There are essentially two types of trap, a permanent or semi-permanent structure placed in a river or tidal area and pot-traps that are baited to attract prey and periodically lifted. Artisanal techniques Dam fishing - An artisanal technique called dam fishing is used by the Baka pygmies.
This involves the construction of a temporary dam resulting in a drop in the water levels downstream—allowing fish to be easily collected.
They are shown in medieval illustrations and surviving examples have been found. Basket weirs are about 2 m long and comprise two wicker cones, one inside the other—easy to get into and hard to get out. Such fish traps were evidently controversial in medieval England. The Magna Carta includes a clause requiring that they be removed: A wheel complete with baskets and paddles is attached to a floating dock.
The wheel rotates due to the current of the stream. The baskets on the wheel capture fish travelling upstream and transfer them into a holding tank. When the holding tank is full, the fish are removed. Lobster traps - also called lobster pots, are traps used to catch lobsters. They resemble fish traps, yet are usually smaller and consist of several sections.
Lobster traps are also used to catch other crustaceans , such as crabs and crayfish. They can be constructed in various shapes, but the design strategy is to make the entry into the trap much easier than exit.
The pots are baited and lowered into the water and checked frequently. Historically lobster pots were constructed with wood or metal.
Today most traps are made from checkered wire and mesh. It is common for the trap to be weighted down with bricks. A bait bag is hung in the middle of the trap. In theory the lobster walks up the mesh and then falls into the wire trap. Bait varies from captain to captain but it is common to use herring.
In commercial lobstering five to ten of these traps will be connected with line. A buoy marks each end of the string of pots. Two buoys are important to make retrieval easier and so captains don't set their traps over each other. Each buoy is painted differently so the various captains can identify their traps. Animals[ edit ] Chinese man with fishing cormorant.
Cooperative human-dolphin fisheries date back to the ancient Roman author and natural philosopher Pliny the Elder. In Laguna, men stand in shallow waters of the lagoon, or sit in canoes, forming a line, and waiting for the dolphins to appear. One or more resident dolphins drives fish towards the waiting fishermen. Then at a critical moment when the dolphins are close enough to the fishermen, one dolphin emerges from the water for an average duration of 1.
This sequence serves as a signal to the fishermen to cast their throw nets. The dolphins then feed off the fish that manage to escape the nets. Likewise, studies show that fishermen casting their nets following the unique signal catch more fish than when fishing alone, without the involvement of the dolphins.
Fishermen use the natural fish-hunting instincts of the cormorants to catch fish, but a metal ring placed round the bird's neck prevents large, valuable fish from being swallowed. The fish are instead collected by the fisherman. Portuguese Water Dogs - Dating from the 16th century in Portugal, Portuguese Water Dogs were used by fishermen to send messages between boats, to retrieve fish and articles from the water, and to guard the fishing boats.
Labrador Retrievers have been used by fishermen to assist in bringing nets to shore; the dog would grab the floating corks on the ends of the nets and pull them to shore. Remora fishing - The practice of tethering a remora , a sucking fish, to a fishing line and using the remora to capture sea turtles probably originated in the Indian Ocean.
The earliest surviving records of the practice are Peter Martyr d'Anghera's accounts of the second voyage of Columbus to the New World Scientists carrying out a population and species survey using electrofishing equipment Christ catches fish using a miracle technique Artisanal techniques Basnig - a traditional method of fishing in the Philippines that combines the use of bag nets and attracting fish with high-powered lamps. Specialized outrigger boats known as basnigan are used.
Electrofishing - is another recently developed technique, primarily used in freshwater by fisheries scientists. Electrofishing uses electricity to stun fish so they can be caught. It is commonly used in scientific surveys, sampling fish populations for abundance, density, and species composition.
When performed correctly, electrofishing results in no permanent harm to fish, which return to their natural state a few minutes after being stunned.
Fish aggregating devices - are man-made objects used to attract pelagic fish such as marlin , tuna and mahi-mahi dolphin fish. They usually consist of buoys or floats tethered to the ocean floor with concrete blocks. Dredging - There are types of dredges used for collecting scallops , oysters or sea cucumbers from the seabed. They have the form of a scoop made of chain mesh and they are towed by a fishing boat.
