Environmental Impacts of Dredging
on Shellfish Aquaculture
Listed below are links to several articles describing the environmental impacts of mechanical harvest methods, or "dredging" in shellfish aquaculture.
The issue of dredging on fishing activity in general is quite inflammatory,
and a great deal has been published on wild harvest trawling impacts.
One author compared the impacts of trawling with those of clear-cutting (Baulch 1999), stating that
"trawling gear devastates the world's continental shelves."
Others describe "Watery Wastelands" devastated by trawling (Levy 1998). But in reality the
situation is more nuanced and requires an understanding of the various environments, different
types of gear, and how they interact. It is important to understand that the impacts of huge
heavy trawls operated in deep waters to capture wild fish or shellfish simply do not apply to
the operation of small dredges used inshore to harvest cultured shellfish on leased bottom.
There are many reports and reviews claiming little or no significant trawling impacts,
while others cite devastation and destruction. Some consider trawling to physically disrupt the
bottom and harm the benthic community by increasing sedimentation and predation exposure, and
reducing benthic primary production (Auster and Langton 1998, Bradstock and Gordon 1983, Brown 1989,
Collie et al. 1997, and Engel and Kvitek 1998). Conversely, others believe that trawling may mimic
natural disturbances and stimulate benthic production, thereby enhancing fish production
(DeAlteris 2000, MacKenzie 1982, Van Dolah et al. 1991, and Currie and Parry 1996).
A few review articles are worthy of special mention. Two of these provide an objective and
thorough review of the literature as it pertains to this issue: the 1995
Review of the Potential Impacts of Mechanical Harvesting on Subtidal and Intertidal Shellfish Resources
by Coen is a 46-page unpublished review of the impacts of hydraulic escalator dredges in South Carolina;
a similar literature review for Maryland
was published by Tarnowsky in 1996.
Robert Rheault's 2008 literature review of the subject was submitted as part of a Draft Environmental
Impact Study for proposed shellfish leases in Suffolk County, NY.
Mark Godcharles published the results of a study on the effects of a commercial hydraulic clam dredge
in benthic communities of several Florida estuaries in 1971.