But a nondescript building, down the street from the shopping malls of Portsmouth, New Hampshire, is teeming with cod in all stages of life. Swimming in salt water tanks under the roof of the GreatBay Aquaculture company, these fish hold the promise of giving a new boost to the Gulf of Maine's failing cod supply. Pinkish-gray, gape-mouthed cod, captured from the wild, are parenting new generations of fish that will begin their lives in the on-shore hatchery and grow to adulthood in ocean cages.

GreatBay is the first commercial hatchery in the United States to produce juvenile Atlantic cod for the aquaculture industry. The hatchery also produces summer flounder, which are mainly sent to customers in Asia and Mexico. After farming cod for about four years, some of GreatBay's fish have already been sold on the Chinese market. In February, GreatBay's main customer, Cooke Aquaculture of New Brunswick, took its first cod harvest from the Bay of Fundy from cages near the Deer Island ferry terminal.

Commercial cod farming began in Norway, but the technology is relatively new to North America. As with salmon aquaculture, critics fear that cod farming will bring environmental risks. But in raising the cold water fish, GreatBay is keeping close ties to the research community and using technological innovations in an effort to farm responsibly. The company aims to steer clear of the problems that have plagued other aquaculture operations and led to impacts on the ecosystem from escaped fish, disease and pollution from nutrient loading.

Selective breeding

The goal for the hatchery managers is to produce fast-growing fish, said GreatBay co-founder Chris Duffy, using selective breeding, rather than the more controversial genetic modification. If genetically modified fish escape from their pens they can compete with wild fish stocks for food and habitat, as occurred among salmon in the Gulf of Maine in recent years.
“We're staying away from that area,” Duffy said, explaining that the company feels a responsibility not to run the risk of unleashing genetically modified fish into the environment.

GreatBay breeds wild cod, monitors their offspring and selects those that grow fastest, so that the farmed fish are not genetically different from wild stocks. The company is partnering with academics and two other commercial aquaculture companies in Canada to find ways to improve cod growth and better understand their genetics.

GreatBay's facility houses two groups of adult cod that naturally spawn at different times of the year - winter and spring - and provide stock for the hatchery. The eggs released in the spawnings are less than one millimeter long and barely visible to the naked eye. Like tiny transparent bubbles, they float in incubating bins for two weeks. When they hatch, the larvae go into a large tank where they live for two months. There they get their first live meal of rotifers, microscopic invertebrates fattened on algae and nutritional enrichments.

“The first feeding of an organism is the most important,” Duffy said. He added that it is complicated and doing it successfully is “what makes a hatchery work.”

As they grow - eventually becoming about as large as the tip of a fingernail - the larvae also eat brine shrimp. Ultimately, the young fish are fed a dry diet. When the juveniles are big enough, they can be transported to cages in the ocean for grow-out.
One group of fingerlings (juveniles weighing about 15 to 20 grams) now at the hatchery will be moving to the University of New Hampshire's cages about five miles offshore near the Isle of Shoals this spring.

Disease prevention

Controlling disease among fish living in close quarters is another challenge for the hatchery managers. When he first started fish farming, Duffy said, “I thought disease was like a bomb waiting to go off.”

Now, he believes that providing fish with a healthy, stress-free environment helps to prevent illness. Maintaining health involves “trying to figure out how to make fish more comfortable” and creating a stable environment for them, Duffy said.

Fish brought in from the wild are treated for naturally occurring parasites, since the parasites would bloom indoors, he said, but otherwise, the hatchery limits the use of medicines to prevent antibiotic-resistance from developing in the fish. So far there have been four treatment periods at the facility. GreatBay is also contributing to the development of cod vaccines.

Limiting pollution

With the encouragement of the U.S. Environmental Protection Agency, the facility is employing technologies to minimize the pollution that large concentrations of fish inevitably produce. GreatBay uses a recirculating system that draws water from the Piscataqua River and discharges back into it after the water is treated. Particulates in the wastewater, from uneaten feed and fish feces, are screened out with a drum filter and ultra-violet sterilization kills off bacteria. A heat exchanger allows for the transfer of heat from outgoing water to incoming, thereby reducing thermal pollution to the river and lowering heating costs at the same time.

In a greenhouse on-site, University of New Hampshire researchers are experimenting with using excess nutrients from the facility's waste stream to grow nori, the seaweed commonly used to wrap sushi. Nori grown in this way could potentially be used in fish meal, bringing on-shore fish farming nearer to a closed cycle, said Duffy, as some of the waste from the farm would get converted into feed rather than being thrown out.

© 2006 The Gulf of Maine Times