Improvement and application effects of fishing gear for patinopecten yessoensis

Abstract: By analyzing and investigating the bottom condition of a mariculture area, distribution of Patinopecten yessoensis and fishing effects of gear in the Dalian Zhangzidao Group Company, a new type of high efficiency and energy-saving fishing gear was designed and improved. In order to prove that its structure is reasonable, two phases compared tests were executed in Liao Chang Yu Yang 15021. 　　There were two phases for the fishing gear design and improvement. In the first phase, based on the original fishing gear, multi-strand steel dredge was replaced by a spring loaded scallop toothed dredge. The external netting was made by high strength polyethylene ropes with a diameter of 5mm and installed with 10 rigid plastic floats of 120mm diameter. Meanwhile the mesh of the external netting was increased from 70mm to 75mm. Based on the first phase, the netting port cover area was increased. The gear frame was installed with a gear port chain, main gear crutch toothed dredge and sled. Middle netting was added between the external netting and the bottom netting. External netting was installed with 20 rigid plastic floats of 120mm diameter, arranged in two rows. In order to reduce the gear's weight, the fishing gear was designed with a wide head and narrow end. A pedestal car was installed in the bottom netting to reduce trawling resistance.　　According to two-phase improvement processes, two contrast tests were performed correspondingly. The original and the first improved fishing gears were used in the first phase test, the first and the second improved fishing gears were used in the second phase test. Each phase test lasted 10 days, and was conducted in 10 different sea areas (the bottom of the test mariculture area is sediment). Twice trawling in the same sea area of each day, two fishing gears were trawled per time, with the trawling speed being 4 kn, the trawling distance at 1nm per time, and the trawling track being different. After the trawling, the amount of scallops caught and broken and the contents of sediment were collected and recorded from each fishing gear. After several contrast tests, researchers obtained the following results. Compared to the old fishing gear, the first improved fishing gear increased average amount of fishing 36.5%, decreased breakage rates of scallops 49.4%, decreased contents of sediment 21.9%, and reduced fuel consumption per unit of trawling from 85.03 L/t to 61.41 L/t. Compared to the first improved fishing gear, the second improved fishing gear increased the average amount of fishing 102%, decreased breakage rates of scallops 161%, decreased contents of sediment 209%, and reduced fuel consumption per unit of trawling from 61.41 L/t to 46.28 L/t. The above results indicate that the improved fishing gear significantly reduces the energy consumption and increases the amount of fishing scallops, which have good prospects in application.