BUCKSPORT — By now, it is no secret that the Portland-based company Whole Oceans plans to build a land-based fish farm on the site of the former Verso mill that will, if all goes as expected, grow 20,000 metric tons (about 44 million pounds) of Atlantic salmon using recirculating aquaculture system (RAS) technology.
Last week, about 30 people attended a Tuesday evening “pop-up” at the Bucksport Performing Arts Center, hosted by the Maine Science Festival, where scientists from the University of Maine and the U.S. Department of Agriculture’s National Cold Water Marine Aquaculture Center in Franklin explained just what RAS aquaculture is and how it works.
Jennifer Fortier, an outreach and development associate at Whole Oceans, brought the group up to date on the company’s projected permitting and construction schedule.
An RAS operation, Michael Pietrak, a research scientist at the Franklin facility explained, is very much like a home aquarium (a mini-RAS) but on a giant scale.
A good-size home installation might incorporate a 50-gallon aquarium. The proposed salmon farm in Bucksport will start out with 36 grow-out tanks each holding some 450,000 gallons. There will also be dozens of smaller tanks where salmon eggs will be hatched and juvenile salmon will grow progressively larger before moving to the big tanks.
Small or large, Pietrak explained, RAS installations must monitor and control the same factors — water temperature, amount of oxygen in the water and pH (acidity) — among them, the fish must be properly fed and waste products removed from the water and safely disposed of.
In a large RAS installation, all of those parameters are monitored constantly and automatically. Fish receive precisely measured amounts of feed on a predetermined schedule — often using robotic feeding machines.
As the name suggests, all RAS installations rely on maintaining a constant amount of water in the system but adding only small amounts of new water on a regular basis.
To accomplish that, the water regularly circulates through elaborate filtration that removes solids — fish waste products and uneaten feed — and uses bacteria to convert ammonia excreted by the fish into harmless nitrates and ultraviolet or other treatment to kill any pathogens in the water before it recirculates into the system.
In large, commercial systems, any sludge is dewatered and then disposed of — as compost, biofuel or for some other purpose.
The new, replacement water that comes into the system is also extensively monitored and filtered to prevent the introduction of any unwanted elements, pathogens or biological threats — such as the sea lice that can infest salmon that grow in the wild — from entering the system.
Biosecurity is critically important for any aquaculture operation, especially an RAS facility, Ian Bricknell, a professor at the University of Maine’s School of Marine Science, told the audience.
Properly practiced, good biosecurity measures can eliminate the introduction of “novel organisms” such as disease-causing pathogens into a system that is conducive to their spread.
Disease can spread from infected fish to their offspring by the mixing of healthy and diseased fish or the introduction of pathogens into the system.
In ocean fish pens, Atlantic salmon can be exposed to naturally occurring pathogens and sea lice. That problem can be eliminated in an RAS where the water is filtered and monitored as long as there adequate biosecurity measures in place.
That’s why workers are required to wade through disinfecting foot baths before entering a facility and why it is important to make sure no possibly contaminated equipment comes into contact with the fish stocks.
Good biosecurity has the obvious benefit of keeping fish healthy and the system more productive, Bricknell said, but there is a second benefit. No pathogens or invasive organisms will escape into the natural environment from a well run RAS.
“The ocean is full of disease” affecting fish, Bricknell said. “On land, there is much more control and much less disease.”
While most farmed Atlantic salmon are still grown in ocean net pens, the cost differential between pens and land-based RAS has diminished in recent years, Fortier said.
Although net pens “will probably always be a little cheaper,” RAS can grow a fish that is “secure and traceable from egg to plate in one facility,” something consumers find increasingly important.
While Whole Oceans is still months away from beginning construction — as of last week it had yet to sign a final purchase and sales agreement for the former mill property — the company is still hopeful that work will begin in the spring. In part, that depends on when the company completes its permitting process with the Maine Department of Environmental Protection.
Whole Oceans has received approval of its application for a wastewater discharge permit but must still obtain at least two more environmental and site development permits from the state. Those permit applications seem to be in good order.
“Bucksport is the perfect location for us,” Fortier said.