Atlantic Cod (Gadus morhua), Greenland Cod, (Gadus ogac) and Pacific Cod (Gadus macrocephalus) are robust, meaty fish that inhabit cold waters near the bottom and are voracious eaters of anything that can fit in their large mouths. The three “true” cods as well as the other cod-like fish in the genus Gadus all share similar characteristics, but the Atlantic Cod is historically the largest and easily recognized by its large head, three dorsal fins and prominent lateral line.

The Pacific cod prefer deeper water and have a more brown or gray coloring, with less variation than the Atlantic cod. Pacific cod typically top out around 10 pounds, but Atlantic cod can to nearly 100 pounds. The Greenland cod also known as the ogac, is of only minor commercial importance, but is more similar to Pacific cod than Atlantic.
How They are Caught

Atlantic cod are mostly harvested with otter trawls, gillnets and longlines. Pacific cod are caught trawlers, longliners and also by fish trap – “pots.” At the dock, cod is graded by size with scrod being the smallest at under 3 pounds, market cod go up to 10 pounds, then large cod, and anything over 25 pounds are known as jumbo or “whale” cod.
There has been some press about the collapse of the Atlantic cod industry, and there is certainly disagreements between fishermen and scientists as to what is really going on out on the banks. What is true is that quotas are set very low for Atlantic cod and New England fishermen often find it difficult to avoid catching too much. Even when they fish on grounds to target other species, they are still finding more cod than is claimed by National Marine Fisheries Service.
Buying Cod

Codfish has been a valuable trade item since the early Middle Ages. This large, easy to catch fish is prized for its mild, flaky white flesh. The body of the fish lends itself to salting, making a foodstuff that is virtually imperishable, but is equally delicious served fresh. Cod, like a swimming swine is also amazingly versatile, nearly every part can be consumed. The head, including the meaty cheeks, the tongues, the swim bladder known as a sound, the liver, the roe, even the skin and bones have been traditionally consumed in some way.
You may even find that cod, even Atlantic cod is readily available at your local fish market. However much of this Atlantic cod is imported from Iceland and Norway. Meanwhile, domestic fishermen are harvesting the Atlantic cod at sustainable levels but still have to compete on the market with imports. If you care about the origin of your fish, ask your dealer for domestically caught cod.

Cod in the market may not be labeled “Atlantic cod” or “Pacific cod” but the differences in taste are very slight. Like all fresh fish, cod should not smell “fishy” when choosing a whole fish or fillets. Cod should not look dried out or off-colored and skinless fillets should look firm, not flimsy. If you are lucky enough to get it fresh caught, many old New Englanders will tell you it tastes better a day later.
If buying frozen cod fillets choose packages with bigger pieces with no signs of freezer-burn. The smaller portions can dry out faster sitting in cold storage, and can give an “off” taste. In recent years the packaging for frozen fish fillets has greatly improved and you can see it in the quality of the product. Don’t shy away from frozen seafood, it can often be better quality than what is available fresh.
Besides the Atlantic, Pacific, and Greenland Cod, there are several cod-like fish, like haddock, hake, and pollock, that can be used as substitutes. These fish are similar but have slightly different textures or a stronger taste. If fresh or frozen haddock is more available than cod, it makes an excellent alternative. I actually prefer haddock over cod.
Historic Recipe for Cod
Cod’s Head and Rice (1874 )
Take half a cod’s head and shoulders, and put in a saucepan with one quart of water to boil for fifteen minutes; fry, in four ounces of butter, one onion and two tomatoes, sliced, some chopped parsley, pepper, salt, and two cloves; when nicely fried, put it all into the saucepan, with the fish, add half a pound of rice, and boil until it is all well cooked; let it stand away from the fire for ten minutes, and serve up.
Source: From Head To Tale