Fish may be captured with spear, trap, line or net. Which of these methods is employed necessarily depends very much upon the size and habits of the fish, and upon the skill and available equipment of the fishermen. Spears and traps were used in prehistoric times and survive to this day in various forms, e.g. harpoons, lobster pots, hedge baulks, fishing weirs and the various ingenious traps and entanglements that are used by primitive races in all parts of the world. The logical development of the spear and the trap into the line and the net was made possible by the invention of string. To design and construct a trap, it is generally necessary to know something of the habits of the fish to be caught. Hedge-baulks and fishing weirs are fairly extensive enclosures made of brushwood, basket work, stakes or stones, constructed on the foreshore in such a way that at high tide the sea carries the fish into the enclosure and leaves them there when it recedes. These fishing weirs are probably the primitive origin of most forms of fishing nets. The crab or lobster pot or creel is constructed of basket-work, in shape somewhat like a safety inkpot, so that the lobster or crab can easily enter it, but, once in, is unable to escape. Lobster pots, suitably baited with fish and weighted, are distributed over the fishing ground—a rocky bottom full of crevices—from small, open boats, and are gathered the next day. Fishing with hook and line is also a very ancient method. Before the discovery of metals, the hooks were made of bone. Some people—notably the Chinese—frequently use unbaited hooks, and rely upon the jerk of the hook at the right moment to secure the fish. Generally, however, the hook is suitably baited, the method being used chiefly for fish that seek their food by scent or sight, e.g. cod and shark. Line fishing for cod is still employed on a large scale off the North of Scotland and the coast of Newfoundland. In lining, the fish are caught individually. A “line” may be as much as seven miles long. Short pieces of line from two to three feet long are attached to it at regular intervals. These lines are called the “snoods,” and carry the hooks. The line is usually shot at night, and fished in the morning. In most cases line fishing is rapidly being superseded by trawling. The invention of netting marked a notable advance in the primitive development of the fishing industry. The net in all its various forms and applications is the characteristic and all-important implement of the fishing industry. A net may be used either to surround a fish and drag it out of the water, as in seining or trawling, or it may be used to enmesh the fish, as in drift netting. The rise and development of the sea fishing industry has been due very largely to the gradually improved efficiency of the net.