Trawling

Trawling refers to fishing with nets that are pulled ( towed ) behind a ship. Trawls are the most important fishing equipment deep sea fishing.

Trawls

A trawl is a one or more trawlers nachgeschlepptes network, which is used to catch schooling fish or bottom fishing. Today, mainly two types of trawls are used:

• The pelagic trawl or floating trawl
• And the bottom trawl or trawl.

General information on construction

A trawl is a net that is pulled by one or more vessels through the water. It is reminiscent of a horizontal bag which is narrower at the rear. It has a very wide opening. This is produced by the cultivation of skilled located on the lower side weights, and on the upper side lying floats.

The mesh size of the net is completely tailored to the type of fish to be caught. However, the stitches are at the opening always greater than at the end of the network, the so-called " cod-end ".

• See also: Schetel

Pelagic trawls

Pelagic trawls are designed to catch fish species that live in the open water, for example, all round fish such as snapper, cod, pollock and mackerel, herring, sprats, anchovies and sardines also to a lesser extent.

A pelagic trawl is funnel-shaped and end up running into a pocket, the cod-end, in which the fish are collected. The opening of the net is 50-70 m high and 80-120 m wide, the total length of the network is usually 1500 m. The nets are towed at a speed of 3-4 knots ( about 5 km / h) in a water depth of 50 to 300 m, sometimes up to 600 m, from one or two trawlers ( pair trawling ). The location of the fish is done when fishing with pelagic trawls usually by sonar and echo sounder.

Trawls

Trawls are fishing for demersal fish such as plaice, sole, dab ( flatfish ), and crustaceans such as shrimp that live on the ocean floor. Bottom trawls are used in water depths of 100-1500 m. In the Wadden Sea to the North Sea and on the Baltic coast nets of fishing trawlers to be used in so-called beam trawls.

Also, the bottom trawl is a funnel -shaped and has at the end of a collection bag for the fish, but generally much shorter than the pelagic net. On the bottom of the power input is a weighted footrope that is dragged along the ocean floor and the fish should startle. Modern Bottom trawls also have lateral shear planks of wood or steel, through which a larger area of ​​the sea floor is plowed. Bottom trawling can deep-sea organisms, for example, threaten the fauna of seamounts.

Area of ​​application

Trawls are used primarily in the North Atlantic. The leading trawling nations are in this case France, Ireland, Iceland, the Netherlands, England, Denmark and Spain. Among other things, the types of fish tuna, perch, herring, mackerel, horse mackerel and anchovies are caught. Trawls are also used in the Baltic and North Sea to fish for the North and Baltic shrimp ( " shrimp ").

In June 2008, agreed the 15 states of the Oslo - Paris Convention OSPAR that in an alpine deep-sea submarine mountain range called the Mid-Atlantic Ridge severely limited deep-sea fishing with trawls, is also forbidden in some areas. The resulting reserve is located halfway between Iceland and the Azores, is about the size of Italy and is one of the largest marine protected areas in the world.

Criticism of the trawling

Several environmental organizations are very much against bottom trawling, because in this method of fishing of the seabed and the subsequent living beings are destroyed. According to the British science magazine New Scientist (No. 2410, p 6) are likely to be destroyed even as yet unknown and undiscovered species and greatly reduced biodiversity.

Another of the trawling practiced criticism is the high proportion of bycatch (80-90%), resulting from the use of trawl nets. This includes both juveniles as well as other (fish ) species and Cetacea (whales and dolphins) who are drowning in the nets. With new networks and selective fishing fishermen could largely avoid the unwanted by-catch.

A disadvantage of trawling is the diminished quality of the catch. While other methods of fishing, such as long lines, the fish are fresh from the water, they die in the trawl nets already in the water by the pressure of other fish in the net, and are then pulled through the water dead.

The ban bottom trawling is a major goal of Greenpeace.

In 2004, a petition against the bottom trawl fishing was released, which was signed by 1100 scientists.

The end of 2006 had eleven nations bottom trawl fishing fleets, with Spain has the most ships with this equipment. The attempt to reach agreement at the United Nations in 2006 about a ban, was torpedoed by Iceland in particular.

2011 launched the campaign network Avaaz.org on to an action against the basic networks. The occasion was a meeting of UN decision-makers on September 15, 2011. Many fisheries biologists demanding an end to deep-sea fishing, because in their opinion, destroy industrial fishing methods, the largest ecosystem of the oceans. This requirement is supported by the Deep Sea Conservation Coalition.