Fish and Shellfish represent the largest stock of "wild" food on the planet, as well as the growing proportion of this food which is "farmed." Consumption of fish appears to date back to extremely early times, evident through empty sea shells found by archaeologists at prehistoric sites. Not only do early Chinese writers and classical Greek authors exhibit a sophisticated range of fishing techniques in their writings, they also show considerable discrimination between the species. The techniques in catching fish have changed relatively little over the centuries, as fisherman still rely on the spear, the line and hook, and the net.
The nutritional and medicinal qualities of fish have been recognized in parts of the world for over 4,000 years. Not only are they high in protein, but since the weight of fish is supported by water, they have a less elaborate skeleton and therefore provide more flesh in relation to meat in comparison to land animals.
Humanitarian considerations over fish and shellfish generally exists in regards to a few selective sea creatures, but even a number of vegetarians will include fish in their diet. Marine mammals such as dolphins, however, are now considered almost sacred by all but the Eskimos, and there is growing concern over how to kill lobsters and crabs painlessly.
The number of edible species of fish are so plentiful, especially in warm water, that its likely no one will ever taste them all. Even Norwegians and Singaporeans, who head the league table in per capita consumption, can only expect to sample the range. There also lies confusion in that the same fish may carry a range of different names, even within one language, such as Italy's common gray mullet, which has over 40 different names. Most fish, though, fall into the general categories of either round fish or flatfish.
Round fish have thicker bodies and many of their bones are attached to their finds. They can be filleted or cut into steaks, but both will contain small pin bones. Flatfish have a flat central bone with a row of bones attached on either side, making them easy to filet, but hard to cut into steaks.
When shopping for fish, the product should look as much as possible as if it is still swimming in the sea, with shining bright flesh, gills deep pink to red, and eyes protruding and glossy, never sunken and cloudy. The flesh should be slippery and firm, leaving no indentation when pressed with a finger. It should smell of the sea, but the smell should never be "fishy" or strong. The exception being skate fish, which can smell very faintly of ammonia. Fish fillets should have flesh that looks translucent and succulent with no sign of discoloration. Fish deteriorates more quickly once it has been cooked. Buying and storing shellfish varies from type to type because it is all so different from one another.
Fish, if possible, should be kept close to 32 degrees Fahrenheit for best storage. If put in a warmer home refrigerator, one should bury their fish in ice or surround with ice packs, if possible. Fish is best when used on the day it is purchased, and should never be kept for much longer than a week if not frozen.
When cleaning fish, one should remove any fins with a pair of heavy scissors, scale the fish by running the back of a knife from the tail toward the head, and cutting along the belly from under the gills to the anal opening to remove the innards. The inedible gills should then be removed and discarded using the same opening used to remove the innards. The fish is then ready to be cut up into steaks or fillets, or the head or tail can be removed if necessary if serving the fish whole. Scraps including the head, tale, fins, and bones should then be saved for the stockpot.
Techniques for cooking fish remain similar around the world, with decisions on grilling, poaching, steaming, pan-frying, deep-frying, stewing, and braising often relying on the size, shape, and fat content of the fish. There are also categories of fish dishes which are generically although not always specifically transferable around the world. Contrasts do lie in some areas like ingredients, as fish coated in an English batter and fried in beef dripping is very different from the same fish fried in a wok in peanut oil, or fish simmered in a court bouillon flavored with Mediterranean herbs and the same fish cooked in coconut cream with lemon grass and other South East Asian flavorings.
The fat content of fish is an important consideration in deciding how to cook it. Lean fish can dry out at high temperatures, so a protective coating can keep it moist when frying, while marinating or basting them can aid when broiling them. Lean and moderately lean fish are best cooked with moist methods like steaming, poaching, or baking in a sauce. Oily fish almost baste themselves during cooking, and are ideal for broiling, grilling, or pan-frying.
When calculating the cooking time of fish, it is recommended that a cook use the "Canadian method" of basing the time on the maximum thickness of the fish. It is important to remember, however, than the time it takes heat to penetrate an object is not in simple proportion to its thickness, but to the square of the thickness. This also explains the importance of scoring the sides of a fish, which if done properly at the correct intervals, and deeply enough, can halve the maximum distance which the heat much travel to reach the innermost park, thereby reducing the cooking time to a quarter of what it would have been.
There are also those that would argue that fish even need to be cooked at all, such as Japan with their Sashimi, and the Ceviche of Latin America. Japan's sashimi requires really fresh seafood, presented with Japanese artistry, while ceviche uses a marinade of lemon or lime juices to cause the denaturation of protein in the meat in much the same way that the heat in conventional cooking would do. Thanks to the growing love of sashimi around the world, fish markets most everywhere are carrying higher quality product.
Seafood is occasionally poached in a Fish Kettle, which have a long and narrow shape to match the shape of a normal fish, with a removable grid that permits the poached fish to be lifted out without damage. There are almost always made of aluminum these days, though examples of tinned copper survive. Some antique fish kettles are relatively wider, presumably to poach multiple fish at once, though flatfish such as Turbot would not fit into even a wide oblong kettle, so there is a lonzenge-shaped variety called Turbotiere in French which is made special for them.
Overcooking fish drains moisture and flavor from the meat, and texture can be destroyed. To check if a fish is cooked, gently pull back the flesh with a knife and look for it to be opaque all the way through, flaking easily. With filleted fish, the appearance of soft white drippings is a sign that it is cooked.
Small whole fish fermented in vats of brine help make the fish sauce essential to the diets of South East Asia. The product, closely related to Garum and Liquamen of Classical Greece and Rome, are high in protein, and have a composition that resembles soy sauce.
The general selection of fish varieties, as mentioned above, is so vast that one could likely never eat all of them. The most common broad categories of Lean Fish are Cod, Flounder, Grouper, Haddock, Halibut, Mahimahi, Perch, Red Snapper, Rockfish, Sea Bass, and Sole, while the Moderately Lean Fish include Catfish, Orange Roughy, Porgy, Sea Trout, Swordfish, Trout, and Tuna, and the Moderately Oily and Oily Fish include Bluefish, Carp, Mackerel, Pompano, Salmon, and Whitefish. Not quite as vast a category, shellfish refers to any animal living in water whose outer cover is a shell, whether testaceous, as an oyster, or crustaceous, as a crab. Other types of shellfish include Shrimp, Lobster, Clam, Mussel, Scallop, Abalone, Squid, Cuttlefish, Octopus, and Sea Urchin.
References:
Oxford Companion to Food; 1999; Pages 301 - 304, 717
The Cooking Enthusiast; 2000 ; Page 117
Encyclopedia of Cooking Skills & Techniques; 1999; Pages 64 - 67
Joy of Cooking; 1997; Pages 488 - 489, 527 - 529
How to Cook Everything; 1998; 275 - 276