Dredging can be destructive to the seabed, because the marine life is unable to survive the weight of the dredge. It is extremely detrimental to coral beds since they take centuries to rebuild themselves. Unmonitored dredging can be compared to unmonitored forest clearing, where it can wipe out ecosystems. Nowadays, this method of fishing is often replaced by mariculture or by scuba diving.
Fish finders - are electronic sonar devices which indicate the presence of fish and fish schools. They are widely used by recreational fishermen. Commercially, they are used with other electronic locating and positioning devices. Fishing light attractors - use lights attached above or underwater to some structure to attract fish and bait fish. Fishing light attractor are operated every night. After a while, fish discover the increased concentration of bait surrounding the light.
Once located, the fish return regularly, and can be harvested. Flossing - Harvesting machines - have recently been developed for commercial fishing. Harvesting machines use pumps to pump fish out of the sea. Dredges have also been mechanized so that they directly transfer mollusks to the surface as are dredged. Payaos - a type of fish aggregating device used in Southeast Asia , particularly in the Philippines. Payaos were traditionally bamboo rafts for handline fishing before World War II, but modern steel payaos use fish lights and fish location sonar to increase yields.
While payaos fishing is sustainable on a small scale, the large scale, modern applications have been linked to adverse impacts on fish stocks. A laksegiljer in Osterfjord, Norway Shrimp baiting - is a method used by recreational fisherman for of catching shrimp. It uses a cast net , bait and long poles. The poles are used to mark a specific location and then bait is thrown in the water near the pole. After several minutes the cast net is thrown as close to the bait as possible and shrimp are caught in the net.
In the s the sport became popular in the south eastern coastal states of the USA. Laksegiljer- small cabins standing on stilts where a fisherman sits. This method of fishing entails a net where the opening is controlled by a line tied to a rock.
Under the cabin on the seabed is a white plank. When a salmon swim across the plank, the fisherman sees it and throws the rock into the water so the line closes the opening of the net, trapping the salmon. In Norway this method of fishing is banned, but in Osterfjord locals can obtain a special permit to use this method in order to maintain the old traditions.
Destructive techniques[ edit ] Destructive fishing practices are practices that easily result in irreversible damage to aquatic habitats and ecosystems. Many fishing techniques can be destructive if used inappropriately, but some practices are particularly likely to result in irreversible damage.
These practices are mostly, though not always, illegal. Where they are illegal, they are often inadequately enforced. Blast fishing Dynamite or blast fishing is done easily and cheaply with dynamite or homemade bombs made from locally available materials. Fish are killed by the shock from the blast and are then skimmed from the surface or collected from the bottom.
The explosions indiscriminately kill large numbers of fish and other marine organisms in the vicinity and can damage or destroy the physical environment. Explosions are particularly harmful to coral reefs. Bottom trawling Bottom trawling is trawling towing a trawl, which is a fishing net along the sea floor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling.
Benthic trawling is towing a net at the very bottom of the ocean and demersal trawling is towing a net just above the benthic zone. Bottom trawling targets both bottom-living fish groundfish and semi-pelagic species such as cod , squid , shrimp , and rockfish. Bottom fishing has operated for over a century on heavily fished grounds such as the North Sea and Grand Banks.
While overfishing has long been recognised as causing major ecological changes to the fish community on the Grand Banks, concern has been raised more recently about the damage which benthic trawling inflicts upon seabed communities. This species is home to a diverse community of deep sea organisms, but is easily damaged by fishing gear. On 17 November , the United Nations General Assembly urged nations to consider temporary bans on high seas bottom trawling.
Cyanide fishing Cyanide fishing is a method of collecting live fish mainly for use in aquariums , which involves spraying a sodium cyanide mixture into the desired fish's habitat in order to stun the fish. The practice hurts not only the target population, but also many other marine organisms, including coral and thus coral reefs. With such high mortality numbers, a greater number of fish must be caught in order to offset post catch death.
Muroami Muroami is a destructive artisan fishing method employed on coral reefs in Southeast Asia. An encircling net is used with pounding devices, such as large stones fitted on ropes that are pounded onto the coral reefs.