Three billion people around the globe regularly eat what the French call, in something of a naïve misnomer, “fruits of the sea.” As output from the planet’s wild fisheries drops like a barometer before a storm, aquaculture—or fish farming—is increasingly taking up the slack. That makes it the planet’s fastest growing food production system, and today, half the fish Americans eat is raised in tanks, cages, and other confinement systems.[i] Many believe aquaculture is a sustainable, cost-effective way to feed the planet, especially as the production of meat and dairy is increasingly seen as unsustainable at the levels the world demands. Is fish farming the way of the future?
Recall the Polyface Farm model for land animals. The technique of ecological rotation for farming livestock is one of the most sustainable ways (even if not completely sustainable) to feed animals, manage waste, and avoid degrading the land. In a similar vein, innovative fish farming methods surround the target species with a mini-ecosystem to promote natural waste management. Salmon, for example, might be raised next to shellfish, which filter solid waste, and seaweed, which processes nitrogen. One such efficient system is called Integrated Multi-Trophic Aquaculture (IMTA), and it’s in use today at several aquatic farms in Canada’s Bay of Fundy. IMTA isn’t perfect, but it does help address one of the biggest concerns in fish farming—the effects of fish waste on surrounding ecosystems.
But waste is only one of several issues in aquaculture sustainability. In fact, the most eco-friendly way to raise fish is to grow them in land-based tanks or ponds where waste is completely contained, disease is minimal, and escapes are impossible. However, unlike open-water systems, land-based systems require costly processes to remove waste and to maintain water’s salinity, temperature, and oxygen content.
Fish-farming scientists at the University of Maryland have sought to address the ecological limitations of fish farming. Led by Yonathan Zohar, chair of the university’s Department of Marine Biotechnology, the group has developed a fully self-contained, land-based aquaculture system. The Maryland system uses bacteria to filter nitrogen from the water and microbes to convert waste to methane for use as a biofuel. It’s about as eco-friendly as fish farming can be. However, it’s not ready for production—and may never be. Not surprisingly, this system is limited by its high operating costs and the huge amounts of energy needed to run it.
Aquaculture methods like IMTA and the Maryland system are promising. But just as Polyface Farm is well-intentioned but ultimately unsustainable, these and other innovative fish farming methods also fall short. For starters, land-based systems, even those that don’t take the costly extra step of recycling water and waste, are expensive. In a cage or pen system, by contrast, because the permeable container sits in open water, operators spend nothing to dispose of waste or to provide a constant supply of clean, oxygenated water. This fundamental difference allows cage and pen systems to operate much more cheaply than land-based systems. It also explains why cage aquaculture is the predominant method of fish farming throughout the world. [ii]
IMTA, for its part, may be an effective way to protect ecosystems from fish waste. However, IMTA doesn’t address a number of other ecological concerns associated with open-water fish farming discussed below. And even if they did, IMTA and similar systems are in use at only a handful of fish farms. The reality is that fish farm operators, like any business owners, look to the bottom line—and we know that price tags are closely watched in the world of meatonomics. That’s why inexpensive cage-based systems are the standard. And as experience shows with largely futile efforts to reform land-based animal production methods, in an industry characterized by regulatory capture and heavy influence over lawmaking, it’s likely to stay that way. Hence, in evaluating fish farming, while the experiments of innovators on the fringe are interesting, the relevant point of inquiry is the system as it exists today and is likely to persist in the future. And here’s where the water gets a bit murky. Considering the many documented environmental impacts of aquaculture as practiced today in North America and around the world, the claim that it’s sustainable emerges as something of a fish story.
Sustainability Issues in Fish Farming
Fish farms are the factory farms of the sea. And just like CAFOs, aquaculture relies on hyper-confinement to raise the largest number of animals in the smallest possible area. With two-thirds of the planet covered in water, it might not be necessary to stock fish as densely as battery hens. But necessary or not, that’s how it’s done. Foot-long trout, for example, are raised in densities as tight as twenty-seven to a bathtub-sized space.[iii] And just as such tight densities cause problems in factory farms, they cause a variety of issues in fish farms.
Fish are susceptible to parasites. While these vermin can only achieve infestation at high density levels, a typical fish farm provides the Goldilocks-like stocking levels they need.[iv] Atlantic salmon, the most common cage-reared fish, are particularly prone to sea lice. A parasitic crustacean measuring an inch or longer and resembling a miniature horseshoe crab, these dogged little creatures eat the blood, mucous, and tissue of living salmon. Because sea lice can only survive in saltwater, they typically drop off in the wild as their hosts migrate into fresh water. In saltwater fish farms, however, lice remain attached until removed by chemicals or, in some cases, gobbled by lice-eating cleaner fish.
