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FARMED FISH FOLLIES: ACT II: Marine aquaculture choices

5 years ago, Written by , Posted in Articles, Media re-posts

By Boyce Thorne Miller, NAMA’s Science Coordinator

Source: who fishes matters

ACT II: Marine aquaculture choices

In a minor adjustment of this 3-part blog, I have decided to make this one about the choices we have as consumers and stewards of the marine ecosystem relative to farmed seafood. It gives folks purchasing guidelines with simplified justifications. This will be followed by the final blog, which will be a more in-depth review of some of the history that lies behind the guidelines – for braver souls who want more information.


Consumer Guidelines for Marine Farmed Fish

So here is the first general rule of purchasing farmed seafood, especially those frozen packages in your supermarkets and big box stores:  Don’t feel self-righteous about it. Don’t think you are doing anything to save wild fish and shellfish, and don’t think your purchase is contributing to the wellbeing of hungry people around the world or their access to seafood. There may be a few cases in which this rule does not apply, but it is generally a good guideline when you have no reliable information to the contrary.

Now for more specific guidelines to follow when you purchase farmed seafood, which gnerally falls into three large categories—finfish, shellfish, and seaweed. Since seaweed does not have much of a market in the US, I’ll leave that for the historical perspective in the next blog. The following recommendations are for farmed fish and shellfish.


Finfish guidelines:

Tilapia and other farmed herbivores. Fish that feed low on the food chain are generally a better choice because farms should not have to use wild-caught fish to supplement their feed. However, just like industrial agriculture, industrial fish farming often adds fishmeal to the feed of herbivorous animals. Tilapia is no exception. And it’s almost impossible for you, as a consumer, to know whether the Tilapia you are considering has been fed wild fish. Demanding regulations for informative labeling would be a good start.

Salmon and other carnivorous fish.   At the heart of the marine fish-farming industry in the developed world is the intensive, large-scale cultivation of predatory fish—most commonly salmon, but other fish are rapidly coming on line.   Salmon farming is highly profitable but not environmentally sustainable, and it is unlikely that it will ever be so since it violates so many principles of good animal husbandry and efficient human food production:  the animal being grown is a top predator so more protein goes in than is produced; densities of animals are so great that they are stressed and disease is rampant; they are grown in systems that expose wild fish and ecosystems to the disease and wastes flowing from the fish farms; the waste is allowed to flow out like raw sewage and may drift in concentrated masses for long distances; fish escape from the farms by the thousands; and sea mammal predators attracted to the farms are often killed.

So in this case, we can offer a simple guideline to fish consumers considering these farmed carnivorous marine fish. Just Say No!  And when asked, here’s why:

 *      Would you farm and eat tigers? Most marine fish that are farmed are top predators that must be fed meat, in particular other fish. It takes about 5 pounds of feed fish to produce a pound of salmon. And that feed fish is wild caught fish that should be feeding the wild fish of our ocean ecosytems.

 *      Farmed fish make wild fish sick. Fish farms harbor diseases and parasites that, experience has proven, are passed to nearby wild populations of fish. Even when effective drug treatments are applied so that the farmed fish are largely uninfected, infected wild fish are increasingly turning up. Salmon is the poster child for this disaster, and sea lice infections the most graphic example. So when salmon farms are dense, wild populations of salmondecline rather that prosper. So much for the argument that aquaculture saves wild fish populations.

 *     Open water fish farms discharge raw sewage. Fish farms in natural waters have virtually no constraints on the effluent of waste—fish excrement. When developed on an industrial scale, with numerous pens in close proximity in coastal areas, waste production is equivalent to a city but there are no requirements for sewage treatment. Recent research shows that the effluent is not immediately diluted because it is flowing into water. Instead the mechanics and stratification of the water cause the waste to remain concentrated for long distances, sometimes encountering coastlines before it disperses

 *   Penned fish often escape in huge numbers. When a fish pen is breached, thousands or tens of thousands of fish flee into surrounding waters, where they become part of the wild fish community. Some say, “So what? They just provide more fish for the capture fisheries to catch!”   But it’s not that simple. Escaped fish may spread disease; they may eat healthier wild fish; they may interbreed with wild individuals of their own species; they may compete with other wild predatory fish for food and with other anadromous fish (saltwater fish that migrate and breed in fresh-water) for breeding habitat.

