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.