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Devastating Report Details Aquaculture Dilemmas

Greenpeace details the fundamental problems and contradictions associated with fish farming, and makes key recommendations

by Craig Weatherby

The world faces hard choices when it comes to using fish as food.

For many of the world's poor people, fish rank high among cheap protein sources.

And in affluent nations, where calories are abundant but “junky,” research results continue to ratify the importance of raising intake of omega-3 and vitamin D: two nutrients in which fish are uniquely rich.

Green leafy plants (e.g., spinach, kale, collards, chard, purslane), walnuts, and animals raised on grass provide small amounts of the short-chain omega-3 called ALA, which the body converts, very inefficiently, to the long-chain omega-3s it actually uses (EPA and DHA).

But green vegetables are cost-inefficient sources of omega-3s. And while canola and soy oils are cheap and contain about seven percent omega-3 ALA, they contain four to seven times as much omega-6 fatty acids, which compete with omega-3s for absorption into cell membranes.

With a few exceptionsnotably, Alaskan Salmon, North Pacific Tuna, and the other certified-sustainable wild species we sellwild fish stocks are in decline.

And that situation's only getting worse, as The New York Times reported recently with regard to rapid depletion of West Africa's subsistence fisheries, solely to feed affluent European's craving for seafood (See “Europe Takes Africa's Fish, and Migrants Follow” and “Europe's Appetite for Seafood Propels Illegal Trade”).

Accordingly, fish and shellfish farming (aquaculture) is an increasingly important source of seafood, providing an estimated 43 percent of all the seafood consumed worldwide (FAO 2007).

While we support sustainable aquaculture, a new report from Greenpeace a sobering read. The study, released late last month, provides a comprehensive overview of the problems associated with modern fish and shellfish farming, and offers some solutions.

We've excerpted some of the highlights below. You can read the full report, with references, here.

For ease of reading we've removed citations from the text, underlined key points, and inserted some clarifying comments in brackets [like this].

Excerpts from “Challenging the Aquaculture Industry on Sustainability”

By Michelle Allsopp, Paul Johnston, and David Santillo at Greenpeace Research Laboratories, University of Exeter, UK.

Farming CarnivoresA Net Loss of Protein

The aquaculture industry has consistently promoted the idea that its activities are key to assuring future sustainable world fish supplies and will relieve pressures on over-exploited marine resources. In fact, in the case of carnivorous fish and shrimp the input of wild caught fish exceeds the output of farmed fish by a considerable margin, since conversion efficiencies are not high.

For example, each kilogram of salmon, other marine finfish or shrimp produced may use 2.5–5 kg of wild fish as feed. For tuna ranching, the ratio of wild fish needed as feed to the amount of tuna fish produced is even higher20 kg fish feed to 1 kg farmed fish.

Thus, farming of carnivorous species results in a net loss rather than a net gain of fish protein. Instead of alleviating pressure on wild fish stocks, therefore, aquaculture of carnivorous species increases pressure on wild stocks of fish, albeit of different species. With further intensification of aquaculture and expansion of marine finfish aquaculture, it is likely that demand for fishmeal and fish oil will even outstrip the current unsustainable supply.

Demands for Fishmeal and Fish Oil in Aquaculture

The quantity of fishmeal and fish oil used by the aquaculture industry has increased over the years as aquaculture has expanded and intensified. In 2003, the industry used 53% of the total world's fishmeal production and 86% of the world's fish oil production.

The increased demand for fishmeal and fish oil by aquaculture has been met by diverting these products away from their use as feed for agricultural animals, in itself a controversial issue. [This shift means that eggs, meats and poultry are lower in omega-3s than they could be.] Currently, agricultural use of fishmeal and fish oil is increasingly restricted to starter and breeder diets for poultry and pigs.

Fish oil previously used in the manufacture of hard margarines and bakery products has now been largely diverted to aquacultural use.

Although a trend has emerged in recent years of replacing fishmeal with plant-based proteins in aquaculture feeds, the fraction of fishmeal/oil used for diets of carnivorous species remains high.

