In order to give us the ‘low-down’ on fish farming, we asked expert Dr. Stefanie Colombo from Dalhousie University in Nova Scotia, Canada. Dr. Colombo is passionate about marine life and an expert on aquaculture.

What is the difference between wild and farmed fish?

Dr. Colombo: “Wild fish grow naturally in ponds, lakes, rivers, and oceans, and are then caught for human consumption. Farmed fish are grown entirely in ‘captivity’ from egg to harvest. Another form of farming is called ‘ranching’ where young fish are caught and then raised in cages until it is time to harvest. For example, tuna is often ranched rather than farmed, whereas salmon are farmed.”

How are farmed fish contained? In nets or ponds or tanks?

 Dr. Colombo: “Farmed fish are contained using different methods, sometimes depending on the species and their natural habitat, either freshwater or marine. In Canada, we grow fish in nets pens, ponds and tanks. Sometimes a combination of methods are used. For example, Atlantic salmon are raised in tanks for the first part of their life, until they are about 100 grams in size, then they are transported to net pens in seawater, in coastal areas in Atlantic Canada and British Columbia. This method is used because this resembles the natural life cycle of salmon, where the first part of their life is spent in freshwater and then grown to maturity in seawater. Salmon can also be grown completely land-based in tanks without the net pens in seawater. In Canada, we also grow some species in ponds, like striped bass, but in other parts of the world (Asia, Africa) pond culture is the most popular way to grow certain species, like tilapia and shrimp.”

Are organic fish wild or farm raised?

Dr. Colombo: “Organic fish are farm-raised organic. That might be counter-intuitive to some people, because what could be more organic than a fish that came right from the sea? But part of the organic certification ensures the methods and practices of how the animal was raised (or the plant was grown) are of organic standards, which is impossible to ensure when catching fish in the wild. Canada’s organic aquaculture standard prohibits the use of antibiotics, herbicides and genetically modified organisms. About 3% of Canadian seafood producers have chosen to pursue organic certification. These include producers of Atlantic salmon, Pacific chinook salmon, sturgeon and caviar, sablefish, trout, mussels, and seaweed.

“Organic farm-raised shouldn’t be confused with sustainability certification that you often see on wild fish packaging (e.g., Ocean Wise ®, Marine Stewardship Council -MSC Certified). Sustainable seafood helps to relieve the pressure on overfished species while leaving enough fish in the ocean, respecting habitats and ensuring people who depend on fishing can maintain their livelihoods. These labels ensure that the seafood is sustainable (wild or farmed), but they are not necessarily organic. Some farmed seafood can be both sustainably and organic-certified.”

 What is the nutrition profile difference between organic, wild and farmed?

 Dr. Colombo: “The nutritional profile of wild vs. farmed vs. organic farmed is not very different when you compare fish of the same species. The most important factor to consider is the composition of the diet and where they are grown (commercial feeds in culture vs. natural prey in the wild), which has an influence on the nutritional content of the fillets. In general, because of this variability, there is not a sound scientific conclusion, because it can depend on where the fish was caught, or the farm it was harvested from.”

Learn more about the food that farmed fish eat.

How can we ensure that the organic-labelled fish we buy are truly organic?

Dr. Colombo: “Organic standards in Canada are set by the Canadian Food Inspection Agency (CFIA). Farmers must adhere to these standards, but also need to create and maintain a detailed organic management plan, which describes all practices, record keeping, etc. Organic seafood producers are also audited by the CFIA-accredited organic certifier. This ensures that the organic labelled seafood is regulated, monitored, and traceable.”

Farmed fish are raised in different types of systems, sometimes depending on the species and their natural habitat, either freshwater or marine. Certified organic fish are always farm-raised. The nutrition profile is similar between wild, farmed and organic fish in the same species.

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What does farmed fish feed look like?

Dr. Colombo: “The feed looks very similar to the kibble you would feed to your pet dog or cat. It is an extruded pellet. We actually eat lots of extruded foods – think breakfast cereals, like puffed corn or corn pops. The process is the same.”

What are the primary ingredients?

Dr. Colombo: “The ingredients can vary, what is most important is that the nutrients in the ingredients meet the requirements of the fish. So, the ingredient itself is not as important as the nutrient it supplies. For example, Atlantic salmon need about 50% protein and 25% fat. This can come from different ingredients, but, some of the most common ingredients are based from corn, poultry, canola, soy, wheat and fish.”

People seem to be concerned about fish meal and fish oil in farmed fish diets. Why is this a concern?

Dr. Colombo: “Using fish meal and fish oil in diets for farmed fish is necessary, but there is concern because these ingredients are sourced from wild fish populations, such as herring, sardines, anchovies, and menhaden. A majority of fisheries have been at their sustainable limits for the past twenty years – they are not declining – but they are not growing either. This is a concern as the human population grows and we need more healthy protein and fats to support our nutritional needs. Aquaculture is helping to meet our seafood demand (60% of our seafood will be from aquaculture by 2030), but when it depends on wild fish, this is a constraint on the fisheries and on the ability for aquaculture to meet the needs of the human population. We are getting more efficient at making fish meal and oil from what we already have, as opposed to catching more fish – for example, the heads and tails of fish that we don’t eat are a perfect source of fish meal and oil for farmed fish. But it is likely that in the future, the aquaculture industry will not need fish meal or oil at all to produce healthy, high quality farmed fish.”

How can we decrease the amount of fish meal and fish oil in their diets?

Dr. Colombo: “Researchers and the aquaculture feed industry have made strides in reducing the levels of fish meal and fish oil that are included in the diet. There are hundreds, if not thousands, of studies that have tested new ingredients that can be used for growing different farmed fish species. Again, the important thing is providing the correct nutrients, more than it is about the ingredients. Fish meal and oil have decreased in commercial diets from about 70% of the diet to about 25% of the diet. Plant-based ingredients have been used to supply some of the protein and fat to replace fish meal and oil. Still, some fish meal and oil need to be used, because they supply nutrients that are not made by plants – like the omega-3’s (eicosapentaenoic acid – EPA, and docosahexaenoic acid – DHA), which are needed for fish health. Research efforts continue so that we can feed completely vegan-diets to any farmed fish species that does not compromise their health and well-being.”

Do different varieties of fish eat different foods? If so, how different?

Dr. Colombo: “Yes, different species of fish have different nutrient requirements. Some fish are naturally carnivores – they eat other fish – like salmon, rainbow trout, halibut, tuna. Some fish are naturally herbivores – they only eat plants – like carp. Some fish are omnivores – eat both plant and animal matter – like tilapia, catfish. The nutrient requirements of the species, and what they are able to digest and absorb, helps to determine the types of ingredients that can be used in their diets.”

Can some fish be organic? Do organic fish eat different foods?

Dr. Colombo: “Yes, farmed fish can be raised organically. Their feed is an important part of the organic regulations. The feed must be compatible and comparable to the species’ natural diet. Where fish meal and fish oil must be used, there are preferences in the Canadian Guidelines about the source of fish meal and oil that is used, such as using trimmings (i.e., heads and tails) from organically raised fish for human consumption or from wild caught fish that were already caught for human consumption. For salmon, there are restrictions on the type of pigments that are included in the feed, they must be from a natural source. They are also raised organically because they are raised without use of antibiotics, with more focus on preventative methods for rearing.”

Learn more about how fish are raised.

Farmed fish eat feed that has been developed to provide the nutrients they need. Different species have different nutrient requirements. Most feed contains fish meal or oil and researchers are developing many new options for feed.

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