016, in Padilla Bay, the Crab Team led three days of intensive trapping efforts placing 368 traps at 31 sites.
In early May, one crab was spotted at an early detection site in Padilla Bay near Mount Vernon again leading Padilla Bay National Estuarine Research Reserve staff to place more traps as a precaution, Grason said.
The European green crab was first reported on the U.S.’s East Coast in 1817 and in San Francisco in 1989, Grason said. It was first observed in Washington in 1998 and by 2012 it was unintentionally brought by human transport to the Sooke Inlet, west of Victoria, B.C., she said.
Dungeness’ population is the largest reported so far in inland Washington but where it’s coming from is something researchers are still trying to pinpoint.
McDonald said he and other researchers don’t see human transport or spawning and traveling from northern British Columbia because of the temperatures and currents as possible causes.
Traveling from Vancouver Island, Oregon, other parts of Washington or Sooke Basin all remain possibilities because of their distance and/or temperatures of those areas, McDonald said.
Green crab larvae in its earliest stages can travel upwards of 100 kilometers, he said.
One female can release up to half-a-million larvae per brood, Grason said, and research states it’s possible females can have more than one brood a year.
But if local green crabs are mating or not is unknown, researchers report.
Of the 52 caught on Graveyard Spit, 33 are males and 19 are females, Sollmann said.
The largest crab was a 62 millimeters-wide female (2.4 inches), which can be reproductive at 45 millimeters (1.8 inches), Grason said.
Four moltings have been found so far, which signifies those crabs could be ready to mate but Grason said crabs molting or hardening their new shells do not come to traps as often nor will crabs in pre-mating embrace.
For more resources on identifying the green crab, places to look and/or volunteering, visit http://wsg.washington.edu/crabteam. For those who may have found a green crab, send photographs and location to the Crab Team at firstname.lastname@example.org.