DV-16-10 Developing a fishery for softshell green crab by improving molt detection

Marissa McMahan
Northeastern University

Jonathan Grabowski
Northeastern University

Luke Poirier
University of Prince Edward Island

Jonathan Taggart
Venetian Fishery Partner

Fishing Industry collaborators:
Christopher Jamison, Georgetown, ME
Jim McMahan, Georgetown, ME
Herald Heald, Georgetown, ME

The invasive European green crab, Carcinus maenas, threatens two of Maine's commercially important fisheries: soft-shell clams (through predation) and lobster (through competition for shelter and food resources). The goal of this research is to develop a wild-harvest soft-shell crab fishery to reduce green crab populations while supporting a profitable bycatch fishery for lobster fishermen. While efforts to develop food products from adult green crabs have yet to be successful, a soft-shell product presents a new possibility, modeled after a traditional harvest of Moleche, Carcinus aestuarii, a type of green crab considered a delicacy in Venice, Italy. Venetian fishermen catch Moleche as bycatch, and are able to roughly determine how many days until the crabs will molt (i.e., shed their exterior carapace). With this knowledge, fishers can sort and store the crabs accordingly. In Italy, this supplemental industry generates around $15,000 a year for an individual fisherman.

The key to turning Maine’s nuisance species into a similar commercial catch is predicting when the green crabs are molting so they can be properly sorted and stored. With training from a visiting Venetian crab fisherman, McMahan and her collaborators successfully identified pre-molt green crabs, using subtle but distinct color changes on the ventral margins of the abdomen and platelets. They received additional Sea Grant funding to continue their work in 2017 (DV-17-03).