AS ordinarily used, the term fish includes, besides the fish proper, many other water animals, such as oysters, clams, lobsters, crawfish, crabs, shrimps, turtle and terrapin. In general fish contains the same kind of nutrients as other food materials, serving the two-fold purpose of tissue-building and the production of heat and energy. It is not so rich in nutrients or fuel value as meat, but furnishes an economical source of nitrogen and lends to the diet that variety which is almost essential.
There are, of course, dangers from eating fish, and though they are scarcely greater than dangers from other kinds of food, it may be well to consider some of them here.
Fish, like meat, may contain parasites injurious to man; but these are destroyed by thorough cooking.
Fish may also contain ptomaines. Their formation frequently accompanies putrefaction, and care should therefore be taken to serve fish only when it is in perfectly healthy condition. Fish which has been frozen and, after thawing, kept for a time before it is cooked, is especially likely to contain ptomaines.
Decomposition can often be recognized by the odor of the fish or by the test of laying the fish in water. Those which sink may be considered undecomposed and wholesome; those which float, unfit for use. The appearance of the fish is another guide: if the eyes have lost their sheen or the cornea is cloudy; if the gills are pale red or the scales dry or easily loosened, or if the meat is so soft that when pressed the indentation of the finger remains, it should be considered unfit for food.
Ordinarily the scales are removed and the fish drawn before it is delivered; but if not, this should be done at once. Then wash the fish thoroughly, wipe it dry. sprinkle with salt and put in a cold place. In the refrigerator fish will taint butter and other foods if placed in the same compartment, so that in most cases it is better to lay it on a plate on a pan of ice, setting the pan in the cellar. Fish that are frozen should soak in cold water until they are thawed, but should not be allowed to remain until they are flexible. Salt fish should be soaked in fresh water, skin side up, to draw out the salt.
To remove the scales hold the fish by the tail and scrape firmly toward the head with a small sharp knife, held with the blade slanting toward the tail. Scrape slowly so that the scales will not fly, and rinse the knife frequently in cold water.
If the fish is to be served whole, leave the head and tail on and trim the fins; otherwise remove them.
To open small fish make an incision under the gills and squeeze out the contents by pressing upward from the middle with the thumb and finger. To open large fish split them from the gills half way down the body toward the tail; remove the entrails and scrape and clean, opening far enough to remove all the blood from the backbone, and wiping the inside thoroughly with a cloth wrung out of cold, salted water.
To skin a fish remove the fins along the back and cut off a narrow strip of the skin the entire length of the back. Then slip the knife under the skin that lies over the bony part of the gills and work slowly toward the tail. Do the same with the other side.
To bone a fish clean it first and remove the head. Then, beginning at the tail, run a sharp knife under the flesh close to the bone, scraping the flesh away clean from the bone. Work up one side toward the head; then repeat the same process on the other side of the bone. Lift the bone carefully and pull out any small bones that may be left in the flesh.