Finfish aquaculture involves holding fish, either in seapens or in lab-based tanks, where they are fed specially created feed that is often a mixture of smaller ‘bait fish’ or a mix of fish and vegetable protein. In Maine, Atlantic Salmon is the only finfish being grown in an ocean-based aquaculture setting. There are multiple proposals for finfish to be raised in land-based tanks in what is referred to as a recirculating aquaculture system (RAS), specifically raising yellowtail in Jonesport by the company Kingfish Zeeland, and there are also land-based aquaculture proposals for salmon in Bucksport by Whole Oceans, and Belfast by Nordic Aquafarms (Belfast town website with over 100 information links here).
Because there are human inputs into the water in a finfish aquaculture system, there are additional permitting rules, in particular around water quality. These concerns include nutrient pollution from either uneaten food, antibiotics used to treat disease, or from the high rate of excretion of these concentrated fish operations.
Finfish, and specifically salmon aquaculture, has a limited history in Frenchman Bay. In the late 1980’s Erick Swanson started The Penobscot Salmon Company to raise Atlantic salmon in pens in Frenchman Bay, later called Atlantic Aquafarms and then Atlantic Aquafoods but this effort only lasted a few years and stopped by the mid 1990’s. After that there was a short-lived attempt to raise cod in pens by Great Bay Aquaculture, but that also was a short-lived activity.
One of the problems they occurred in salmon aquaculture in Frenchman Bay was mortality of fish due to a phenomenon that is called super chilling. The added salt in seawater means that it freezes at a lower temperature, 28.4 degrees farenheit (-1.8 degrees centrigade) for full-strength seawater. Unfortunately, salmon, like most animals (including humans), have an internal salinity of about 1/3 seawater, so the liquids in our cells freeze, but at a temperature between the freezing point of seawater and freshwater (about -0.7C or 30.7F). In the winter, if surface seawater gets very cold, possibly because the area is near a shallow inshore area, the outgoing water can pass through a seapen and cause mass mortaility of fish when their body fluids begin to form ice crystals. Such an event happened at multiple salmon farms in Nova Scotia in 2015.
As of the end of 2020, there is no finfish aquaculture in Frenchman Bay, but American Aquafarms is in the first stages of data collection and discussions with state regulators and the community for two large sites with salmon in sea pens in Frenchman Bay, A list of links to articles and other information about that specific proposed salmon sea-pen aquaculture system is here.