Pilot Project Supports Green Crab Removal in Wellfleet Harbor

A 16-week experimental pilot project to harvest green crabs in Wellfleet Harbor has launched, targeting the invasive crab species.

According to a Provincetown Independent report, Wellfleet shellfisherman Dave Seitler and Owen Nichols, director of marine fisheries research at the Center for Coastal Studies, are collaborating on an effort to harvest green crabs from the harbor by collecting them in traps set at locations such as Blackfish Creek, Chipman's Cove, and the railway bridge. 

The two began the initiative on May 15 and are using 35 baited shrimp traps. The traps have been modified to have smaller entryways, thereby avoiding the snaring of terrapin turtles.

Seitler received a $5,000 grant from the Wellfleet Oyster Alliance to purchase the modified traps in March from a lobsterman in Nobleboro, Maine. Each trap is identified with a white buoy, and Seitler inspects the traps once a week. Then, he and Nichols count and weigh what's collected in the traps before analyzing their catches.

“We're looking at the sex ratio — whether we're catching more males or females — what size the crabs are, what condition they're in,” Nichols explained to The Provincetown Independent. The pair are also determining whether and when the female crabs carry eggs. 

“If you want fewer crabs, you might want to harvest them during a time when they're reproducing,” Nichols said.

European green crabs pose a different threat to salt marsh habitats than Sesarma crabs, known as purple marsh crabs, that eat Spartina reed grasses in marshes, including the marsh in Provincetown's West End.

As the green crabs tunnel underground to dig up clams, they uproot soil and sand in the process. Two studies conducted so far suggest that green crabs are particularly harmful to small oysters growing in shellfish nurseries, which are still too small to be harvested.

Wellfleet Shellfish Constable Nancy Civetta said that efforts to control the green crab population have been few and far between until now. Civetta hopes that removing the crabs from the estuaries would benefit the wild oyster population and promote survival for the salt marshes.

Contrary to their name, green crabs are not always green. According to NOAA Fisheries, the top of the crab's shell may appear mottled dark brown to dark green, with small yellow patches. The bottom of the shell may be orange or red when the crab is molting. Green crabs have a distinctive shell shape; adult shells can measure up to 4 inches across.