New England Fisheries

Clam Dredging: A Path of Destruction

The E.S.S. Pursuit in New Bedford Harbor. Image via NOAA.

To the right is an image of the 145’ offshore clam-fishing vessel, the E.S.S. Pursuit, in the harbor of New Bedford, MA. Those heavy steel boxes connected to the stern are hydraulic dredges that are used to fish clams by dragging them along the ocean floor behind the vessel.

Highly pressurized water is blasted from the ship and downward from the front end of each dredge to “liquify” and suspend the sediments in front of it, dislodging clams – and whatever else is embedded in the sediments – and catching them in the body of the dredge for retrieval back onto the ship.

In 2010, the pictured boat, based out of New Jersey, was confined to port because it had inadvertently dredged up several canisters of a poisonous chemical during one of its trips out at sea. Consequently, many of the crew and clams were exposed to the toxin. The injured crew were medically treated, and the contaminated shellfish were disposed of at an incinerator as hazardous waste.

I bring up this frightening chemical incident involving the E.S.S. Pursuit because the clam industry has made a number of claims about the “benign” nature of this fishery. It has done so with the hope that the fishery management council and NOAA Fisheries will allow the offshore clam fleet to continue to fish, by exemption from other regulations, in areas that the Council has identified as having some of the highest habitat benefits for New England fish species.

Healthy Skepticism

The claims are based on the premise that these dredges only operate in high-energy sandy areas of the ocean where strong currents or storms already naturally produce a heavily disturbed evironment that is only suitable for clams or other marine life that have evolved to thrive in such conditions. Industry representatives further claim that their equipment cannot function properly in areas where there is cobble, rock, or other large debris.

Accordingly, no one need worry that these destructive dredges might inadvertently stray into cobble or rock habitats where everyone concedes the dredges would destroy the resident flora and fauna and have long lasting negative impacts on the surrounding environment. Right?

I’m not convinced. If the unfortunate chemical incident is any indication, these dredges are quite capable of capturing large metal canisters and dragging them back up to the ship without any problem. Cobble or rock, by contrast, would seem to be of little consequence to their operations.

The industry also claims that the impacts of dredging are so insignificant and temporary, that immediately after dredging an area, it’s impossible to even know that it had been dredged. Fishermen and citizens on outer Cape Cod, where hydraulic clam dredges are used, are rightfully skeptical.

Local divers have documented the persistent trenches and instability that clam dredges have created off the Cape, cutting through ecologically critical eel grass beds and leaving a path of destruction. These are areas that the Commonwealth of Massachusetts has identified as high-energy areas, and yet the evidence of the impacts of this inshore dredging are impossible to avoid.

As with most fisheries, there are times and places where commercial fishing can be profitable and sustainable, and where technologies like hydraulic clam dredges can be used appropriately, without collateral impacts. And there have been a number of studies concluding that other types of gear, like otter trawls and scallop dredges, likely cause more damage than gear used by the clam industry. Even so, this gear is not benign. The dredges are designed to totally disrupt the sea floor and anything near it. Moreover, any claims that vessels can maneuver around varying sediment areas with surgical precision are ludicrous. Before  exceptions are allowed for use of this sort of bottom-altering gear, the industry should bear the heavy burden of demonstrating that its claims are true. These vessels already have access to vast tracts of clam-bearing ocean floor. It seems like that should be enough.


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