Moreover, this trend has not been fast enough to offset the growing use of fishmeal, caused simply by an increase in the overall number of farmed carnivorous fish produced. For example, the quantity of wild fish required as feed to produce one unit of farmed salmon reduced by 25% between 1997 and 2001, but the total production of farmed salmon grew by 60%, eclipsing much of the improvement in conversion efficiencies.

Use of Fishmeal/Fish Oil/Bycatch in Aquaculture Feeds

The use of fishmeal and fish oil derived from marine species of fish for aquaculture also has implications for human food security. For example, in Southeast Asia and Africa, small pelagic (open water) fish such as those targeted by industrial fisheries are important in the human diet.

Demand for such fish is likely to grow as populations increase, bringing them under pressure both from aquaculture and direct consumption. In addition, low value fish (inappropriately termed “trash fish”) caught as by-catch and used for fishmeal production are actually an important food source for poorer people in developing countries. Use of “trash fish” in aquaculture inflates prices such that the rural poor can no longer afford to buy it.

With these factors in mind, the UN Food and Agricultural Organization (FAO) has recommended that governments of major aquaculture producing countries prohibit the use of “trash fish” as feed for the culture of high value fish.

Moving Towards More Sustainable Feeds

The aquaculture industry is highly dependent upon wild caught fish to manufacture feed for cultured species. This is widely recognized as an intensive and generally unsustainable use of a finite resource. In turn, the industry has recognized the need to evaluate and use more plant-based feed materials and reduce dependence on fishmeal and fish oil.

Plants are already used in aquaculture feeds. Those that are used and/or show particular promise for the future include soybean, barley, canola, corn, cottonseed and pea/lupin. It is important to note that if plant-based feeds are used in aquaculture, to be sustainable they must be sourced from agriculture that is sustainable.

For some herbivorous and omnivorous fish, it has been possible to replace completely any fishmeal in the diet with plant-based feedstuffs without impacts on fish growth and yield.

[However, giving farmed fish feed high in plant matter raises their omega-6 content and reduces their omega-3 content, which exacerbates the unhealthfully high omega-6/omega-3 ratio in American's diets.]

Feeding of carnivorous species seems to be more problematic. Fishmeal and fish oil can be reduced by at least 50% in the diet, but complete substitution for plant ingredients has not yet been possible for commercial production.

Problems [of shifting to plant-based fish-feed] include the presence of certain compounds in plants that are not favorable to fish, known as anti-nutritional factors, and the lack of certain essential (omega-3) fatty acids. Oily fish is considered to be an important source of omega-3 fatty acids in human nutrition, but feeding fish with plant oil-based diets alone reduces the amount in their flesh. Recent research, however, has found that the fish oil input could be reduced by feeding fish with plant oils but switching to fish oils in the period just prior to slaughter. Recent research on marine shrimp suggests that it may be possible to replace fishmeal in the diet largely with plant-based ingredients, although further study is needed.

Moving Towards Sustainable Aquaculture Systems

In order for aquaculture operations to move towards sustainable production, the industry needs to recognize and address the full spectrum of environmental and societal impacts caused by its operations. Essentially, this means that it will no longer be acceptable for the industry to place burdens of production, (such as the disposal of waste) onto the wider environment.

In turn, this implies moving towards closed production systems. For example, in order to prevent nutrient pollution, ways can be found to use nutrients present in waste products beneficially. Examples include integrated multi-trophic aquaculture (IMTA), aquaponics and integrated rice-fish culture.

In aquaponics systems, effluents from fish farming are used as a nutrient source for growing vegetables, herbs and/or flowers. One existing commercially viable aquaponics system involves the cultivation of tilapia in land-based tanks from which the waste water is used to grow vegetables (without soil) in greenhouses.

A company in the Netherlands called ‘Happy Shrimp' partially use waste from their farms to grow vegetables. The shrimp are fed on algae and bacteria as well as on aquaculture feed containing a high proportion of plant protein. The shrimp are cultivated in greenhouses and no shrimp juveniles are extracted from the wild.

