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Revealing the Fluttering Motions of Mid-Water Trawl codend Through Sea Trials:Case Study of Antarctic Krill Trawl codend

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Journal of Ocean University of China 2023年第2期22卷 555-564页

作者： LIU Wei TANG Hao NYATCHOUBA NSANGUE Bruno Thierry ZHANG Feng YIN Liqiang XU Liuxiong HU Fuxiang LIU Pengfei College of Marine Sciences Shanghai Ocean UniversityShanghai 201306China National Engineering Research Center for Oceanic Fisheries Shanghai 201306China Key Laboratory of Oceanic Fisheries Exploration Ministry of Agriculture and Rural AffairsShanghai 201306China The Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources Shanghai Ocean UniversityMinistry of EducationShanghai 201306China Scientific Observing and Experimental Station of Oceanic Fishery Resources Ministry of Agriculture and Rural AffairsShanghai 201306China Faculty of Marine Science Tokyo University of Marine Science and TechnologyMinatoTokyo 108-8477Japan Tendering Office Shanghai Ocean UniversityShanghai 201306China

The dynamic coupling between the fluttering motions and hydrodynamic characteristics of codend is essential in understanding the trawl selectivity through fish response and the drag force acting on the whole *** study investigated the effect of towing speed,warp length,warp tension,and catch size on the fluttering motions of Antarctic krill trawl codend during net shooting,towing,and hauling by using sea trial *** time-periodicity of codend oscillation was analyzed by the Morlet wavelet transform *** indicated that the period of codend oscillation was between 50 s and 90 s and showed an increasing trend with the warp tension but a decreased value at the towing *** coefficient amplitude of codend oscillation was between 0 and 4 at the net shooting and hauling stages,and between 0.2 and 0.6 at the towing *** amplitude of codend oscillation increased with the warp tension,towing speed,and catch size,but decreased with the increase of the warp *** addition,the period of codend oscillation increased with the towing speed at the net shooting and hauling stages,but decreased at the towing *** results from codend fluttering motions can improve the understanding of fish behavior and gear shape that modify the hydrodynamic force on the codend instantaneously.

关键词： codend fluttering motions sea trials Morlet wavelet periodicity

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Square mesh codend improves size selectivity and catch pattern for Trichiurus lepturus in bottom trawl used along Northwest coast of India

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Aquaculture and Fisheries 2023年第5期8卷 564-571页

作者： Madhu Vettiyattil Bent Herrmann Meenakumari Bharathiamma ICAR-Central Institute of Fisheries Technology MatsyapuriWillingdon IslandCochinKerala682029India SINTEF Ocean Fishing Gear TechnologyWillemoesvej 2Hirtshals9850Denmark University of Tromsø BreivikaTromsø9037Norway DTU Aqua Technical University of DenmarkHirtshals2800Denmark Division of Fisheries Science Krishi Anusandhan Bhawan-IIIndian Council of Agricultural ResearchNew Delhi110012India

The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study.A 34 m high opening trawl was used,which is a common design used by fishermen operating along the northwest coast of India,and the cover codend method was employed to determine codend *** with the changes in the length at 50%retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends,indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the *** mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes,however,it is observed that individuals at commercial length are also *** results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species,given its estimated length at first sexual maturity of 61.2 *** is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of *** of the study will help as a baseline for gear-based regulations in the region.

关键词： Size selectivity Trichiurus lepturus Square mesh codend India

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Assessment of the Selective Properties and Optimization of Mesh Size of Pelagic Trawl codends, Used for Fishing Mackerel (Trachurus Spp) in the Gulf of Guinea

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Open Journal of Marine Science 2013年第2期3卷 103-111页

作者： Njomoue Pandong Achille Ebeku Ngomo Christopher Tcham Leopold Department of Fisheries Faculty of Industrial Engineering University of Douala Douala Cameroon

Over the past few decades, it has become widely recognized that the management strategies of world fisheries must ensure sustainability of target species. The intervening years have seen many improvements to the concept of gear selectivity and methods for measuring the selectivity of fishing towed gears. Improved understanding of the principles of the selection of fish by gears has changed the list of parameters which are known to have a significant effect upon selection. The recent development of new mathematical models and the increased availability of powerful computers have resulted in improvements in the analysis procedures for the data produced to measure a gear’s selectivity. The catch of mackerel in the gulfofGuineahas steeply declined during the last two decades, and resource management is clearly required. Therefore, the need for evaluation of trawl codends used in this fishery and the potential improvements to their selectivity are of prime importance. In this paper, we use semi-empirical models to define selective properties of pelagic trawl codends targeting black mackerel (Trachurus spp) in theGulfofGuinea. These properties are determined using the experimental and theoretical methods of assessing the parameters of the selectivity curve, and by plotting the curve. Selection parameters were obtained by fitting a logistic equation using a maximum likelihood method. Trawl codend selectivity is estimated for 17 internal diamond mesh sizes in the range 47 - 79 mm. Using the basic selectivity equations, we determine the needed mesh size A = 58 mm for fishing mackerel in the gulf of Guinea. This nominal mesh size gives room for nj = 0.1 catch of juveniles, which not exceeds the allowable proportion [nj] = 0.1. To provide resource conservation, there is the need to make amendments in the fishery regulations for more rational exploitation of mackerel stoks, because the currently use nominal mesh size A = 56 mm is rather unselective.

关键词： codend Selectivity Mesh Size Gulf of Guinea Selectivity Models

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