Green Crab Invasion Mitigation

Green Crab Invasion Mitigation

Invasive Green crabs have declared a war on Maine’s aquatic habitats, and right now they are clearly winning. Thousands of acres of aquatic habitat have been wiped out with species such as eelgrass beds, lobster, and shellfish under attack. We are now seeing mass migration of lobsters away from the shallow coastal regions into deepwater channels. While scientists and certain non-profit organizations continue to blather on about ocean acidification and it’s impacts, the “dumb” clammers are left to wonder about impact that the complete removal of thousands of square miles of filter feeders has had on the ocean’s ability to cleanse itself from polluted run-off. And even these certain scientists and non-profits predictions about ocean acidification are true, those predictions won’t matter when there is nothing left to worry about in our oceans except for invasive green crab.

Maine’s Marine Resources are in the 59th Minute:

Maine clammers have been witnessing the staggering growth and scope of the invasion and recognize that we are now in the 59th minute of the invasive green crab’s exponential growth and are about to lose all our coastal resources to this invasive predator.

Although the odds are staggering, the Maine clammers are not going down without a fight, as we believe we have a moral imperative to do what ever it takes to stop the total loss of Maine’s shellfish resources. To this end, the MCA is working in collaboration and defiance to educate Maine’s coastal populations about the invasive green crab devastation and what we can do to carve out a healthy, sustainable future.

5 to Stay Alive Trapping Program

MCA founded and manages the 5 to Stay Alive invasive green crab trapping program. In general, this program encourages people, and expects our fellow marine resource stakeholders to find a way to incorporate into their work schedule a system of being responsible to fish 5 green crab traps. Invasive Green Crab traps can be found at Pono Trap Co. and Brazier Trap Co. (in Waldoboro). We are already seeing innovative ideas and designs being put forth by clammers and fishermen in different coastal regions.

Pulling an Acer Crab Trap built and designed by the MCA’s Ace Simmons and Russell Brazier of the Brazier Trap Company. Photo courtesy of The Forecaster.

Pulling an Acer Crab Trap built and designed by the MCA’s Ace Simmons and Russell Brazier of the Brazier Trap Company. Photo courtesy of The Forecaster.


As part of the partnership with the town of Freeport to identify invasive green crab mitigation techniques, MCA recently designed and installed the biggest invasive green crab fencing project in the history of the state in Casco Bay. Fencing is the only known effective tool to limit invasive green crab access to intertidal shellfish resources. Clammers designed and installed over 3,000 ft. of the 18-inch tall mesh, wood, and aluminum fencing. Due to the physical requirements of installing in the soft bottom clam flats, clammers are the only people capable to do large scale fencing projectsThe fencing project in Freeport is multi-faceted with 6 30×30 non-vented control areas and one vented


2,000 ft stretch of fencing. The MCA looks forward to working with agencies such as Army Corps of Engineers (ACOE) and National Marine Fisheries Service(NMFS) so they can better understand the need for adaptive application of certain regulations. For example, in Freeport’s recent application to the ACOE, it was clear during that process that the federal regulators had no true on the ground understanding of the ecosystem. Requiring a high number of vents (breaches) to protect sturgeon that all the fishermen know don’t frequent or in habitat the bays of Freeport is a good example of the absurdity of inflexible rules. The problem is that federal rules require protection of certain species, but to just protect one species at the expense and health of all the others is irresponsible.

The Freeport Shellfish Commission has been the model in the last decade in applying more modern management tools that have been successful in increasing the volume of shellfish harvested and maximize the value of the resource. The goal of Freeport’s program is to reduce the predation that is responsible for the complete depletion of 80% of the once productive clam flats, which is estimated at approximately 700 acres out of 800 acres. Read more about the project with the town of Freeport.

Scientific Research:

MCA has assumed the responsibility of providing the necessary manpower and logistical support needed to construct, install, and remove 3,000 ft of fencing in Freeport’s intertidal flats.

Through strategic partnerships, MCA has been collecting size, sex and distribution information of invasive green crabs. Our partners include the town of Freeport, Resource Access International, and the DownEast Institute of Applied Marine Research and Education. Information collected is already providing Maine’s Municipal Shellfish Programs with information on how to best prioritize the application of scarce resources to battle the green crab invasion. For example, through the Freeport trapping program we have learned that trap location and the ability to keep traps baited are the most critical factors for successful trapping. Through this research we have learned to put the traps as close as possible to the soft shoreline and the marshy invasive green crab burrows as possible. Also to keep the traps fishing for a full 24 hours it is necessary to place traps in the channels adjacent to clamflats, as this is here crabs retreat during the daytime hours and during lowtide. Other important information that we have picked up so far is that in order to have any possibility in reducing invasive green crab population, that the off-season winter months should be a priority in trapping. It is much more difficult to fight crabs in the summer, because they are spread out amongst the flats. However, in the winter the invasive green crabs are concentrated in the deep water channels, aka the invasive crab’s deep water “winter resort”.

Additionally, MCA has developed, in collaboration with student clammer and Colby College student “Thorgaard” O’Neil, a study to look at the effect of invasive green crab trap soak time on catch rate.

Freeport Research on the Decline of Soft Shell Clams:

The town of Freeport has begun a historic effort to address the rapid disappearance of soft-shell clams. It’s the first comprehensive, large-scale research project in Maine to study the impact is of invasive green crabs and ocean acidification caused by global warming. This is also the largest ever financial allocation by a town to conduct a shellfish research project. This action taken by Freeport demonstrates the commitment of the town to the shellfish resource and clearly establishes them as the leader in the state in both recognizing the changing climate and moving ahead with adaptation techniques to keep it’s local industry and culture alive.

Exploration of Alternative Uses of Invasive Green Crabs

MCA is fully behind DMR Commissioner Pat “Problem-Solver” Keliher in his policy of being very careful when considering a market for green crabs. The ProblemSolver’s position is these are invasive species and they don’t belong here, so we don’t want to start a commercial fishery. The MCA is very cautious when talking about creating a market for invasive green crabs or any other invasive marine species. We do not want a “sustainable” for invasive green crabs. Invasive Green crabs are edible, however our experience that it is very difficult to extract their small amount of meat and thus far they have proven to be difficult to move as a food source. There are studies underway at the University of Maine to determine alternative market outlets, for example as pet food and fish food. Another promising potential use for the invasive green crabs is grinding them up for a high quality organic fertilizer.