What’s wrong with interbreeding and thereby adding to the populations of their wild sisters and brothers?  Wild fish populations have genetic characteristics that have been honed through selection for their survival advantage over long periods of evolution. Farmed fish are bred and raised under conditions that do not demand the same rigor for survival in the wild. Consequently repeated interbreeding over time can cause the wild populations to weaken and become more vulnerable to harsh environmental conditions.


While large escapes are most infamous and well documented, the constant trickle of single fish escaping–through small breaks or commonly during transfer of fish into or out of pens–can add up to thousands that have the same long term effects on wild populations.

Escapes from salmon farms in the Pacific have an additional impact, caused by adding a new species (Atlantic salmon) into the wild to compete with native Pacific salmon species.

Several other fish species are grown in factory farms in Hawaii and commonly appear in supermarkets and other fish counters. The “just say no” rule still applies!

Genetically engineered fish.  With farming comes the ever-present scepter of genetic engineering, andfish are no exception. A Massachusetts company has applied for FDA approval to market genetically engineered salmon in the US. So far their prototype production is limited to Canada (brood stock) and Panama (adult fish production). The scales would increase with all the same threats of usual salmon aquaculture but the added threat of genetic engineering in the food supply and escaping into the wild. Don’t let the FDA approve the marketing of this fish or any other genetically altered fish!  And demand labeling if any genetically engineered food products are permitted on the market.

A word of caution to nutrition enthusiasts. Farmed salmon is marketed primarily to health-conscious, prosperous people who have been advised by the medical profession to eat plenty of fish. Salmon, because of its ubiquitous availability as farmed fish in North America and Europe, often spills out as a suggested choice. And no distinction is made between wild and farmed. Yet if high amounts of omegas and high Omega 3/6 ratios are what is desired by privileged societies and classes who can afford to think about long, healthy lives, we should choose wild over farmed—even better, herring and mackerel over salmon. And omega supplements should be made from algae instead of fish (which get theirs from algae). With these changes fishmeal and fish oil would loose their value and forage fish would be left in the sea to serve marine food chains and be fished in much smaller quantities for local fresh fish markets.


Shellfish Guidelines
Farmed shrimp. As you contemplate shrimp in your supermarkets and on restaurant menus, remember these come primarily from large-scale export shrimp aquaculture industries in tropical, often less-developed, countries with poor regulations.  Though a few sustainable farms might be found in the US, almost all the shrimp you find in markets will come from abroad. Wild-caught options appear occasionally during shrimping seasons in Maine and the Gulf of Mexico, and that can be a better bet, especially locally. But the safe and simplest answer to farmed shrimp, is once again, to “just say no.”  Here’s why:

*  Shrimp farming in coastal areas that once supported rich mangrove forests is notorious for destroying coastal ecosystems.

*    Shrimp farms are associated with heavy use of antibiotics.

*    Shrimp farming deprives local people of their access to coastal areas and their resources and the farms are often known for mistreatment of workers.

*    Shrimp farming profits private companies, sometimes foreign, and does not benefit local peopleand their need for food.

 *    Intensive, destructive, shrimp aquaculture feeds the gluttonous demand for shrimp in international food and restaurant chains and luxury food markets of the world. It is not about feeding the hungry or those who wish to eat compatibly with natural ecosystems.


When it comes to molluscan shellfish, there are good aquaculture choices available, so you need to be more aware of the dos and don’ts. Look for shellfish farming done on scales and in locales that are not only good for the seafood market, but also for the ecosystems in which they sit. But even though shellfish farmers would all prefer that you allow them to rest on the laurels of good shellfish farming and consider it all benign, it’s important to know that some shellfish farming practices are harmful to ecosystems.

Typical shellfish that are farmed include a variety of oysters, clams, mussels, scallops, and abalone. For examples of shellfish farming at it’s worst, we need look no further that our State of Washington, where economic power and politics rule shellfish farm development. But Canadian and European examples abound as well. Because shellfish farming almost always occurs in wild ecosystems near shore, the problems may be significant and very obvious, although they are avoidable with careful regulation and management.

