At present, the production of prawns from trawling trawls has become one of the important methods of marine fishing in coastal fishing areas, and its production value has increased year by year throughout the entire marine fishery production value. Because this operation method is a single-bottomed mast trawl operation, the technical design of the net equipment design, assembly, operation adjustment and fishery selection are all relatively strong. Therefore, slight negligence will affect the production of shrimp. In particular, the adjustment technology in the raft trawl operation is the key to the fishing production technology. For example, in the production practice, we often encounter this phenomenon: similar horsepower fishing boats, the use of the same specifications of the net equipment, production in the same fishery, but the net output The difference is very wide, with the highest of nearly 1,000 pounds, and the lowest is only 10 pounds or even empty. The reason for this is closely related to the correct application and adjustment of fishing gear and fishing methods. Therefore, we constantly sum up experience to improve fishing techniques, improve the effectiveness of raft trawl fishing, and overcome past imbalances in production. Now we will introduce the adjustment technology and production experience of the trawl fishing tackle fishing nets as follows: I. Selection of gear specifications and adjustment of gears Due to the sloping trawls, shrimps with low inhabited water layer and weak swimming capacity are caught, and crabs and clams are caught. As a result of waiting for fish, it has the characteristics of active and flexible, actively chasing shrimp and adapting to a wide range of operations. In recent years, with the increase of the strength of shrimp, the marine environmental conditions have become more complex. In order to improve the safety of marine production, fishing boats The tonnage and horsepower continue to increase, and the design of the net equipment also needs to be continuously updated and improved to improve its performance. Based on the above situation and comprehensive production experience, we believe that the rationality of choosing a fishing net for shrimps can be elaborated from the following aspects: 1. It is necessary to increase the power efficiency of fishing vessels as far as possible. According to experiments, the current fishing nets are used for fishing boats ( The power consumption of 80 horsepower to 150 horsepower is less than 10% of the rated horsepower, and the power utilization rate of fishing boats for trawl operations is 30% to 40%. In contrast, the economics of energy consumption in the trawling operation are very poor. Practice has proved that small horsepower fishing boats are economical and cost-effective for larger horsepower fishing boats. Therefore, only increasing the size of the gears will increase the width of the gear, and expand the area of ​​sweeping sea when it is towed so as to increase the power efficiency and output of fishing boats. That is, the mast that supports horizontal expansion should be lengthened and the specifications must be increased. In actual production, we believe that the mast should be a seamless steel pipe with an outer diameter of 110 to 159 meters, and the length should be 0.9 to 1.1 times the length of the fishing boat. 2. The ratio between the perimeter of the net port and the length of the net gear should be reasonable. The determination of the net length of the net net should be based on the length of the mast and the reduction factor of the net mouth, while referring to the horsepower of the fishing boat. The length of the net equipment is determined by the perimeter of the net mouth. The ratio between the length of the long and the net mouth is reasonable, and the net is stable and balanced when dragged, and the resistance is small, so it is not appropriate to suck sand and break the net. At present, we believe that the 80- to 150-horsepower fishing boat is better equipped with small nets and polycystic nets. Its main specifications and technical parameters are: 40 to 50 meters of net mouth to net sac mesh change. Between 0.07 and 0.10, the net cover length ratio is about 0.175, the net body length ratio is 0.32, the net pocket length is 0.485, and the net pocket is 3 to 10 different. In the operation process of the net, the water filtering performance is good, the webbing is not easy to suck sand, and the shrimp has good shrimp dragging effect. At the same time, the shrimp body has small damage and high integrity. 