Pollution
Untreated fish waste, excess feed and dead fish empty directly from cages into the ocean. This waste has been shown to alter fragile marine habitats. It is unknown how the oceans, which have already been damaged by industrial and agricultural pollution, and more recently by the catastrophic oil spill in the Gulf of Mexico, will respond to yet another source of pollution.
“Little is known about the assimilative capacity of the marine environment for these pollutants,” concludes a 2007 report commissioned by the Woods Hole Oceano-graphic Institution. “Pollution from a greatly expanded industry could have significant effects locally and regionally.”
The most recent edition of the Congressional Research Service’s report on open ocean aquaculture makes a similar point, noting that “The present lack of knowledge – owing to limited experience, lack of research funding, and few studies focusing specifically on open ocean aquaculture – limits under- standing of potential environmental concerns.”
Although we do not know the full extent of the damage that can be caused by offshore aquaculture facilities, what we do know does not present a pretty picture. A 2011 study accepted to the journal Marine Environmental Research analyzed the impacts of marine aquaculture on a large scale. Researchers found that aquaculture facilities were responsible for an increase of nutrients (or pollutants) in a gulf of the Italian Coast and wrote that “off-shore aquaculture may affect the marine ecosystem well beyond the local scale.”
Antibiotics, pesticides and the other drugs or chemicals used in these operations can also be damaging. As with waste, little is known about how these drugs might affect the offshore marine environment, because the drugs that might be allowed on factory fish farms have not been tested in open ocean marine farming situations. Evidence does indicate several serious concerns associated with the use of aquaculture drugs.
For example, Maine lobsters have been harmed by pesticides used to control sea lice in salmon farms along the Maine and Canadian coasts. Further, antibiotics can kill beneficial sea floor bacteria and spawn antibiotic-resistant organisms. One study found that the use of antimicrobials on fish farms can lead to the creation of reservoirs of drug-resistant bacteria. According to the study, the genes responsible for this resistance may ultimately affect the human population through transfer to human pathogens.
Disease
The drugs mentioned above are used to overcome the increased risk of disease that exists when fish are packed densely together in operations, are exposed to pathogens in the marine environment and are subject to a number of other environmental stressors.
Sea lice is perhaps the most notorious of aquaculture infestations, thriving in the presence of new hosts, such as with the expansion or addition of a fish farm. According to a 2011 article, exposure to salmon farms with lice infestations may result in a “sharp decline” in wild pink salmon populations in British Columbia’s Broughton Archipelago. In addition to sea lice, Infectious Salmon Anemia (ISA) has been a major problem for salmon farms. The disease was reported first in Norway, and later spread to Canada, Scotland, the Faroe Islands and the United States. Around 2007, the virus wreaked havoc on the salmon industry in Chile — devastating production and putting more than 7,000 people out of work.
Disease has also been a problem for open ocean aquaculture facilities in the United States. In Hawaii, for example, Kona Blue Water Farms has encountered problems with skin flukes, a parasite that does not harm human health but must be controlled due to its negative impact on the fish. The company also has dealt with streptococcus infections, which it treated with the antibiotic florfenicol, a drug that has not been tested specifically for aquatic use in Hawaii’s unique marine environment.
Escaped Fish
Fish escapes are a major problem on open water fish farms. They can be caused by equipment failure, staff error and adverse weather conditions. Fish raised in aquaculture facilities are bred to thrive in farmed, rather than wild, environments. When escaped fish interbreed with wild fish, their offspring may have diminished survival skills, resulting in a genetically less fit wild fish population.
The recovery of wild salmon populations has been jeopardised by farmed salmon escapes. These escapees can interbreed with wild salmon and may harmfully alter the genetics of the wild stocks. The international list of escape disasters is extensive: About two million farmed salmon escape into the North Atlantic each year, an amount equal to the number of wild salmon in the region.
In six months of 2007 alone, more than 100,000 Atlantic salmon escaped from four facilities on the west coast of Scotland. On 31 December, 2008, storms caused 700,000 salmon and trout to escape from various farms in Chile, prompting the leader of the Chilean Senate’s Environmental Committee to proclaim the incidents an “environmental disaster.”
In October 2009, 40,000 salmon escaped from a farm in British Columbia. One year later, 70,000 salmon escaped from a farm in Norway. And not all instances of escape occur so far from home. In 2010, an article revealed that a research project in the Bahamas, headed by University of Miami researchers, experienced a loss of approximately 90 per cent of its fish. Fifty-six Kona Blue Water Farms in Hawaii also has encountered ongoing instances of escapes.
The negative impacts of escaped farmed fish can be even more serious if the fish are non-native or have been genetically modified. California, Maryland and Washington have addressed this by banning farming of genetically modified fish in their state marine waters.
Pressure on Wild Fish
Although one might assume that farming fish could take the pressure off wild stocks, this is not actually true. Farmed fish often are fed large amounts of feed made from fishmeal and oil. These ingredients are derived almost exclusively from small ocean fish such as sardines, anchovies and herring, caught in mass quantities in the Northeast Atlantic and off North and South America’s Pacific coast. The aquaculture industry is the largest user of fishmeal and oil, and the amount demanded continues to increase.
In 2006, an estimated 3.72 million metric tons of fishmeal were consumed, representing 68.2 per cent of worldwide production and 0.84 million metric tons of fish oil, or 88.5 per cent of production. Many species of small fish being converted to aquaculture feed are being harvested beyond sustainable levels, not only leading to their depletion but also jeopardizing the predatory in fish that depend on them for survival, such as tuna, salmon, grouper and snapper.
Impacts on Marine Animals
Open ocean aquaculture facilities could negatively affect the marine animals that frequent these sites, including whales, seals, dolphins, turtles and sharks. Dolphins have frequented the site at Kona Blue Water Farms (see page 16), and the animals have apparently begun to exhibit “unnatural behaviors,” which may constitute conditioning. If the animals have become conditioned to respond to feeding opportunities at the site, they may experience reduced survival skills. An investigation of sharks and ocean-farming cages in Hawaii has found that sandbar sharks tend to aggregate around the cages, and that tiger sharks occasionally visited. Although the study concluded that the sharks were not affecting public safety at beaches adjacent to the cages, the researchers noted that the ecological effects of aggregating sharks are unknown.
November 2011