The most reliable rule for these farmed shellfish is “know your farmer and farming technologies.”  If you can’t get the information you need regarding mass marketed farmed shellfish it’s best to buy from local farmers whose practices you can evaluate. You’re likely to get a better quality product that way, too.


These are the potential problems you need to watch out for:

*  The scale can be too large for the ecosystem. In the Pacific Northwest coastal and estuary aquaculture, this is a serious problem, but as the demand for aquaculture products increases, other locations around the country’s coastlines may come under siege. The development of aquaculture is often disorganized and poorly regulated, until after damage has been done. Offshore open ocean shellfish farms, common along the Atlantic coast of Europe and northeastern Canada, are even more massive and associated with chemical and organic pollution and other impacts inherent to monoculture factory farms.

*    Water quality requirements may be counter productive, preventing farms from being located in best sites. While it is essential that seafood be safe for the consumer, shellfish farms are often most useful when they can also serve to clean up the water of excessive phytoplankton blooms, which are not the associated with the highest water quality but may not always indicate unhealthy conditions.  In some places, potential contamination problems can be averted by placing shellfish into clean-water lots for final purging; or shellfish in highly contaminated locales may simply be used to clean the water and not be marketed.  That approach can create new areas suitable for shellfish farming for food.

 *  Bottom habitats may be destroyed. Most shellfish farms have a footprint on the seafloor, and in some cases the impacts may seriously degrade healthy seafloor ecosystems. But, if properly sited where the bottom is not naturally very productive, the impact may be very small.

 *   Water quality in some cases may deteriorate, when shellfish farms are so massive that the organic debris from them actually fouls the water or the bottom beneath the shellfish farms.

  The farm consumption of the natural food supply may compete with wild plankton feeders in the ecosystem. Some states avoid this by requiring that farms be located in areas that do not support significant wild shellfish populations.

 *  The siting can interfere with wild shell-fisheries or citizen’s access to the waterfront and to natural marine resources. There is greatest potential for this when aquaculture is located in intertidal areas; for example geoduck farming in Washington.

*     Introduction of non-native and invasive species is often associated with aquaculture.  It may be the farmed species itself or other species that hitchhike on the seed stocks or proliferate on the farms. A prime example is the Pacific oyster, which has replaced native species round the world, including in Washington. And industrial mussel farms off Prince Edward Island are awash with massive growths of invasive tunicates.

 *   Use of pesticides is common in large-scale aquaculture, where competitors or foulers in the farm beds or rafts are killed with chemicals. Examples include pesticide applications to kill native ghost shrimp in the sediments of big bottom-culture oyster farms in Washington State, and antifouling treatments on the P.E.I. mussel farms. Mussels themselves are often considered pests on salmon farms, where chemicals may be used to get rid of them.

*   Important aesthetic values of shorelines can be destroyed. Do you value the influence of natural seascapes on our psyches and our arts?


For some time US aquaculturists have said that their important industry is severely hampered by rich coastal dwellers who have paid big bucks for a view of the sea. Well I don’t know about you, but I am not rich, and I cannot afford ocean-front property, but I most certainly value the access I have to sit on the shore and be soothed or inspired by the sea and shore-scapes. Seafood farms of all kinds need to be sited and designed to minimize their impacts on that. As with working waterfronts for commercial fisheries, there is a place for everything, but some aquaculture developers would suggest there is no place for us. And the federal government, by promoting industrial aquaculture far offshore, would like to put the farms and their inherent problems out of sight and out of mind.

There are many shellfish farms and few fish farms that do not fall into the destructive patterns described in the points above. Always be aware of the potential problems and choose which farmers to support – through your buying choices and your political power to influence government policy. Nearshore marine farming is regulated by individual states but often promoted by federal funding and national policy, so you need to apply pressure at both levels to make sure your coastal state is ready for expanding aquaculture development with solid, ecologically defensible options, regulations and guidelines.



  • Jan Stehlík

    Intersting information. The aquaculture indeed could have some downsides when done recklessly, but eating wild fish caught with dragged nets is even worse option.
    So what are you giong to do? Are you a vegan?

    If not, then aquaculture is the best choice for suplying you the meat you want. I don’t see any other option.