Drift nets are sea smooth nets, 15 to 75 m long and 10-15 m high, connected (tied up) in one order of 100-150 pieces ' attached to one rope. Driftnets are so called because a vessel with an order of nets lowered into the water drifts, carried away by the force of the current and the wind. When drifting, the driftnet covers a large fishing area. The order of nets is lowered to different depths. Depending on the horizon of the fish, driftnets are used to catch herring, cod and Pacific salmon. Nowadays, driftnet fishing is becoming a thing of the past because of the high cost of manual labor.
Drift nets are usually based on the entanglement properties of a loose net. The folds of the loose net cling to the fish's tail and fins and wrap it into the loose net when it tries to escape. However, nets can also function as gill nets if a fish is trapped when its gills get stuck in the net. The size of the net varies depending on the fish being targeted. These nets usually target schools of pelagic fish.
Traditionally, driftnets were made from organic materials such as hemp, which are biodegradable. Before 1950, nets tended to have a larger mesh size. A larger net only caught larger fish, allowing smaller and younger fish to slip through. When driftnet fishing increased in the 1950s, the industry switched to synthetic materials with smaller mesh sizes. Synthetic nets last longer, are odorless, can be nearly invisible in the water, and do not biodegrade. Most countries regulate driftnet fisheries in their territories. Such fisheries are also often regulated by international agreements.
Drift nets are also used in ecological studies when studying downstream drift of invertebrates and ichthyoplankton. Nets are stretched across the stream and left overnight to collect samples.
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