Fish, Omega-3 Fatty Acids, the Environment and Your Health

High mercury fish include swordfish, shark, mackerel, tuna. Some studies have found that farmed salmon have higher levels of pesticides than wild salmon. Bottom line: Limit yourself to 12 oz fish per week (from stores or restaurants, not local lakes). Vary your intake. Check local advisories periodically. Choose fish lower on the food chain, which include cod, whitefish, pollock, mahi-mahi, ocean perch, halibut, haddock, flounder, sole, and all shellfish.

The Wellness Letter (4/04) notes that farm grown salmon is high in PCBs (organic pollutants that MAY cause cancer). They recommend eating no more than 12 ounces of fish/wk, and vary your choices (eg salmon, tuna, shellfish). The lead researcher of this recent study of PCBs suggests eating no more than 8 ounces of farmed salmon per month. Most canned salmon is wild, so alternating fresh salmon (likely farmed) with canned salmon may make some sense. Remove the skin and the fat under the skin when having fresh salmon, as this is where the PCBs accumulate; broil, bake, poach or grill the fish, as this will also allow the fat (and PCBs) to drain off (plenty of omega-3 fatty acids will remain).

Here is the low-down of various fish (from Nutrition Action Health Letter, June 2004):

Here is another summary of various fish with estimated levels of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
FishEPA plus DHA gram per 3 oz serving (edible portion)Amount of fish (oz) required to provide about 1 gm of EPA plus DHA per day
Farmed catfish0.1520
Wild catfish0.2015
Alaskan king crab0.358.5
Halibut0.40 to 1.03 to 7.5
Atlantic herring1.712
Pacific herring1.811.5
Mackerel0.34 to 1.572 to 8.5
Atlantic farmed salmon1.1 to 1.81.5 to 2.5
Atlantic wild salmon0.9 to 1.62 to 3.5
Sardines1.0 to 1.72 to 3
Shrimp, mixed species0.2711
Fresh tuna0.24 to 1.282.5 to 12
White tuna (canned in water, drained)0.734