Content Last Updated January 2013
Health practitioners have good reasons to encourage the consumption of fish and seafood. These foods are rich in omega-3 fatty acids, low in saturated fat, high in protein, and has been shown to have numerous benefits for cardiovascular health and inflammatory conditions. As we consume more of this desirable protein we need to start looking at the sustainability of these recommendations. Up to 35% of Australian seafood comes from aquacultures, (fish farms) including prawns, oysters, tuna and salmon. What do we need to know about fish farms to ensure we are making the most sustainable option?
What Is Marine Aquaculture?
What Are Fish Farms?
Marine aquaculture, also known as fish farms, uses large netted cages floated underwater in estuaries or bays to hold schools of fish.
What Do Farmed Fish Eat?
Fish raised in this environment are then usually fed a diet of fish meal, which is made from small wild fish such as mackerel and sardines, and usually mixed with grains. It can take up to 12 kilograms of fishmeal to produce 1 kilogram of farmed tuna and, and up to 4 kilograms of fish meal to produce 1 kilogram of farmed salmon.
How Fish Farms Affect Our Health
Farmed Fish and Omega-3 Fatty Acids
There are concerns that farmed fish contain more total fat but less omega-3 fatty acids, the good fats. The omega-3 content is highly dependent on the fish’s diet. Wild fish get their omega-3 fatty acids from omega-3 rich plants including algae and plankton. Farmed salmon may be fed a mixture of plants, grains and fishmeal, so the omega-3 content can be variable. New fish food is being developed that uses protein derived from grains and oilseeds, such as soybeans.
Farmed Fish And Higher Concentration of Toxins
Reports are mixed on the content of toxins including PCBs in farmed fish versus wild fish. PCBs have been linked to developmental abnormalities. Why would farmed fish be higher in PCBs? Possibly due to eating a diet of wild fish from a young age and thus ingesting a greater amount of chemicals as compared to wild-caught fish that feed off krill until they are older.
Antibiotics and Farmed Fish
Farmed fish are fed antibiotics to help ward off diseases caused by their cramped living environment. In Canada, antibiotics can only be used when they are required to fight disease, never to stimulate growth. The open nature of fish farms allows for antibiotics to flow into the ocean. This is a concern to human health as it could build antibiotic resistance, which could lead to situations where antibiotics no longer work for human treatment.
How Aquaculture Impacts Our Environment
The Effect of Aquaculture On The Land
Aquaculture can lead to damage to our coastlands, affecting biodiversity and reducing mangroves, coastal wetlands and coral reefs. Of even greater distress is the water pollution caused by fish farm wastes such as uneaten fish food and excrement, which may contain antibiotics, which are passed out to the open ocean.
Farmed Fish and Sea Lice
When farmed fish escape there is also the risk of spreading disease or interbreeding with wild fish, causing genetic pollution of the wild species and potentially reducing their ability to survive. In Norway studies have shown that a large number of wild salmon are dying from sea lice infestations they contracted when migrating past salmon farms.
The Sustainability of Australian Salmon
Is All Australian Salmon Farmed?
Almost all the salmon purchased in Australia is farmed Atlantic salmon, which is not a native species and is often marketed as Tasmanian salmon. There are concerns about the amounts of antibiotics used in Australian salmon and the high amounts of PCB and dioxins. Often synthetic food colouring is used to give the salmon flesh a pink hue which is often seen in wild salmon due to their diet of krill.
What About Wild Australian Salmon?
Wild Australian salmon does exist but is not readily available. The South Australian Fishery, which catches the native Australian salmon, has been recognized as using sustainable fishing practises with relatively small ecological impact.
Is Freshwater Aquaculture Better?
The Sustainability of Freshwater Aquaculture
Fish raised in inland ponds and dams have a less environmental impact due to the enclosed system they are raised in. Not only is there less damage to the coastline, but there is also less chance of antibiotics or disease escaping to the wild populations.
Which Is The Most Sustainable Freshwater Aquaculture Fish?
Fish such as carp, catfish, crayfish and eels do not require fishmeal at all. Other small herbivorous fish may only need 2 kilograms of feed to produce 1 kilogram of meat. It is important to note that some freshwater carnivorous fish like trout and barramundi are fed fishmeal pellets, which can have a harmful impact on the wild fish populations that are used to make the feed.
When Is Aquaculture More Sustainable?
Aquaculture has come along way, and with our increasing population, we can’t fully depend on the ocean’s stores to feed us. There are many different types of aquaculture, here are some of the most sustainable types of aquaculture:
- Wild-caught scallops are often fished using seafloor dredges or trawls which are invasive and damaging and result in significant bycatch. Choose farmed over wild scallops.
- Wild abalone is also fished using methods that have a significant impact on local ecosystems. Choose farmed over wild abalone.
- Oysters and mussels are filter feeders, gaining nutrients from microalgae and other plant matter in the water around them and therefore don’t require any extra feed. Both farmed oysters and mussels are good choices with little environmental impact.
- Squid, cuttlefish and octopus are caught using sustainable fishing methods and are generally fast-growing robust animals. However, canned baby octopus from the Gulf of Thailand is overfished and should be avoided.
- Crayfish (Yabbies) are farmed in small ponds and tanks and have minimal impact on the environment. Wild fisheries are a concern due to the degradation of our streams and rivers which has had a significant effect on wild yabby stocks.
There are many environmentally sustainable seafood choices out there, but it is up to us the consumer to ask the necessary questions. The more we as consumers ask about different species of seafood, the more retailers will start to listen. As a general rule, avoid sea-farmed fish and choose freshwater herbivorous farmed varieties instead. Not only do they have less impact on the environment, but they will contain fewer chemicals and pollutants.
Rachel Dickens is a Registered Dietitian and Certified Diabetes Educator. She graduated with her Masters in Nutrition and Dietetics in 2010 from Griffith University and is currently a PhD student at UBC. She strives to provide evidence-based nutrition information with a focus on Indigenous Food Sovereignty while sharing diabetes-friendly recipes and tips for diabetes prevention.