In integrated rice–fish culture, fish are cultivated alongside rice, which optimizes use of both land and water. The nitrogen-rich fish excretory products fertilize the rice, and the fish also control weeds and pests by consuming them as food. Much of the fish nutrition is derived naturally in this way. Major constraints to widespread use of such methods include the fact that many farmers are not educated in the required skills67. This could be overcome if policy makers gave active support to this practice. Integrated rice–fish culture is crucial for local food security rather than for supplying export markets.

The growth of aquaculture has led to a multiplicity of concerns attached to environmental impacts, social impacts, food safety, animal health and welfare and economic/financial issues. All of these factors influence the sustainability of a given aquaculture system.

Presently, there are a growing number of certification schemes which seek to reassure buyers, retailers and consumers about various of these concerns. Currently existing certification schemes, however, do not cover all of these issues and can sometimes present a confusing and conflicting picture to retailers and consumers. A recent analysis of 18 aquaculture certification schemes by the World Wildlife Fund (WWF) showed that they generally had major shortcomings in terms of the way in which they considered environmental standards and social issues.

Salmon Farms: Negative Impacts on People and on the Environment

Nutrient Pollution

Organic wastes from fish or crustacean farming include uneaten food, body wastes and dead fish. In salmon farming, these wastes enter the aquatic environment in the vicinity of the cages. In extreme cases the large numbers of fish present in the cages can generate sufficient waste to cause oxygen levels in the water to fall, resulting in the suffocation of both wild and farmed fish.

More usually, the impacts of intensive salmon culture are seen in a marked reduction in biodiversity around the cages. For example, a study in Scotland found a reduction in biodiversity on the seabed up to 200 meters away from salmon cages. In Chile, biodiversity close to eight salmon farms was reduced by at least 50%.

Wastes can also act as plant nutrients and, in areas where water circulation is restricted, these may also lead to the rapid growth of certain species of phytoplankton (microscopic algae) and filamentous algae. Some of the algal blooms which can result are very harmful: they can cause the death of a range of marine animals and also cause shellfish poisoning in humans.

Threat to Wild Fish from escaped Farmed Salmon

Farmed Atlantic salmon have a lower genetic variability than wild Atlantic salmon. Hence, if they interbreed with wild salmon, the offspring may be less fit than wild salmon and genetic variability that is important for adaptability in the wild may be lost. It was originally thought that escaped salmon would be less able to cope with conditions encountered in the wild and would be unable to survive, thereby not posing a threat to the genetic diversity of wild populations.

In reality, the sheer numbers that have escaped (an estimated 3 million per year) mean that they are now breeding with wild salmon in Norway, Ireland, the United Kingdom and North America. Because they produce offspring less able to survive in the wild, this means that already vulnerable populations could be driven towards extinction.

In Norway, farmed salmon have been estimated to comprise 11–35% of the population of spawning salmon; for some populations this may rise to more than 80%. Continuing escapes may mean that the original genetic profile of the population will not re-assert itself.

In addition to threats to wild Atlantic salmon caused by escapees in their native regions, farmed Atlantic salmon that have been introduced to Pacific streams pose a threat to other native fish populations, such as steelhead in North America and galaxiid fishes in South America, because they compete for food and habitat.

Diseases and Parasites

Diseases and parasites can be particularly problematic in fish farming where stocking densities are high. Wild populations of fish passing near to farms may also be affected. One notable example is that of parasitic sea lice which feed on salmon skin, mucous and blood and which can even cause the death of the fish. There is evidence that wild salmon populations have been affected by lice spread from farms in British Columbia and Norway.

Recent research in British Columbia suggests that sea lice infestation resulting from farms will cause the local pink salmon populations to fall by 99% within their next four generations. If outbreaks continue unchecked, extinction is almost certain.

[Note: See our accompanying article on Alexandra Mortonone of the co-authors of this studyand her Raincoast Research Foundation.]

Chilean Salmon Farms: Human Rights Issues

In southern Chile the salmon farming industry has grown rapidly since the late 1980s to serve export markets in western nations. In 2005, nearly 40% of the world's farmed salmon was supplied from Chilean producers and processors.

