>>Cheyenne Loon asked how you tell if fish oil (e.g. salmon) is rancid?
>>Presumably it should have a bit of a fishy smell even when fresh.

Fresh cod liver oil, if properly pressed, should not smell unpleasant.  I
have tried a number of brands over the years.  I suggest buying only
Carlson's, preferably lemon flavored.  (Many kids I know will eat Carlson's
cherry or mint cod liver oil off a teaspoon daily, with a little prompting
from mom.  We don't drink the oil--we use it by the teaspoon in our house.
my husband and I use lemon flavored cod liver oil spooned over salad,
steamed broccoli, spinach, or white meat fish, with a dash of lemon juice,
mustard, black pepper, and a pinch of dried herbs if you like olive oil,
making a sort of vinaigrette to use immediately. )

Buy it in small bottles; keep under refrigeration; use it up promptly (1-2
tsp./day); don't heat it or leave it out long; fill the bottle with filtered
water as you use up oil, to displace the oil and prevent oxidation.  This is
the only brand that I have tried that does not had an unpleasant and strong
odor and flavor.   Many dozens of people have confirmed the quality of this
brand and the palatability.  A naturopathic physician I know also finds this
to be the best brand.  My husband and I both love fish--esp. salmon,
mackerel and other oilsy, cold water fish---however, we both found Twinlab
fish oil to be so strong that it was unpleasant.

Our local fish market will order in wild salmon on request; they mostly sell
farmed salmon (which is dreadfully low in omega 3s and high in omega 6s)
because people want uniform flavor and appearance and my fishmonger tells me
that wild salmon is so unpredictable in this respect.  The price is
practically and often the same for wild and farmed at this fish market which
also services restaurants, including sushi bars!!!

Your local health food store should be able to order Carlson's brand cod
liver oil.   If not, do a web search for Carlson's and see if you can mail
order it.

Re:  Tuna.  The total number of grams of fat per reasonable serving, make it
inferior as a significant source of EFAs.  Of course, you could spoon on 1-2
tsp. cod liver oil at the table, or cook it in fish blubber.  :-))

TUNA 3 oz. raw
Bluefin, 4.2 grams fat
Skipjack, 0.9 grams fat
Yellowfin, 0.8 grams fat

TUNA, 3 oz. cooked, canned, in h20
0.4 grams fat

If you can get tuna packed in sild (fish oil), a rarity, that is a good bet.
Check gourmet or specialty food stores.

Cheers,
Rachel