Aquaculture: Fishing for answers


Photo credit: Angela Y. Martin

A few weeks ago I was a guest at the Canadian Aquaculture Industry Alliance‘s Farmed Seafood Extravaganza held at Starfish Restaurant in Toronto. The food was fantastic and spokespeople representing every aspect of the industry were present to tell their story and answer questions. While I learned a lot, I left the event feeling unsure about how to evaluate the many aspects of aquaculture. After all, it’s not really just one topic but dozens since different methods and species face different challenges.

I turned to Theodora (Teddie) Geach, Ocean Wise’s Eastern Coordinator, to help sort out my thoughts. Not only was she eager and able to answer my questions, she did such a great job that I’m excerpting her email here so that you can learn more about the pros and cons of Aquaculture, too!

“Aquaculture is the fastest growing food production system in the world and definitely has benefits if done correctly. It has the potential to relieve the pressure from over-exploited aquatic resources; however, it also has the potential to negatively impact the surrounding environment and wild fish stocks.

Five main criteria need to be taken into consideration:

1. Use of marine resources: This would be for example, the amount of wild fish used in fishmeal. If you’re feeding your farmed fish with more wild fish than you’re producing, you’re still putting pressure on the wild fish stocks. Ideally more fish protein is produced using aquaculture, than is used to facilitate it.

2. Risk of disease and parasite transfer to wild stocks: Since farmed fish are confined, they generally live closer together than they would in the wild. This increases the risk of disease and parasites. Therefore, the stock density needs to be considered. As I’m sure you know, with farmed salmon there is the issue of sea lice which can be transferred to juvenile wild salmon, increasing their mortality. In order to reduce this risk, antibiotics are sometimes added to the water which can result in stronger more resistant strains. However, today in BC, you need to get approval from a veterinarian before using any antibiotics. (I’m not sure if this is the case on the east coast as well.)

3. Risk of escapes to wild stocks: Most salmon farms are open-net pens or floating net pens in the ocean, therefore there is the risk of escape. These escaped fish can then compete with wild stocks for resources and may reproduce with wild stocks, thus reducing their genetic viability.

4. Risk of Pollution and habitat effects: These open-net pens can have a significant impact on the surrounding environment since anything added to the water is able to leach out. There can be a build-up of excessive fish feed and feces, which pollute the water and creates a very anoxic environment where nothing can grow except for sulfur loving bacteria. These open-net pens are usually in sheltered coves to protect the nets from extreme weather, but this also means that there is no current flowing through to flush out all the build-up of chemicals and feces, etc.

5. Effectiveness of the management regime: As with any fishery, there needs to be an effective management system in place to ensure that aquaculture practices favour conservation of the environment. For example the use of licensing to control the location, number, size and stocking density of farms; the existence of better management practices; and regulations for release of chemicals into the environment.

So for Atlantic salmon and cod farms, if they are able to address all these issues and support their claims with the data and sound science they would be considered sustainable. However, it is difficult for any open-net pen farm to address all these issues sufficiently.

6. The best option for farmed fish is a land-based, closed containment system. This way there is no risk of transfer of disease to wild stocks, no risk of escapes and you are able to treat and control the effluent water. An excellent example of one of these farms is in Agassiz, B.C. where Bruce Swift as created a land based Coho salmon farm. He is able to treat the effluent water and collect the solid waste, which is then used as fertilizer for garlic and bean crops. The wastewater is used to grow wasabi, watercress and algae. The algae are then used to feed his freshwater crayfish.

In addition to the land based farmed salmon that Bruce Swift is doing, there are some species of fin-fish which are better candidates for farming than others. Other examples of sustainable-farmed fish would include raceway-raised rainbow trout, land based arctic char and land based catfish

Tilapia offers and excellent case study: tilapia provides more protein than it takes to raise it and are relatively resistant to disease. Tilapia are also vegetarian and can be raised on soy protein and rice, which obviously does not put any pressure on the wild fish stocks. However, you still have to be careful where you get farmed tilapia. The best choice is tilapia farmed in the US, which generally uses land-based, closed containment systems. Farmed tilapia from Central America can also be found in our markets. In CA, regulations can vary and the farms may not always be land based; likewise, farmed tilapia from Asia would generally always be considered unsustainable since they are mostly produced in open-net pens.

7. In general farmed shellfish is considered sustainable. This is because they are filter feeders, eating the plankton out of the water column, so they don’t need supplemental feed and don’t put pressure on wild fish stocks. They can even improve the water quality as they clear excess plankton. Shellfish such as oysters and mussels are often grown on suspended cages or in bags off the seafloor so there is little damage when they’re harvested. (This is called off-bottom culture.) Clams can be farmed on-bottom and there can be an issue if they are harvested by dredge. However, the impact of farmed dredging is far less than dredging wild clams.”

Thanks Teddie! I think my readers will agree that you’ve done a great job explaining the benefits and pitfalls of current aquaculture practices!

