Large Numbers Of Invasive Crabs Found At Makah Bay, But Lessons Learned Too

Twice as many invasive European green crabs have now been trapped at Makah Bay as first reported earlier this summer, an alarming development but one that’s also providing key insights for the fight to keep the species from spreading into Puget Sound.

SEVERAL DIFFERENT YEAR-CLASSES OF INVASIVE EUROPEAN GREEN CRAB HAVE BEEN FOUND AT MAKAH BAY. (KELLY MARTIN, WASHINGTON SEA GRANT)

Officials from Washington Sea Grant spent three days with tribal managers at the northwestern tip of the Olympic Peninsula and called it “an excellent learning experience.”

“Many parts of the Wa’atch and Tsoo-Yess (River) estuaries superficially appear as if they would be primarily freshwater – not saline enough to allow for the survival of organisms such as shore crabs, staghorn sculpins, and green crab. However, in the summer months when there is little rain and therefore little freshwater input in the rivers, these estuaries remain fairly salty due to tidal fluctuations. This gives us a better idea of what kind of sites green crab are able to inhabit which could be useful as we continue to monitor the Salish Sea,” WSG reported in a blog earlier this month.

They’ve already identified dozens upon dozens of sites with high or medium suitability for the crabs but this new finding could help sharpen the search even more.

Between last October and Aug. 7, 782 were captured at Makah Bay. They’re reported to be from multiple year classes and ranged in size from 1 inch to over 3 1/4 inches.

According to a Sea Grant map, specimens have also been found to the east at Dungeness Spit and Discovery Bay on the north Olympic Peninsula; Westcott Bay on San Juan Island; Fidalgo, Padilla and Samish Bay’s in Skagit County; and Lagoon Point on the west side of central Whidbey Island.

Researchers theorize that the inland green crabs are coming from a source population somewhere on the outer coast of Washington, Vancouver Island, Oregon or elsewhere.

They say it’s more likely that “reversal” current conditions pull larvae into the Strait of Juan de Fuca from the Pacific than that juveniles from a population in the Sooke Basin of Vancouver Island have dispersed across the channel.

The Makah colony represents the largest concentration so far found in Northwest Washington waters.

LORENZ SOLLMAN OF THE U.S. FISH AND WILDLIFE SERVICE INSPECTS A TRAP SET OUT TO COLLECT INVASIVE EUROPEAN GREEN CRABS AT DUNGENESS NATIONAL WILDLIFE REFUGE. (ALLEN PLEUS, WDFW)

The worry is that if green crabs establish a sustaining population in Puget Sound, they could damage eelgrass pastures — so important for our salmonids and other fish — and clam beds.

Efforts to remove them are being led by state, tribal, university and federal agencies. They’re focusing on monitoring bays, estuaries, spits and other water features and rapidly responding to discoveries.

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