Most people have eaten cod at some point in their lives, but up until recently, it was usually Atlantic cod. However, because of many years of overfishing (think Gorton's fish sticks and McDonald's Filet-O-Fish), now only the Icelandic fishery remains in healthy condition for cod. But because the demand for cod—and its cousin the pollock fish—continues to grow, the North Pacific fisheries have ramped up the production of similar species. Today, nearly every fish stick, fast-food, or breaded fish you will find in the U.S. is either Pacific cod or Alaska pollock.
Both fisheries are in excellent shape, so these fish are both economical and sustainable choices for seafood lovers. Pacific cod and Alaskan pollock are white, low-fat, mild fish. They typically come as skinless fillets and are commonly sold frozen. Both have a coarse flake when cooked and their bones make excellent stock, but the difference is in their texture: Pacific cod is nearly identical to its Atlantic cousin, just slightly less firm; pollock fish, on the other hand, is soft.
Cooking Pacific Cod Fish
Pacific cod is an excellent substitute for any recipe that calls for Atlantic cod. It is what you will get in most restaurants these days when you order cod. Pacific cod is delicious baked, fried (especially batter-fried as in fish and chips), sautéed, and steamed. Pacific cod is also good in fish soups and chowders as it will remain firm.
Cooking Alaskan Pollock Fish
Alaskan pollock makes fine fish sticks and fish cakes and is good steamed. It is passable as fish and chips, but this is not the ideal preparation. Don't broil it, because if you make the slightest miscalculation on timing you could wind up with dry fillets. Also, do not put Alaskan pollock in a fish soup unless you intend to purée the soup as the fish will practically dissolve in the broth.
Another way to eat Alaskan pollock is as surimi, or imitation crab. You have probably 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, although it really doesn't.
Buying and Storing Both Fish
Both Pacific cod and Alaskan pollock freeze very well, and since both are from far-off waters, it is best to always buy frozen unless you can be assured that the fresh fish has never been frozen before.
Please remember—do not eat either fish raw! They can sometimes harbor little parasitic worms that will pass on to you if you eat the fish uncooked, which is 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 fish markets remove them when selling either fish fresh.