The European green crab (Carcinus maenas), an invasive species first detected in Ne w England in the early 1800s have had a wide range of negative impacts on local ecosystems, including reducing native bivalve populations through predation, outcompeting native crustaceans for food and shelter, destruction of eel grass habitat and subsequent changes to fish community structure. Increases in green crab abundance and predation have also been linked to the recent decline of the soft-shell clam industry in New England. Compounding these issues is the link between increasing green crab abundance and increasing ocean temperature, which has had severe ecological and socio-economic consequences in the Gulf of Maine, which is warming faster than 99% of the world's other oceans.
Some New England states have either implemented mitigation measures to keep population levels at bay including bounty programs (MA) or developed techniques to diminish the effects of green crab predation on wild and hatchery reared juvenile soft-shell clams (ME) . In Canada , the Department of Fisheries and Oceans suggests that a green crab fishery may be a viable way to control population abundance and derive value from this invasive species. Existing fisheries in the U.S. and Canada target green crabs for lobster and whelk bait, but a higher retail price is necessary to encourage expanded fisher effort and new participation . Therefore, as a way to mitigate green crab populations, engage and increase fisher participation, develop a potentially new aquaculture industry and create a high value, high quality, culinary product, we have been exploring techniques and market feasibility for soft-shell green crab in New England.
As with traditional soft-shell crab production- we collected green crabs in the 'pre-molt' phase of the molting cycle from the wild population during peak molting times. These 'pre-molt' crabs were identified by subtle color changes on the margin of the abdominal episternites of the crab (morphological indicators were determined independently from past research by the PI, researchers at the University of Prince Edward Island, Canada and Manomet, Inc., with assistance from Venetian fishermen). Pre-molt crabs were then held/stored individually until they molted or for 21 days in: a) Floating crates , b) Plastic containers in large flow through tanks , c) Wire mesh 'crab condos' in large flow through tanks or , d) Recirculating, modified salmon egg-tray incubators at different temperatures.
The results of this work over a three-year period, suggest that molt success is dependent on a combination of factors (e.g. temperature, salinity and how advanced in the molting cycle the crab is ) and the most economic and time efficient method for soft-shell green crab production is wild harvest of advanced pre-molt crabs held in compartmentalized wire mesh 'crab condos' in large flow through tanks.