Waste Contamination from Salmon Farms
Posted by Unknown in Aquaculture, Environmental Issues, Fish Farming, Pollution, Salmon, waste management, Water on Friday, 25 January 2013
(Pure Salmon Campaign)
Tens of thousands of farmed salmon confined to net pens produce a huge
amount of waste: chemical, biological, organic, and inorganic. For more
than 25 years, researchers around the world have recognized the harm
from salmon farm waste and its long-term impacts on water quality,
fisheries resources, and sea-bed ecology.
The Waste Problem
Salmon
net pens discharge untreated sewage, including contaminated feed laced
with chemicals, toxic residues, nitrogen, phosphorus, and copper and
zinc — not to mention diseases and parasites — directly into coastal
waters throughout the world. In addition, tons of contaminated salmon,
together with processing wastes — bones, entrails, and even the
carcasses of seals, sea lions, and other predators — are dumped in
landfills or processed for fertilizer or animal feed.
Sewer Systems in the Sea
Experts
have calculated that factory salmon farms, each extending over several
acres of coastal waters, discharge extremely high concentrations of
untreated sewage.
According
to Scotland's World Wildlife Fund, salmon farms there produce nitrogen
wastes equal to a human population of more than nine million people.
Even industry insiders concede that a typical 200,000-fish salmon farm releases:
- nitrogen equal to 20,000 humans,
- phosphorus equal to 25,000 humans, and
- fecal matter roughly equivalent to a city of 65,000 people.
In
2000 and 2001, nutrient discharges from aquaculture in the Northeast
Atlantic, including Scotland, Denmark, Norway, and Ireland, were
estimated at almost 40,000 tons of nitrogen and 6,600 tons of
phosphorus.
Pollution from Nutrients
Sewage and other wastes from salmon farming causes far-reaching environmental harm by:
- contaminating the sea-bed and its shellfish species,
- contributing to the antibiotic resistance of shellfish and wild fish, and
- causing eutrophication that triggers toxic algal blooms.
The
accumulation of sewage on the seafloor under and around salmon farms
directly harms marine biodiversity. Scientists in Scotland, Norway,
Ireland, and Canada have all shown that some of these effects may last
several years and extend for several hundred meters away from
salmonfarm. Divers have also found biological "dead zones" under salmon
farms — areas on the sea-bed devoid of marine life. This problem is so
prevalent that every few years salmon farmers relocate their net pens to
prevent the sea-bed from completely dying. As a result, salmon farms
are gradually moving further offshore and contaminating a larger area of
once healthy water.
Pollution from Chemicals
Salmon
farm sewage often contains chemicals and contaminants that easily enter
the food chain and accumulate as they move up it, ultimately reaching
humans. Among these chemicals are:- copper
- zinc
- tributyltin, a fungicide
- oxytetracycline and oxolinic acid, both antibiotics
- ivermectin, an anti-parasite compound
- emamectin benzoate, cypermethrin, azamethiphos tefl ubenzuron, and dichlorvos — all insecticides.
- polychlorinated biphenyls (PCBs).
The
abuse of antibiotics by large salmon farming operations has not only
led to chemical resistance in wild fish species but also raised health
concerns for humans whose diets already include milk, eggs, and meat
products containing unknown amounts of similar drugs.
Pollution from Mass Mortalities
Massive
farmed salmon deaths (euphemistically referred to as "morts" in the
industry) add to the burden of pollution from commercial salmon farms.
Industry-wide, mortality rates in factory salmon operations range from
10 percent to 40 percent. Outbreaks of infectious diseases, such as
Infectious Salmon Anaemia, may necessitate the slaughter of 100 percent
of a farm's stock, as it did in Scotland in 1998-99 when eight million
fi sh had to be killed to stem the spread of disease.
