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Trawling Structure And Fishing Principle
Mar 17, 2018

Trawl structure:

Trawling can be divided into two forms of sleeved trawls and sleeveless trawls according to structural features. A sleeved trawl generally has 1 net sac and 2 net sleeves, and the nets have upper and lower tiers that are respectively equipped with an appropriate number of floats and sinkers so that the net openings are opened vertically. It is the main structural form of marine trawls and is also used in inland waters, but on a smaller scale. The sleeveless trawl structure has two types: sleeveless single-sleeve type and sleeveless multi-bag type.

1. Sleeveless single-bag trawl:

It is a small trawl, and the net mouth is generally equipped with a fixed support device to keep the mouth open, and it is used both in the ocean and inland waters. Sleeveless, multi-bag trawls generally have more than two sac. The number of net sacs depends mainly on the ecological habits of the fishing targets and the tonnage of the fishing vessels. The horizontal and vertical opening of the net opening is ensured by means of the trawl spacing and vertical struts of the two ships.

2. With sleeves and sleeveless trawl:

It is generally used in the bottom waters, and the middle trawls are mainly used in middle waters. The difference between it and the bottom trawl is that there is usually no net sleeve or a short net sleeve, which can reduce the resistance of the net and increase the drag speed; the net mouth is a square or rectangle; the net equipment is equipped with a sinker It is also equipped with a hammer and other settlement devices to expand the vertical opening dimensions of the net and maintain the position of the net in the water layer.


Trawling fishing principle:

Trawling is the use of the ship's movements to tow fishing gear in the sea or in the sea to advance, forcing fishing gear through the waters of fish, shrimp, crabs and other fishing objects into the nets to achieve the purpose of fishing.

When the fishing vessel is towing the net, the net plate will generate expansion force under the action of the water flow, which will allow the net to open horizontally. During operation, the fishing boat moves forward slowly and releases the gear from the tailslide, connecting the stencil to the traction and disengaging it from the two slats. Then the fishing boat quickly advanced and gradually released two whirlpools. After the truncated stream has been released for a predetermined length, the fishing boat advances by a predetermined drag and dragging speed. The length of the dragline is generally 3 to 5 times the water depth. The trawl speed is generally 3 to 5 nautical miles per hour. Every 3 hours or so from the network once. When the net is lifted, the fishing boat advances in a progressively slow manner and in turn gathers kinks. When twisted to the stencil, the stencil is fixed on the stencil frame, so that it is detached from the traction, and the net is continued to be retracted. Drag onto the deck and take out the catch.


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