Do any of you have questions about seafood? If so, jot them below and I’ll invite folks from the CAIA and Ocean Wise to pop in and answer your concerns.


16 Responses to Aquaculture: Fishing for answers

  1. Rosa says:

    Interesting! Thanks for the info.



  2. Thanks for this, Dana! Interesting about the land-based farmed fish. Over-fishing is still a huge issue and not likely to be balanced by artificial means.

    Would moratoriums on certain endangered / threatened species help (assuming all countries respected them)? If so, how long would it take to let nature regain some of the lost ground (sorry for mixed metaphors). What stocks would it help and which ones are too far gone to save?

    Thanks for answering my questions.

    • Teddie says:

      Hi Charmain,
      Those are some good questions. I’ll do my best to answer them for you.
      Fishing moratoriums on endangered species would definitely help to relieve some of the fishing pressure, but as you said it can be difficult to ensure that these are respected. Unfortunately poaching continues to be an issue so measures need to be in place to enforce these moratoriums.
      A moratorium on a single fishery may reduce the fishing pressure on that particular species, however this doesn’t mean that fishing in that area will cease completely. If intensive fishing for different species continues, this can still impact the endangered species in question due to extensive habitat damage by bottom trawling for example.
      It has been over sixteen years since the moratorium was placed on the Newfoundland cod fishery back in 1992 and yet the cod populations have still not recovered to the numbers they were at before the 1980s. This is partly due to the fact that bottom trawling continues to take place in the cod’s spawning grounds. These trawls destroy the seabed in which juvenile cod hide until they grow large enough.
      I believe if an area of the ocean is left undisturbed for even a couple of years the corals and fish and other sea life start to come back. However, I’m not sure how long it would take for a specific population to replenish; it would depend on the species.
      I hope this helps to answer your questions!

  3. Diva says:

    Very interesting post, Dana, and I really enjoyed reading the information. I’m generally not much of a seafood eater, but I do like to stay informed.

  4. Can I ask one more question? What’s happening internationally with bottom trawling? Is there a move to ban it? Are any countries refusing to do it?

    It seems such a destructive process I can’t believe it’s allowed. But I can be very naive about such things.


  5. danamccauley says:

    From the “About Dana” thread comes this great comment:

    Patrick Says:
    October 21, 2009 at 5:49 pm | Reply edit
    Two things:
    1) I am in my 60s, have fished and eaten seafood a lot but have never heard of “tilapia” fish before. Is this a new name for a fish I’d be familiar with by another name, or is this a new type of fish?
    2) I’ve always avoided eating farmed fish. But you mention the good fish farm of Bruce Swift out in Agassiz.
    Where does he sell his wares?

    danamccauley Says:
    October 21, 2009 at 6:15 pm | Reply edit
    Hi Patrick,

    I’m moving your good questions to the thread where we chatted about Aquaculture so that everyone involved in that conversation can see the answers. I’ll email you as well so that you get the info you need first hand and don’t have to chase around here in my blog.


    • danamccauley says:

      Patrick, here’s what I found out about tilapia:

      Tilapia, several species and their hybrids of Oreochromis, are the second most important group of farm raised fish in the world. Tilapia farming and consumption are rapidly increasing in the US. Tilapia is now the fifth most popular seafood consumed in the United States ( so it’s not surprising that you’re seeing it now more than ever before.

      According to Seafood Watch (

      Native to North Africa, tilapia is a hardy, freshwater fish that tolerates a wide range of water conditions. This means it’s easy to farm, but it also means it easily invades many habitats and threatens native fish populations.
      U.S. farmed tilapia is the “Best Choice,” with tilapia from Central and South
      America as a “Good Alternative” to other imported product (ie from China/Taiwan).

      As for Bruce Swift’s Salmon, I’m not sure where it is sold but here’s contact info for his company:
      Tri-gen Fish Improvement Ltd.
      4291 W 16Th Ave.
      Vancouver, British Columbia V6R 3E5

      I know that C Restaurant in Vancouver uses Bruce’s salmon but to be honest, I’m not sure if it is sold at retail or just to chefs.

  6. Float says:

    We do need to do something about dwindling fish stocks, and overfishing and fish farming is definately one option. One problem is that there’s really no comparison between, say, the taste of farmed salmon and wild salmon.

  7. Ruth Salmon says:

    Hi Dana,

    Many thanks for attending our recent Farmed Seafood Extravaganza in Toronto – it was very nice to meet you. I also appreciated you taking the time to write about aquaculture in your blog.

    As you point out, aquaculture – the farming of finfish and shellfish – takes the pressure off wild stocks and is helping feed a growing global population.

    However, I thought you might appreciate this additional information, broken into categories according to your blog posting, to help address some of the uncertainties you have towards our industry practices.

