Method for estimating form of middle-layer trawl netting gear in operation process

Abstract

The invention provides a method for estimating form of a middle-layer trawl netting gear in the operation process, which comprises the following steps of: assuming that a middle-layer trawl is an elliptical cone in the operation process, establishing an equation and acquired network port height data, and determining the shape of a network port during dragging; solving an equation according to thetrawl horizontal (long axis) cross section structure and the netting gear parameters, and obtaining the distances from the long axis and net opening center point of the net sleeve horizontal expansion and net body net bag connection position to the net sleeve horizontal expansion center point; determining the shape of the net opening, the shape of the joint of the net body and the net bag and thelength of the net sleeve and net body assembling force line to obtain the partial shape of the trawl net body; establishing an equation to solve upper and lower outline shapes; after the length of the net bag force line is determined, acquiring the shape of the net bag by combining the ellipse of the cross section of the net body net bag joint. According to the estimation result, the operation condition of the netting gear can be known during operation, accidents are avoided, fishing operation is adjusted, and fishing success rate is increased.

Description

technical field [0001] The invention relates to the field of research on the hydrodynamic performance of fishing gear, in particular to a method for estimating the shape of a mid-level trawl net during operation. Background technique [0002] As the most extensive and efficient fishing technology in marine fisheries, trawling accounts for more than 40% of the world's total fishing output. Trawling is a fishing method in which a fishing boat drags a bag-shaped net to force the target to enter the net. Trawl nets interact with hydrodynamic forces during dragging, resulting in morphological changes in the net gear. The shape of trawl gear can reflect the stress state of the trawl net and the selection mechanism of fishing objects. The study of related shape will play a positive role in improving fishing efficiency and achieving balanced fishing. [0003] my country began to carry out pelagic trawling fishery in the 1980s. Due to the huge scale of trawl nets, the operating wat...

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Problems solved by technology

[0003] my country began to carry out pelagic trawling fishery in the 1980s. Due to the huge scale of trawl nets, the operating water layer extends from the sea surface to thousands of meters underwater, and it is difficult to monitor the shape of net gear, which requires a lot of personnel and financial resources. Therefore, the research progress on trawl shape slow

With the development of fishing equipment and the use of net position meters, the effective observation of the shape of the trawl net opening has been realized on commercial fishing boats, but the overall shape of the trawl net is difficult to effectively monitor

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