Drift netting is a fishing technique in which a net, called drift net , hangs vertically in the water column without anchored to the base. The net is stored vertically in the water by a buoy attached to the rope along the top of the net and a load attached to another rope along the bottom of the net. Drift drift generally depends on the loosely tied nature of the loops. Loose webs, like window curtains, grabbed the tail and fish fins and wrapped the fish in loose nets as he struggled to escape. However, the net can also function as a gill net if the fish is caught when the gills are caught in the net. Mesh size varies depending on the target fish. These nets typically target schools of pelagic fish.
Traditional safety net nets are made from organic materials, such as hemp, biodegradable. Prior to 1950, nets tended to have larger mesh sizes. Larger nets only catch bigger fish, allowing smaller, younger ones to get away. When drift net fishing grew on a scale during the 1950s, the industry turned into a synthetic material with a smaller mesh size. Synthetic webs are longer, odorless and may be barely visible in water, and do not break down. Most countries regulate floating net fisheries within their territory. Such fisheries are also often governed by international treaties.
Drift net fishing becomes a commercial fishing practice because it is cost effective. The net can be placed by a low-powered vessel making it fuel-efficient. The net nets are also effective for carrying large quantities of fish in one catch.
Prior to the 1960s the size of the net was unlimited, and the commercially produced net was generally 50 kilometers long (31 mi). In 1987 the US established the Driftnet Impact, Monitoring, Assessment, and Control Act limiting the length of the net used in American waters up to 1.5 nautical miles (~ 1.7 miles, ~ 2.778 km). In 1989, the General Assembly of the United Nations (UNGA) placed a moratorium on the practice of drifting fish. In 1992 the United Nations banned the use of drift nets longer than 2.5 km in international waters.
Video Drift netting
Kontroversi
Bycatch
Any fish that crosses the path of nets floating in the sea can get caught or caught in the net. Non-target individuals caught on the internet are called by-side catch. In 1994 the United Nations Food and Agriculture Organization (UNFAO) estimated that the global by-catch rate reached as high as 27 million tons of fish discharged by fisheries each year. Many individuals of non-target species perish as by-catching in a cast each deviation net. As a result, many species like this are now threatened with extinction. Species captured as by-catch include sharks, dolphins, whales, turtles, seabirds, and other marine mammals. Because nets are placed and can not be retrieved for days, mammals that breathe with air that becomes tangled in drown nets if they can not break free. In certain areas, the release of punitive measures for the unintentional arrest of marine mammals, as outlined by the Marine Mammal Protection Act, is extended to commercial deviation fishermen.
In the 1990s, floating net fisheries were responsible for 30,000 tons of sharks and rollerblading in a global catch each year. While filming National Geographic's Incidental Kill in the California Channel Islands where swordfish and sharks swim north, divers find that many net drift vessels have installed webs that night. A net a mile long each and nearly 100 feet (30 m) tall is placed to target swordfish and shoe thresher. They swam half of a net and in that length found 32 blue sharks dying in the net and 2 sharks hammer heads, sea lions, and manta rays all thrown back into the sea when the net was transported. in.
Although long-line fishing is a major contributor to seabird catch, seabirds are also trapped in significant drift nets. Studies conducted on 30 small-scale floating net fisheries in the Baltic Sea estimate that 90,000 sea birds die each year in the waves.
Bycatch is thrown back into the ocean either dead or with injuries that can result in death. If not eaten, dead animals decay, because bacteria use oxygen to break down organic matter. A large amount of matter that decomposes in the oceans causes the level of dissolved oxygen around it to decline.
Environmental damage
The webs are drifting away or abandoned in the sea by storms causing strong currents, accidental losses, or deliberate discharges into ghost webs. Synthetic webs are resistant to decay or damage, therefore ghost webs catch unlimited fish in the ocean. Sea animals are easily matted in a ghost net. The buoy line in the net allows to be driven in currents that cause ecological damage to plant life and substrate habitats as the nets are dragging the seafloor.
Illegal fishing
Most countries have jurisdiction over the waters within 200 nautical miles of their shores, called exclusive economic zones, established by the Law of the Sea. Outside these boundaries there are international waters, or loose seas. While fishing in international waters, ships must obey the rules of the country with which they fly, but there are no enforcers on the high seas. International waters make up 50% of the world's surface, but are the least protected habitats.
The decline in fish stocks has led to increased illegal fishing practices. Illegal, unregulated or unreported fishing between 11 and 26 million tonnes a year contributes one-quarter of the global catch. Illegal fishing includes taking small fish, fishing in enclosed waters, picking up more fish than allowed, or fishing during seasonal closures. Illegal fishing is particularly prominent due to lack of enforcement or punishment.
Although there are controls, breach of the net fisheries nets law is common. The Mediterranean Sea is the most overexploited. With 21 modern countries with coastline at sea, there are many fisheries harvesting a small area. When drift gear is prohibited, manufacturers modify the design of the net so that they no longer fall under the forbidden definition. The new definition was set in 2007 as "any gillnet held at sea level or at a certain distance below by a floating device, drifting with currents, either independently or with embedded boats." It may be equipped with a device aimed at stabilizing the net or to limit drift ".
Japanese fishing began to attract public attention in the mid-1980s when Japan and other Asian countries began sending a large fleet to the North Pacific Ocean to catch tuna and squid. Japan operates about 900 ships, generating about $ 300 million per year. The fishing vessels were blamed not only for the rough destruction of marine life, but also because of North Pacific salmon hunting, detrimental to the US and Canadian fisheries industry, and threatened fishing jobs that did not use such methods. The first Bush administration opposed the US driftnet ban for allegedly conflicts with an agreement with Japan and Canada regarding salmon fishing in the North Pacific.
Maps Drift netting
Other uses
The net webs are also used in ecological studies in studying downstream invertebrates and Ichthyoplankton. The nets are strung in the river and left overnight, collecting samples. This net is very important in understanding how the watershed functions. The quantitative estimates derived from the drift net used in this way in the river require careful consideration given the net clogging and decay in performance that can occur as a result.
See also
- Earthtrust
References
External links
- "Fisheries Business": documentary about illegal driftnet fisheries in the Mediterranean
- National Geographic's
Source of the article : Wikipedia
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