The World's Most Favorite Fish:
Nearly everyone has eaten cod at some point in their lives, but until recently it would have been Atlantic cod. Now only the Icelandic fishery remains in healthy condition.
Demand for cod and its cousin the pollock continues to grow, however. The response to this demand has been to ramp up the North Pacific fisheries of similar species to the Atlantic cod and pollock. Now nearly every fish stick, fast-food or breaded fish in the nation is either Alaska pollock or Pacific cod.
Despite this, both fisheries are in excellent shape, which makes these fish both economical and sustainable.
Pacific cod and Alaskan pollock are white, low-fat and mild. They typically come as skinless fillets and are commonly sold frozen. Both have a coarse flake when cooked. Bones from either fish make excellent stock.
The difference is in texture: Pacific cod are nearly identical to their Atlantic cousins, although they are slightly less firm. Pollock, on the other hand, are soft.
Alaskan pollock makes fine fish sticks and fish cakes, is good steamed and is passable as fish and chips. Don't broil it, because if you make the slightest miscalculation you could wind up with dry fillets.
Another way to eat Alaskan pollock is as surimi, or imitation crab. Many of you have eaten it in a California roll at mid-range sushi bars; often the "crab" in this crab-and-avocado roll is actually Alaskan pollock, processed into surimi. It is supposed to taste like snow or king crab; it doesn't, but is OK for what it is.
Pacific cod, on the other hand, is an excellent substitute for any recipe that calls for Atlantic cod. It is what you will get in most restaurants when you order cod.
Pacific cod are excellent baked, fried (especially batter-fried), sauteed and steamed. Pacific cod is also excellent in fish soups or chowders. Do not put Alaskan pollock in a fish soup unless you intend to puree it -- the fish will practically dissolve.
Both fish freeze very well, and since both are from far-off waters, I would advise you to always buy it frozen, unless you can be assured that the fish had never been frozen before.
Oh, and one more thing: Do not eat either fish raw! They can sometimes harbor little parasitic worms that will pass on to you if you eat the fish raw -- that's why you will not see cod on a sushi menu. Although they don't die when the fish is frozen, the worms become harmless and are practically invisible once cooked. Reputable fishmarkets remove them when selling either fish fresh.