General Facts About Fisheries
Fisheries involve the capture or harvest, and also the processing, for profit, of sea, coastal, and inland aquatic animals and plants to be used for human food, animal food, or industrial products. In contrast, sport fishing is the capture of fish and shellfish for recreation and enjoyment.
In a world in which the arable land areas have been almost fully explored, the food potential of the seas is attracting increased attention. The increase of world population has given new importance to this last of the unexplored food sources.
A square mile of sea produces an average of 13,000 tons of vegetation annually; the world total is probably five times that of vegetation on land. Sea plants for the most part are microscopic and serve mainly as food for small animals, such as copepods, upon which fish feed, but sea plants are recognized as potential food for men and domestic animals. Varieties, conditions under which they grow best, their nutritional value, methods for cultivating and harvesting them—all are things that have to be learned.
The principal commercially valuable fauna of the sea and inland waters are fish, shellfish, and mammals. Fish have always been the most important of all the living resources of the sea.
Types of fish include the teleostean, or bony, fish such as herring, tuna, salmon, flounder, and cod; ganoids, or hard-scale fish, such as sturgeon, garfish, and paddlefish; and elasmobranchs with lamellate gills, such as sharks, skates, and rays. Fish are more abundant than marine mammals (whales, porpoises, walruses, sea otter, sea lions, and seals). They are also more widely distributed and less elusive. In most parts of the world an average fisherman with an average vessel and gear catches a few tons of fish in a day's effort. Fish are also easier to prepare, preserve, and market than mammals.
Although fish are plentiful and easily caught, more than 90% of the mass of animal life in the sea is composed of invertebrates, more commonly known as "shellfish." The shellfish are divided into two major groups: (1) crustaceans, usually distinguished by a chitinous covering, such as shrimp, crabs, and lobsters; and (2) mollusks, commonly with a calcareous shell, such as oysters, clams, scallops, squid, and octopus. There are a great variety of genera and species of shellfish. Some species occur in immense numbers, but few are known or usable by humans because of the limitations of his information at present.
The principal food shellfish are oysters, clams, scallops, lobsters, shrimp, and squid. Although these are the best known at present, the potential exists for finding and using others. Some fish and shellfish species that are not now commercially desirable are discarded at sea when North Atlantic fishermen hunt for cod and haddock. Shoals of sardinelike fish have been found by exploratory fishing in the Gulf of Mexico, yet no one seeks them commercially. Many kinds of marine invertebrates, all rich in nutrients, are not being harvested, even though they are close to areas where people are in need of protein food. Fishermen take enough odd species from time to time to realize that nets, hooks, and other gear miss innumerable fish.
Other Marine Animals
Aquatic or marine mammals, such as whales, dolphins, seals, sea lions, walruses, and sea otter, include a larger proportion of species that are commercially useful than is found among any other group of animals in the sea. Although some of the marine mammals are very valuable, their usefulness is severely limited by the smallness of their populations and by a low rate of reproduction.
Of lesser importance are other aquatic fauna including reptiles, such as turtles; amphibians, such as frogs; echinoderms, such as starfish and sea urchins; and tunicates, such as sea squirts. Also included among the products of the sea are aquatic animal residuals, such as pearls, mother-of-pearl, sponges, and coral.
One of the most significant events in humanity's thinking about conservation since the mid-19th century has been the change from "preserve" to "conserve." Those who first became alarmed about the rapid dissipation and destruction of natural resources turned to "preserve." That concept meant reserving for future needs, a saving for the future by nonuse in the present. This is possible only with nonrenewable resources—such as coal, oil, and minerals. If these resources are not taken, they remain unchanged. But it is impossible to store or preserve renewable crops such as fish, shellfish, wildlife, timber, and, in most instances, water. Aquatic fauna or flora must be harvested each season because the surplus will die in one way or another. To use is to conserve—and that is the keystone of conservation of resources of aquatic fauna or flora.