3. Properly equip and adjust the weight of the net in the trawl design of the net. It is for the general situation. In different tides and sea conditions, the buoyancy and buoyancy of the sea must be properly adjusted. Judging whether the weight of the gear is appropriate or not, can see whether the mast sinks after the gear is launched, as well as the degree of friction between the sinker's cement roller and the seabed, the type and quantity of each catch, and the suction conditions. The principle of deployment of floats in production is: During the towing process, Shen Zigang can effectively disturb the shrimps, but it should not be too heavy and increase the resistance of the nets. It should not be too light to achieve the effect of disturbing the shrimps. The specific adjustment methods are as follows: (1) When tides are small, small currents are slow, shrimps inhabit in the bottom layer or in the surface layer of sand and mud, and the range of active water layers is low; large tides and turbulent flows are urgent, shrimps tend to float, activities are smaller, and tides are high. . Therefore, large tides should be properly increased buoyancy, to increase the network port, expand the purpose of sweeping the sea. (2) In different sea conditions, there are no wind waves and seawater clarification. Shrimp often lurk in the surface of the sand bottom or slow down in the bottom. When there is wind and muddy water, the shrimps are active frequently and often drill river mud to swim in the waters. Near bottom or middle and lower floors. Therefore, buoyancy should be appropriately increased at this time to achieve effective fishing. (3) During the day and night changes, the shrimps tend to gleam at night and swim slowly on the bottom or the lower layer. The inhabited water layer is higher than the daytime, and this time should be slightly more buoyant than during the day. (4) When the netting sand suction and net breaking accidents are often encountered, the operation may be carried out on the soft mud. The hanging extension is too long, Shen Zigang is too heavy, the net weight is loose, the nets are swollen and the speed is too slow. They should be handled randomly. (5) Avoiding net-breaking accidents The lengths of the eight prongoids tied to the mast must be equal to each other in order to balance the force. In the production, the two prongs can be painted in different colors so that they can be used in the net. After landing in the sea to determine whether the settlement is normal, the distribution of floating gear must be balanced, to maintain the balance of the mast, otherwise the net will cause slanting movement in the sea, can easily cause flipping. Second, the determination and adjustment of towing speed 1. The speed of the fishing boat not only has a direct relationship with the ship type, model, power and other factors, but also with the specifications of the nets, the length of the traction net, and the float equipment of the net equipment. There are two types of tow speed: absolute speed and relative speed. The former is the displacement of the seabed by a boat or net gear within a certain unit of time. It is used to calculate the net area for sweeping nets; the latter is a boat or net gear. In one unit of time, the displacement generated by the flow of water is used to calculate the resistance of the net and the analysis of the mesh type.æ¡Trawling speed is generally referred to as absolute speed, and the position can be used to determine the ship's position to calculate the speed. 2. Trawling When towing, the adjustment of the speed of drag is determined by the subject, the fishery, and the state of the sea. The speed of the tow is determined mainly by the power and speed of the fishing boat's main engine. Crabs, crabs, and pelicans have relatively weak swimming capacity. They usually inhabit the bottom or surface layers of sand and mud. During operation, the cement wheel of the lower grade rolls over to make sure that shrimps are disturbed and bounced into the net. The absolute speed of the shrimp should be controlled at about 1 knot. The production practice proved that the speed was stable during the period from 1 to 1.5 knots, and the netting performance was good. If it was too slow, the catch area was low due to the small sweeping area; if it was too fast, the lower level would appear beating and part of the sinker Off-site, shrimp net production will decline significantly. 3. In order to maintain a certain speed, we must master the adjustment of the host speed according to the sea conditions. The method of determining the speed of dragging can be used to observe the flow of the water on the side of the ship and the movement of the water on the stern. It can also compare the speed of the ship with the same watercraft. When the use of fishing gear specifications for 2300 weeks ~ 2400 weeks, the 120-horsepower fishing boat general host speed adjusted at 1300 rev / min or more, 135 hp fishing boat host speed can be less than 1300 rev / min. The adjustment of the speed in actual production is quite flexible: (1) Tidal currents and top-stream trawls in fast sea areas, the main engine speed should be faster, the downstream trawl, and the host should be slower. (2) The stormy days, the wind trawl host slower speed, the wind trawl host speed should be faster. (3) Tide turbulence in the turbulent sea area should be faster than that of the tidal trawls in the rapid sea area. (4) The operation is usually performed in a soft muddy or sandy bottom (coarse sand bottom) fishery area where the sediment quality is poor. Generally, the drag speed is faster than that at the muddy bottom. The slow drag speed at the bottom of the soft mud may cause the Shen Zigang was stuck in the mud, so that it couldn't move. In the sand bottom, hard sand bottom operation too slow, easily lead to sand and netting accidents. Therefore, we should try to avoid the operations of ooze and increase the speed of towing. However, it is advisable to keep it at 1 to 1.5 knots. The towing time is usually about 3 hours.
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