Thank you for bringing attention to the dramatic decline of Casco Bay soft-shell clam populations with your front-page story “Survival in the flats” (May 1).
Prompted by the warnings of concerned clammers, as well as actions taken by the town of Freeport, the Downeast Institute for Applied Marine Research & Education initiated its Freeport field research in 2014.
During 2014-2015, we conducted 13 distinct large-scale field experiments at 41 different intertidal sites, as well as green crab trapping in the Harraseeket River. We utilized fencing, nets, wooden boxes and sediment buffering in our efforts to protect clams. Each year, our research questions and designs build upon the previous year’s findings.
This year, we are conducting six separate field trials at 30 sites in Freeport, and are deploying 840 protective boxes to encourage wild clam recruitment, 175 clam cages to grow hatchery seed to commercial sizes, and 40 predator exclusion nets to continue collecting data on effects of predation.
Experiments include exploring bioremediation to reduce milky ribbon worm predation, and we continue to examine the relative importance of predation vs. coastal acidification on wild clam recruitment.
The data we have collected since 2014 show clearly that predation (mostly by invasive green crabs, native sand crabs and ribbon worms) is the No. 1 problem facing Casco Bay clams and is most likely the cause of the substantial drop in landings. (See downeastinstitute.org/freeport.htm for more information.)
Presently, shellfish managers should consider the effects of coastal acidification and other purported stressors to be secondary in importance in explaining the current depressed state of the soft-shell clam resource, and to adapt their management strategies to this new reality.
Continued research is needed, and we encourage regulators, policymakers and funders to prioritize securing the future of this economically and culturally important fishery.
Brian Beal, Ph.D.
professor of marine ecology, University of Maine at Machias; director of research, Downeast Institute
Machias
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