A female sea louse lays up to twenty-two thousand eggs during her seven-month lifespan.[v] On tightly packed fish farms, newly hatched juvenile lice have little trouble finding a host to chew on. Picture, if you will, the huge numbers of concentrated salmon and egg-laying sea lice in a typical fish farm environment. With more than five hundred thousand salmon in an average farm, if just one in ten fish hosts just one female louse, and each louse lays just half her capacity, that’s a localized plague of more than 500 million baby sea lice. Besides hurting farmed fish, these infestations also harm the surrounding ecosystem and its inhabitants. Like a swarm of tiny locusts, the hungry parasites explode into their surroundings and snack on any wild salmon in the vicinity.
Not surprisingly, sea lice from salmon farms are killing wild salmon populations.[vi] On Canada’s Pacific coast, for example, sea lice infestations are responsible for mass kill-offs of pink salmon that have destroyed 80 percent of the fish in some local populations.[vii] But the damage doesn’t end there, because eagles, bears, orcas, and other predators depend on salmon for their existence. Drops in wild salmon numbers cause these species to decline as well.[viii]
Some farmers respond to lice by dosing the water with concentrated chemicals that kill the tiny creatures. Not surprisingly, adding toxins to the ocean harms the local ecosystem.[ix] One study, for example, found that cypermethrin (used to kill lice on salmon) kills a variety of nontarget marine invertebrates, travels up to half a mile, and persists in the water for hours.[x]
But even more threatening to local ecosystems than sea lice and the chemicals that kill them are the massive quantities of waste generated by most fish farms. Consider aquaculture’s effect in Scotland. In 2000, Scotland’s fish farm industry created as much waste-based nitrogen as did two-thirds of the country’s human population of 5 million—plus almost double the phosphorus that the human population generated.[xi] Fish waste typically falls as sediment to the seabed in sufficient quantities to overwhelm and kill underlying marine life in the immediate vicinity and for some distance beyond. It also promotes algal growth, or the ironically named process of eutrophication (literally, “providing nourishment”), which reduces water’s oxygen content and makes it less capable of supporting life. In 2008, the Israeli Ministry of Environmental Protection shut down two fish farms in the Red Sea that produced 2,000 tons of fish annually, because research showed that eutrophication from the fish farms was damaging the region’s coral reefs.
Aquaculture also results in regular escapes by farmed fish into the world’s oceans. In the North Atlantic region alone, up to 2 million runaway salmon escape into the wild each year.[xii] The result is that at least 20 percent of supposedly wild salmon caught in the North Atlantic are of farmed origin.[xiii] Escaped fish breed with wild fish and compromise the gene pool, harming the wild population. Embryonic hybrid salmon, for example, are far less viable than their wild counterparts, and adult hybrid salmon routinely die earlier than their purebred relatives.[xiv] Like hitting a fighter when he’s already down, this gene-pool degradation causes further declines in wild fish stocks that have already been pounded by overfishing.
Excerpt from Meatonomics: The Bizarre Economics of Meat and Dairy - see the VLV! interview here.
David Robinson Simon is a lawyer, animal advocate, and proponent of sustainable consumption. He works as general counsel for a healthcare company and serves on the board of the APRL Fund, a non-profit dedicated to protecting animals. David received his B.A. from U.C. Berkeley and his J.D. from the University of Southern California.
[i] National Oceanic and Atmospheric Administration, “Fishwatch: U.S. Seafood Facts,” accessed October 1, 2012, http://www.fishwatch.gov.
[iii] Philip Lymberly, “In Too Deep: The Welfare of Intensively Farmed Fish,” Compassion in World Farming Trust (2002), accessed October 1, 2012, at http://www.ciwf.org.uk.
[v] A. Mustafa, G.A. Conboy, and J. F. Burka, “Life-Span and Reproductive Capacity of Sea Lice, Lepeophtheirus salmonis, under Laboratory Conditions,” Aquaculture Association of Canada Special Publication 4 (2000): 113–14.
[x] W. Ernst et al., “Dispersion and Toxicity to Non-Target Aquatic Organisms of Pesticides Used to Treat Sea Lice on Salmon in Net Pen Enclosures,” Marine Pollution Bulletin 42, no. 6 (2001): 433–44.
[xi] M. MacGarvin, “Scotland’s Secret: Aquaculture, Nutrient Pollution, Eutrophication and Toxic Blooms,” WWF Scotland (2000), accessed October 1, 2012, http://assets.wwf.org.uk.
[xiii] L. P. Hansen, J. A. Jacobsen, and R. A. Lund, “The Incidence of Escaped Farmed Atlantic Salmon, Salmo salar L., in the Faroese Fishery and Estimates of Catches of Wild Salmon,” ICES Journal of Marine Science 56 (1999): 200–6.
- Published: 25 February 2014
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