Little European green crabs create big concern for shellfish industry
May 23, 2025, 5:03 AM
A Washington State Department of Fish and Wildlife staffer holds two European green crabs. (Photo courtesy of WDFW)
(Photo courtesy of WDFW)
Some little crabs with big appetites are getting the attention of Washington’s shellfish industry.
Washington has the most productive shellfish farms in the nation. It’s a more than $200 million industry, annually.
So when European green crabs invaded Washington waters in the 90s—feasting on clams, oysters, muscles, and more—shellfish producers started trapping them. They’ve been successful, catching more than 1.2 million of them in Willapa Bay and Grays Harbor last year alone.
WSU Extension specialist on European green crabs
It’s a big headway, but there’s a small problem: Little European green crabs and the amount those juvenile crabs can eat.
“It’s a big appetite,” said Laura Kraft, a Washington State University Extension specialist who just wrapped up a study on the juvenile crabs. “And what we found is that when we fed them juvenile Pacific oysters, the little crabs were eating almost the same proportion as the big crabs, which really shocked us.”
In addition, European green crabs, of all ages, threaten native eel grass, which provides habitat for salmon and other fish. Therefore, Kraft said this is prompting a shift in how the shellfish industry and advocates fight the invasive species, by trapping both older and younger crabs.
“They do require a different type of trap,” she said. “Essentially, we change the size of the entry hole into the trap.”
They’re also looking beyond trapping as they work to manage—if not eradicate —European green crabs.
“WSU this summer is looking forward to looking at an attractive sex pheromone to remove male crabs from the bay,” Kraft shared.
It could be used to lure unwitting crabs into traps or to disrupt the mating cycle altogether.
“Essentially putting out so much male pheromone that the males can’t even find the females,” Kraft explained.
She said a similar process is used to manage codling moths, without pesticides, to protect apple crops.
Read more of Heather Bosch’s stories here.
Follow @http://www.twitter.com/heatherbosch
