Salmon pen floats under construction on a beach in New Brunswick, Canada.© Colin Woodard
"We wanted to see if it was possible to farm fish and shellfish offshore, in an extreme environment like the Gulf of Maine," says Richard Langan, director of the University of New Hampshire’s Open Ocean Aquaculture project, which is also raising halibut, mussels and sea scallops in sunken cages. "Now we know we can and that this is just the beginning for this type of aquaculture."
As many of the world’s most important commercial fish populations have collapsed, fish farms have stepped in to fill the void. Farmed salmon, shrimp and mussels are now cheaper than their wild-caught competitors in many markets, and researchers say that may soon apply to cobia, halibut, cod and other fish the sea once produced in prodigious quantities on its own.
But the fast-growing industry has also triggered some environmental problems. In Asia, shrimp ponds destroyed vast swaths of mangrove forests, the key nursery habitat for many undersea creatures in tropical waters. In North America, coastal salmon farms fell into public disfavor as they became implicated in both algae blooms (fed by fish feces) and the further decline of wild salmon runs (due to competition and interbreeding with escapees from the farms). Both industries suffered enormous losses from disease outbreaks like infectious salmon anemia and Taura syndrome in shrimp.
Now, however, the marine aquaculture industry appears to be solving many of its own problems. Norwegian salmon farmers vaccinate their fish, eliminating the need to dump antibiotics into crowded surface pens. Canadian researchers are developing promising ways to eliminate nutrient pollution from New Brunswick farm pens by growing salmon alongside mussels, which filter the wastes. In Florida, scientists are growing marine shrimp in zero-discharge freshwater ponds located miles inland, eliminating damage to coastal habitats.
"Aquaculture producers are doing everything they can to make sure they are a non-polluting industry with a high-quality product," says Leroy Creswell, a past president of the World Aquaculture Society. Creswell heads the University of Florida team that is growing shrimp in ponds filled with mineral-rich groundwater, 10 miles from the sea. "Unless you’re raising shellfish, you’re just never going to get a permit to raise fish right along the coastline in the U.S.," he adds. "As a result the industry is going in two directions: inland or offshore."
Moving pens offshore and beneath the surface may solve many of the industry’s worst problems, as long as they are sited properly. UNH’s experimental farm is located in water nearly 200 feet deep with strong currents that disperse feces from the four fish cages; after five years of careful monitoring, Langan says there has been no detectable changes in nutrient levels in either the surrounding water or the sediments on the seafloor. He also says there hasn’t been a single escapee. The cages appear impervious to seals, which cause considerable damage to floating salmon pens.
"The environment is something we have taken very seriously from the beginning," Langan adds, standing beside a 20-foot-tall steel food buoy in UNH’s cavernous ocean engineering lab. "We’re a small operation now and we’re very interested in seeing at what scale you would start seeing deposition [of feces] on the seafloor or changes in the seawater."
Those may not remain theoretical concerns for long. In June, the Bush administration introduced legislation that would allow the Secretary of Commerce to issue permits for commercial aquaculture farms in federal waters, which are generally between 200 and 300 miles from shore. The Commerce Department wants to expand the U.S. fish farming industry fivefold over the next two decades.
Critics are concerned with the draft legislation because it lacks specific environmental rules, giving the administration wide discretion in issuing permits. "The legislation is way too open-ended, allowing the Commerce Secretary to issue a permit even if the environmental impacts are substantial," says Rebecca Goldburg, a senior scientist at Environmental Defense in New York.
Goldburg says cod and other fish may spawn inside cages, releasing fertilized eggs that will escape into the wider environment, possibly contaminating wild stocks. She agrees that pollution will be greatly reduced by stationing farms offshore, but is concerned that farms will tend to aggregate for economic reasons, possibly leading to degradation.
In Alaska, where offshore fishing remains a major industry, the Republican-controlled legislature quickly passed a resolution opposing the plan. "The global fish farming industry is bad news for Alaska and for fishermen nationwide," said co-sponsor Bill Thomas. "In Alaska, we produce seafood the way it should be done, and we will fight for the well-being of our industry and our communities."
Offshore farming may be fine in principle, but only if it’s managed correctly, concludes the group Seaweb.