    Use of marine resources: With constant improvements in feed, and improved husbandry, Canadian salmon farmers only require an average of 1.5 kg of feed to grow 1 kg of salmon. The amount of wild fish meal and oil used in feed is being reduced, and replaced by plant proteins, with no significant reduction in heart-healthy omega-3 fatty acids in the fish. Canadian salmon farmers are leading the way in feed technologies, and most use approximately 30 percent fish meal and oil in each kg of feed. That means only 0.5 kg of wild fish meal and oil are needed to grow one kg of farmed salmon. Looking at the big picture, growing fish is much more efficient that raising animals on land where it takes 3 to 10 times as much feed to produce an equivalent amount of food.

    Risk of disease and parasite transfer to wild stocks: Sea lice numbers on farmed salmon are monitored and managed to minimize possible transfer to wild populations. This work is audited by provincial authorities. Salmon farms are sited in areas where water currents provide optimal conditions for fish well‐being and environmental sustainability. This includes avoiding sensitive wild salmon habitat, such as coastal fish spawning and nursery areas. Every farm is monitored regularly. If required, veterinarians prescribe medication to remove the lice from all salmon on the farm.

    Risk of escapes to wild stocks: Escapes of farmed salmon have been drastically reduced. It is thanks to the vigilance of salmon farmers that the North Atlantic Salmon Conservation Organization has listed aquaculture as one of its lowest threats to wild salmon populations. Regarding the BC industry, it’s important to point out that farmed Atlantic salmon are poorly adapted for survival in the wild. When escapes do occur, farmed Atlantic salmon have not been shown to colonize indigenous rivers.

    Risk of Pollution and habitat effects: All proposed aquaculture developments are subject to an intensive environmental review – including the Canadian Environmental Assessment Act (CEAA) – to ensure that the development will not negatively impact ocean and freshwater habitats. Farms can only be sited in areas where water currents provide optimal conditions for fish health and environmental sustainability. Once farming begins, environmental monitoring of aquaculture sites is conducted on a regular basis. Monitoring involves state-of-the-art computer modeling, water quality sensors, satellite imaging and Geographical Information System technology coupled with sea floor sampling and video recording.

    Effectiveness of the management regime: The environmental performance of the Canadian aquaculture industry is closely monitored through a rigorous framework of 73 pieces of federal and provincial legislation. Industry is also taking responsibility for environmental sustainability through the development of Codes of Practice for both finfish and shellfish operations. These Codes are being developed by industry participants, through their associations, to meet or exceed international environment, health and safety standards – and are instilling a high level of producer diligence with respect to the environmental performance of their operations.

    Closed containment: Although there are various pilot projects for growing salmon in closed containment, none have so far proven commercially viable or environmentally sustainable on a large scale. For instance, a four year project in the Bay of Fundy to determine the feasibility of growing salmon in a closed containment system concluded the open ocean provides the best environment for growing salmon in an environmentally sustainable manner. However, industry continues to invest in research and development in all areas of aquaculture.

    Overall sustainability of farmed seafood: By definition, all farmed food – whether grown on land or in the water – is sustainable compared to hunting and gathering. With the UN forecasting a global increase of 40 million tonnes of seafood consumption by 2030, aquaculture will play an even greater role in feeding the planet. The aquaculture industry cannot succeed unless we use sound ecological practices and manage our resources. In Canada, farmers are committed to ensuring that our farms are managed in a way that protects the environment, and provides economic benefit to coastal communities.

    If you have any more questions, please let me know.


    Ruth Salmon
    Executive Director
    Canadian Aquaculture Industry Alliance.

  8. danamccauley says:

    Hi Ruth,

    Thanks so much for taking the time to write a thoughtful, lengthy response! I’m going to read it closely and come back and make more comments later.


  9. Teddie says:

    Hi Ruth,
    I just have some questions with regards to your response on Dana McCauley’s blog. I am by no means an expert on aquaculture and still have much to learn. I would appreciate any information you can provide.

    Use of marine resources: Are there currently any regulations in place on what type of fish is used for feed? How it was caught and where? My concern would be if the fish used for feed were coming from a fishery that is already considered overfished or at risk of being overfished.

    Risk of disease transfer: How are the numbers of sea lice monitored and managed to minimize the transfer to wild populations?
    Sea lice is not the only disease that farmed salmon are prone to. Farmed salmon are in much closer proximity to one another than they would normally be and these conditions are condusive to disease outbreaks. Are there any regulations on maximum fish density to reduce this risk and if so have there been studies to prove that this density standard reduces the incidence of disease out break?

    Risk of escapes: How have the numbers of escapes been reduced?

    Risk of pollution and habitat effects: What type of things does the CEAA look at to ensure that there will be no impact on the ocean and freshwater habitats?

    I would appreciate any answers you can provide. Thanks!

  10. A bad day of fishing is better than a good day of work.

  11. C.Naim says:

    Yes,you were right. Deep-sea fish farming conteminated with PCB and other heavy metal which will effect the end user,us.

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