I'm an infrequent fish eater (yuk, it makes the house smell fishy) and daily fish oil user. I look carefully at the composition of Omega 3s and especially want Eicosapentaenoic Acid (EPA). My guide for this is Barry Sears, author of the Zone Diet books and a high-level ivy-league biochemist who trains Olympic athletes.
If you use fish oil, you might check out Natural Factors RxOmega-3 Factors, pharmaceutical grade, with 630 mg Omega3 in each cap, 400 of which is EPA. Nice product! I found it at www.iherb.com at a very good price.
Also, because I live in the gloomy northwest, I take Cod Liver Oil in the winter, buy Carlson's Norwegian 1000 mg, supposedly the most pure product available. So that also gives me an additional 240 mg of Omega 3. Also available at iherb.com at a nice discount.
And to think I used to live in Florida and had a vacation house in Key Largo. Who worries about fish oil there?