This burgeoning industry has an appalling safety record. Poor or nonexistent safety conditions have been widely reported on Chilean farms and in processing plants. Over the past three years there have been more than 50 accidental deaths, mostly of divers. By contrast, no deaths have been reported in the Norwegian salmon industry, the world's largest producer of salmon.

Reports from Chile also tell of low wages (around the national poverty line), long working hours, lack of respect for maternity rights and persistent sexual harassment of women.


Any aquaculture that takes place needs to be sustainable and fair. For aquaculture systems to be sustainable, they must not lead to natural systems being subject to degradation caused by:

  1. An increase in concentrations of naturally occurring substances,
  2. An increase in concentrations of substances, produced by society, such as persistent chemicals and carbon dioxide and physical disturbance.

In addition people should not be subject to conditions that systematically undermine their capacity to meet their basic needs for food, water and shelter.

In practical terms, these four conditions can be translated into the following recommendations:

Use of Fishmeal, Fish oil and “Trash Fish”: To reduce the pressure on stocks caught for fishmeal and fish oil, there needs to be a continued move towards sustainably produced plant-based feeds.

Cultivating fish that are lower down the food chain (herbivores and omnivores rather than top predators [like Salmon]) that can be fed on plant-based diets is key to achieving sustainable aquaculture practices. Industry must expand its research and development on herbivorous and omnivorous fish which have strong market potential and suitability for farming.

Greenpeace considers the culture of species that require fishmeal or fish oil-based feeds derived from unsustainable fisheries and/or which yield conversion ratios of greater than one (i.e. represent a net loss in fish protein yield) as unsustainable. Plant-based feeds should originate from sustainable agriculture, and sources of omega 3 should be algal derivatives, grape seed oils, etc.

Escapes of Farmed Fish to the Wild: To overcome these problems it has been suggested that enclosed bag nets/closed wall sea pens should be used to prevent fish from escaping, or that land-based tanks should be used. Ultimately, land-based tanks are the only option if the goal is to eliminate any risk of escapes which might otherwise occur as a result of hurricanes or other extreme weather events at sea. It is crucial to use native rather than exotic species.

Greenpeace recommends that only species which are native should be cultivated in open water systems, and then only in bag nets, closed wall sea pens or equivalent closed systems. Cultivation of nonnative species should be restricted to land-based tanks.

Protection of Local Habitat: Some aquaculture practices have had serious negative impacts on local habitat. Aquaculture practices must be set up in a way that provides for the protection of coastal ecosystems and local habitats. In addition, no new aquaculture practices should be permitted in areas that are to be designated as marine reserves and any existing aquaculture operations within such areas should be phased out.

Greenpeace considers aquaculture which causes negative effects to local wildlife (plants as well as animals) or represents a risk to local wild populations as unsustainable.

Use of Wild Juveniles: The use of wild-caught juveniles to supply aquaculture practices, particularly some shrimp aquaculture, is destructive to marine ecosystems.

Greenpeace considers aquaculture which relies on wild-caught juveniles as unsustainable.

Transgenic Fish: The physical containment of genetically engineered fish cannot be guaranteed under commercial conditions and any escapes into the environment could have devastating effects on wild fish populations and biodiversity71.

Greenpeace demands that genetic engineering of fish for commercial purposes should be prohibited.

Diseases: Greenpeace recommends cultivation at stocking densities that minimize the risk of disease outbreaks and transmission and, therefore, minimize requirements for therapeutic treatments.

Resources: Greenpeace considers aquaculture that depletes local resources, for example, drinking water supplies and mangrove forests, as unsustainable.

Human Health: Greenpeace considers aquaculture that threatens human health as unfair and unsustainable.

Human Rights: Greenpeace considers aquaculture that does not support the long-term economic and social well-being of local communities as unfair and unsustainable.


  • Greenpeace. Challenging the Aquaculture Industry on Sustainability. Accessed online February 5, 2008 at
  • FAO (2007). The state of world fisheries and aquaculture 2006. FAO Fisheries and Aquaculture Department. Food and Agricultural Organization of the United Nations, Rome, Italy. 162 pp.


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