Self-submergence frame type sampling method of marine juvenile fish by sampling net

Abstract

The invention discloses a self-submergence frame type sampling method of marine juvenile fish by a sampling net, which relates to a sampling method of marine juvenile fish and needs to provide a net tool for sampling the marine juvenile fish away from the bottom and a method for controlling sampling depth. The sampling net tool provided for the sampling method is characterized in that a net port of the sampling net tool is welded into a rectangular frame by a steel pipe; four non-section net pieces with meshes of 10mm are cut into trapezoidal net pieces which are wound into shapes of a net bag; a wide port of the net bag is engaged with the rectangular frame; a narrow port of the net bag forms a bag net; the tension length of netting of the net bag is 4 meters; the lower edge of the net port is connected with a submergence device which is made into a framework by the steel pipe; a submergence deflector covers the upwind surface of the framework of the submergence device; both ends of the submergence device are hinged with triangular drawing plates which are connected with a cross rope; upper transverse beams of the net port are all uniformly tied with floaters; ship speed is between 3 knots to 3.5 knots during net placement; and the length of the cross rope is controlled and released gently by operating water depth so that the net tool is placed on an operating water layer to draw the net and sample. The sampling method is suitable for sampling the marine juvenile fish.

Description

technical field [0001] The invention relates to a sampling net for juvenile marine fish and a sampling method thereof. technical background [0002] At present, in the investigation of marine fishery resources, mid-level trawls are often used to catch marine off-bottom fish to obtain data on samples and quantities, and plankton nets are used to collect plankton samples. However, the middle layer trawl is huge, heavy, heavy lifting workload, and inconvenient to operate. On the other hand, the mesh of the mid-level trawl is relatively large (the minimum mesh of the capsule net is generally above 50mm), and juvenile fish in the ocean can easily escape from the mesh, making it difficult to obtain samples of juvenile fish. Although the plankton sampling net has a relatively dense mesh, the net opening is very small and cannot be dragged horizontally, but can only be dragged upward for sampling. Due to the influence of water flow, it is difficult to control the depth of the sampl...

AI Technical Summary

Problems solved by technology

However, the middle layer trawl is huge, heavy, heavy lifting workload, and inconvenient to operate

On the other hand, the mesh of the mid-level trawl net is relatively large (the minimum mesh of the capsule net is generally above 50 mm), and juvenile fish in the ocean are easy to escape from the mesh, and it is difficult to obtain samples of juvenile fish

Although the plankton sampling net has a denser mesh, the net opening is very small and cannot be dragged horizontally, but can only be dragged upward for sampling. Due to the influence of water flow, it is difficult to control the depth of the sampling water layer, which is not suitable for sampling juvenile fish.

In addition, during the investigation of marine fishery resources, vertical fish finders are used to detect marine organisms in seawater, but the monitor can only display the ultrasonic echoes of a creature or object in a certain water layer, and cannot distinguish what kind of creature it is. An easy-to-operate sampling net is needed to quickly reach the desired water layer to capture biological samples to determine species and density

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