The facts on fish

CHOICE investigates the benefits and risks of eating fish.
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  • Updated:19 Oct 2008

04.Fresh, frozen or canned?

When you’re buying fish, what do you choose? Which fish give you the most omega-3s and least toxic chemicals while coming from a sustainable fishery? In the table we’ve compared some of the species of fish you’re likely to find at your local shopping centre or fish co-op.

Fresh fish

Fresh fish are best for flavour and texture, except when they’re really frozen fish that have been “thawed for your convenience”.

  • Swordfish is an excellent source of omega-3s but is best avoided because of its relatively high mercury content and doubts that it’s being sustainably harvested.
  • Atlantic salmon is a good choice if aquaculture doesn’t worry you for environmental or other reasons.
  • There are Australian species that are harvested sustainably and contain healthy levels of omega-3s. (See the table for details.)
  • Most shops also have basa, a species of catfish farmed in the Mekong Delta in Vietnam. It’s cheap but has very low levels of omega-3s and will have been frozen.

Frozen fish

Packaged frozen fish is a convenient standby that’s quick and easy to prepare. Again, Atlantic salmon is the best choice for omega-3s, but if it’s frozen it might have been harvested from sea cages which can have negative effects on the environment. Hoki is used most often in frozen fish portions. It has lower levels of omega-3s than Atlantic salmon, but still useful amounts. The New Zealand hoki fishery has been certified by the Marine Stewardship Council, so check the label for that logo (see Labels and logos). Other hoki fisheries haven’t been certified and may not be as carefully managed.

Canned fish

Can of red salmonHerring, sardines and mackerel are outstanding for omega-3s. These small fish from northern waters can be harvested sustainably because they’re fast-growing and low in the food chain.

Canned Pacific salmon is also a good source of omega-3s. Also called red or pink salmon, these fish are different species from Atlantic salmon. They’re harvested from the wild, using nets. The Marine Stewardship Council has certified Alaskan but not the Canadian Pacific salmon fisheries, and some brands of canned salmon carry that logo.

Fish miles

Most canned fish comes from the other side of the world, raising the issue of food miles. But preserving food in cans uses less energy and creates fewer greenhouse gas emissions than freezing. It takes more energy to make the can than the cardboard packaging, but frozen foods require more energy for processing and distribution.


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