The
sheer volume of dead fish can only be measured in tons. In British
Columbia, for example, where factory farms produce 70,000 tons of salmon
annually, an estimated 20,000 tons of dead fish have to be discarded
each year. Globally, production of almost 1.9 million tons of salmon
produces a disposal problem for several thousand tons of dead and dying
salmon.
In
many parts of the world, thousands of tons of dead farmed salmon are
dumped every year in landfills. Because most salmon farms are in remote
locations, dead fish are often expediently dumped in isolated areas
rather than farmers paying to ship the waste to legitimate treatment
sites. In Scotland, for example, one company was caught dumping
thousands of disease-suspected farmed salmon on an environmentally
sensitive beach.
Alternative
disposal methods involve depositing fish in large silos and applying
chemicals to hasten decomposition. Dead salmon, some diseased and others
contaminated with chemicals, may also be used by farmers for fertilizer
or converted to compost and applied to farms and gardens. Still other
salmon "morts" end up in pet food or as feed on mink farms.
Closing the Net on Waste
Alternatives
to irresponsible dumping and waste discharge have been tried for
several years. Scotland's Environmental Protection Agency experimented
with various systems until the late 1990s when it yielded to industry
pressure and concluded that the cost of requiring new technologies was
"not viable for commercial salmon production under present economic
conditions." Similar studies in Canada, with treatments for waste water
from salmon farms, were also declared "uneconomic" and discontinued.
Although
dead salmon and their wastes can be safely disposed of with various
filtration and treatment systems to protect marine ecosystems, the
salmon farming industry has resisted all such proposals in the interest
of keeping costs low to offer the cheapest product possible. The savings
to consumers, however, means a far heavier price must be paid by wild
salmon, the shellfish industry, and traditional commercial fishing
livelihoods. More to the point, no one yet knows the true cost of cheap
farmed salmon to human health.
- S. J. Cripps and L. A. Kelly, “Reductions in wastes from aquaculture,” In D. J. Baird et al. (eds.), Aquaculture and water resource management, Blackwell Science, Oxford, 1996. See also J. R. Henderson et al., “The lipid composition of sealoch sediments underlying salmon cages,” Aquaculture, 158:69 (1997), pp. 83-89.
- M. MacGarvin, “Scotland’s secret? Aquaculture, nutrient pollution, eutrophication and toxic algal blooms,” WWF Scotland, Aberfeldy (2000), wwf.org.uk/fileLibrary/pdf/secret.pdf>.
- R. W. Hardy, “Urban legends and fish nutrition,” Aquaculture Magazine, Nov/Dec (2000), issues00/00articles/ND2000Urban.pdf>.
- Scottish Executive, “Eutrophication assessment of aquaculture hotspots in Scottish coastal waters,” Paper presented to OSPAR by the Scottish Executive, May 2003, .
- D. J. Wildish et al., “Acoustic detection of organic enrichment in sediments at a salmon farm is confirmed by independent groundtruthing methods,” Marine Ecology Progress Series 267 (2004), pp. 99-105, .
- K. Haya, “Environmental impacts of chemical wastes produced by the salmon aquaculture industry,” In B. T. Hargrave [ed.]. Environmental Studies for Sustainable Aquaculture 2002 Workshop Report, (Canadian Technical Report), Canadian Bulletin of Fisheries and Aquatic Sciences, 2411 (2002), .
- P. W. Balls, “Tributyltin (TBT) in the waters of a Scottish sea loch arising from the use of antifoulant treatment netted by salmon farms,” Aquaculture, 86 (1987), pp. 227–237.
- C. D. Miranda et al., “Diversity of tetracycline resistance genes in bacteria from Chilean salmon farms,” Antimicrobial Agents and Chemotherapy 47 (2003), pp. 883–888, .
- “Fears raised by salmon dump,” The Sunday Times, July 17, 2004, posted on “Aquaculture Corner,” of the Mangrove Action Project, org/map/ltfrn_159.htm>.
- G3 Consulting, Salmon Aquaculture Waste Management Review & Update, Report prepared for British Colum
