Seal predation at salmon farms in Maine, an overview of the problem and potential solutions

Salmon aquaculture facilities in Downeast Maine are occasionally attacked by harbor seals and gray seals. The predators kill and injure valuable fish and may damage net-pens allowing farm-fish to escape. Industry proponents claim up to 10% of the industry's farmgate value is lost to seal predation. In addition to financial impacts, the escapement of cultured fish may pose a threat to indigenous Atlantic salmon stocks. Salmon growers in Maine employ a variety of predator control measures-netting systems, underwater acoustic devices and pyrotechnics-but no battery of protections seems to be 100% effective. In the past, those seals who could defeat deterrence strategies would be targeted for lethal removal. Recent amendments to the Marine Mammal Protection Act (MMPA), however now prohibit the killing of depredating seals. This paper provides an overview of the problem, surveys technological and non-technological solutions and mitigating measures, and describes the work of a stakeholder task force convened by the National Marine Fisheries Service to investigate the matter.