Knowledge Title: Fishing under the ice

Other Title: fishing below ice

Knowledge Content:

    Cut ice in frozen waters and use a variety of fishing gear for fishing. It is common in lakes, rivers and reservoirs at high latitudes. Work should generally be carried out at fish clusters, no obstacles under water, and ice strength that can withstand the pressureof of workers and implements. The working hours coincide with the cold season, when fish are less active, so it facilitates fishing and storage. The Songhua River area of China has been fishing under the ice since more than 1000 years ago, and the mechanized study of under-ice large-line fishing has been carried out since the 1950s. The annual output of under-ice fishing in Northeast, North and Northwest China now accounts for a larger proportion. Net production can be up to 400 tons. The Soviet Union's under-ice fishing industry was more developed.

    Fishing gear mainly includes the following tools.

    Nets are mainly large pull-up nets under the ice. Sleeved single-bag net length is generally 500 to 1000 meters, some up to 2000 meters or more. The net height is generally about 1.5 times the bottom of the water to the undersurface surface of the ice. If the water is too deep, the floating and heavy net can be adjusted to make it in a suitable water layer. Fishing efficiency can be improved by the addition of underwater gillnets or foil spins.

    Drilling ice hole tools Handtools are ice-wearing, consisting of iron blades and wooden poles. Drilling ice machine has two kinds of mechanical transmission and hydraulic transmission, the former can be powered by the tractor to drive the drill pipe rotation and feed, the latter can be driven by the engineering dump truck hydraulic motor to drive the drill pipe rotation and feed. Drilling depth can be 80 to 170 cm, diameter up to 25 cm. The ice drill can also be mounted on a sled, towed forward by a tractor and powered.

    The main tools are rod-wearing and rod-walking hooks. The rod is generally 10 to 33 meters long and is made of bamboo rod or wooden strip with flat steel. The rod hook is an iron-headed wooden handle. The rope perforator can replace manual operation under ice and drive the large pull net forward through the guide rope. Among them are a small boat-like sealed housing with DC-driven propellers to drive underwater. The aircraft is equipped with a signal generator, the operator can hold the receiver to track on the ice. Whenever the roper travels about 100 meters, drill holes in the corresponding ice surface and pull out the waterline rope on its tail and winch the mesh. This type of rope perforator can not be controlled due to the direction of travel, tail tow with power cable, so the operation is not convenient. Another type of carrier guidance is a spindle-shaped closed container made of glass and steel, where operators can transmit carrier signals from a transmitter, manipulate the ropeper propeller to travel in a straight line, and correct the direction in a timely manner (Figure 1).

Fishing machinery consists of winch and starting machine. The winch is used for the winch network. The starting machine is used to winnet gear and is driven by the output shaft of a car or tractor.

    Fishing method first in the work field ice surface 800 to 2000 meters of the end of the line to cut 2 x 1.5 meters of the lower net and outlet, and then on both sides of the line to connect the net and outlet of the trolling network track each cut a series of ice holes about 25 cm in diameter, the distance between the adjacent two holes to pierce the pole or cable of a length to determine, Usually 30 to 100 meters. The towing line width is approximately 500 meters (maximum span must not exceed 80% of the total length of the mesh) (Figure 2). When working using traditional methods, the two rods are connected to the two ends of the large pull net by the waterline rope and wire rope respectively, and then the rod and the pull net are placed in the water under the ice through the lower net. With the help of a walking rod hook, the two poles each moved through the ice holes one by one along the scheduled trolling track. The wire rope is guided by a rod and, through the winch of the winch, drives the net to expand underwater and gradually sweeps across the water to fish, and the last two rods, together with the net, are winches from the net and the catch in the net is collected (Figure 3).