仿生机器鱼胸尾鳍协同推进的水动力学分析

利用CFD技术对仿箱鲀科胸尾鳍协同推进机器鱼的水动力学特性进行分析,将整个机器鱼放入流场,对其胸鳍推进模式、尾鳍推进模式和胸尾鳍协同推进模式的水动力学特性进行对比,得出不同模式下机器鱼水动力学的变化规律。分析得出,在压力变化云图中,胸尾鳍协同推进产生的压力变化最为复杂;在速度涡量变化图中,胸尾鳍协同推进产生最为复杂的涡量变化,胸鳍运动产生的涡会逐渐脱落向后移动,与尾鳍产生的涡互相作用,增加尾鳍的推力,从而证明胸尾鳍协同推进模式是一种高效的推进机制。     

复合驱动仿生胸鳍机构设计与水动力研究

针对仿鱼型海洋探测机器人低速时的机动性问题,受鹞鲼鱼类依靠胸鳍摆动实现各种水下运动的启发,设计出一种基于共融理论的复合驱动刚-柔多体耦合仿生鱼胸鳍机构。通过构建基于三维非定常湍流控制方程组的柔性鳍摆动系统水动力学模型,研究仿生胸鳍柔性鳍面摆动时周围压力和速度场的变化情况,分析不同摆动幅度和频率下鳍面的水动力学特性,揭示仿生鹞鲼机器鱼的水下运动机理,对摆动胸鳍的水动力进行仿真。结论表明:鳍面摆动时周围的漩涡能够引起胸鳍面上推力、升力及侧向力按类似正弦变化,而推进力和侧向力的大小随摆动幅值和摆动频率增加而增大。     

鱼梁航运枢纽鱼道及鱼类增殖保护站设计浅述

航运枢纽的建设对鱼类生态环境及鱼类资源影响较大，为减缓工程对鱼类的不利影响，文章通过综合分析，提出采取修建过鱼设施和建立增殖保护站、开展人工增殖放流为主要鱼类保护措施，并结合鱼梁枢纽工程，对鱼道结构及布置、增殖保护站布置及生产方式等设计进行介绍。     

Spatial fisheries ecology: Recent progress and future prospects

We review recent progresses made in the study of fish distribution and survival over space — i.e., fisheries spatial ecology. This is achieved by first surveying the most common statistical approaches and relative challenges associated with the analysis of fisheries spatial data, loosely grouped in geostatistical and regression approaches. Then we review a selected number of case-studies implementing the discussed techniques. We conclude by proposing new areas of statistical and ecological research to further our understanding of how fish distribute and survive in space. This review serves a dual purpose by emphasizing the scientific importance of studying spatial interactions to better understand the temporal dynamics of fish abundance, and by promoting the development of new analytical and ecological approaches for the analysis of spatial data. Through our survey we cover different statistical techniques, marine ecosystems and life stages. This analytical, geographic and ontogenetic variety is also purposely selected to highlight the importance of comparative and multidisciplinary studies across diverging ecological disciplines, ecosystems and life stages. Besides having a general ecological relevance this review also bears a more applied significance, owing to the increasing need for protecting renewable marine resources along with their primary habitat.     

Recreational Leasing of Alaska Commercial Halibut Quota: The Early Years of the GAF Program in Alaska

The Pacific Halibut Catch Sharing Plan formalized the process for allocating halibut between the Alaska commercial and recreational charter sectors. It included a new program intended to allow for “flexibility” through inter-sectoral trading, permitting charter operators to lease commercial halibut pounds to relax client harvest restrictions. Here we evaluate the first two years of lease market activity and participation. Participation from some commercial quota holders in the lease market suggests that the program provided beneficial flexibility; in fact, the number of transfers to the charter sector was greater than transfers within the commercial sector for some quota types. We also identified a high proportion of self-leasers. However, transfers to the charter sector were on average smaller than within-sector commercial transfers, and total poundage leased by the charter sector was low compared with commercial transfers. Usage of leased quota by the recreational charter sector enables the harvest of larger fish or additional fish, and provides flexibility in catch composition on halibut closure days. Finally, the value-per-pound may be higher in the charter sector, as commercial-to-charter transfer prices approached the commercial ex-vessel price.     

新型双机双筒高效吸鱼泵及其控制系统设计

新型高效吸鱼泵由双真空泵、双吸鱼筒组成,利用双筒交替吸鱼、排鱼,可实现连续鱼虾起捕,其效率是单筒间歇式吸鱼泵的1.5倍以上,有效解决了传统真空吸鱼泵存在的效率低、功耗大的问题;双真空泵可互为备用,也可轮流使用,通过冗余设计提高设备的可靠性,这对远洋捕捞业尤为重要;该吸鱼泵采用真空负压抽吸和零压排放原理,有效提高活鱼成活率;主吸鱼管采用套管式结构,可在水平、垂直方向灵活伸缩;控制系统采用全程自动化控制。     

Ludwig?s Ratchet and the Collapse of New England Groundfish Stocks

The stocks of principal groundfish species off New England have collapsed, creating economic hardship and dislocation in fishing communities from Rhode Island to Maine. In this article we analyze the causes of this collapse using the ?ratchet effect? described by Ludwig, Hilborn, and Walters (1993) as a framework. According to Ludwig, Hilborn, and Walters, powerful economic and political interests drive fisheries to overcapitalize and overexploit despite scientific evidence that stocks are declining. When the fishery is no longer economically viable, governments provide financial assistance to minimize economic hardship. When stocks increase there is another rush to invest, and the cycle repeats itself. The history of groundfish management in New England conforms well to this model. Optimism among fishers and government over U.S. control of this fishery in 1977 stimulated successive rounds of investment that built up excessive fishing capacity despite warnings from scientists that stocks were becoming weaker. Management regimes designed by the New England Fishery Management Council were ineffective in constraining fishing effort. Collapse of the stocks has led to severe restrictions on fishing and to government assistance. We suggest that the integration of science, management, and harvesting sectors through ecosystem-based management offers the best means of avoiding similar situations in the future.     

Experimental investigation on hydrodynamics of floating cylinder in oscillatory and steady flows by forced oscillation test

In this paper the hydrodynamic characteristics of a floating cylinder are investigated via forced oscillation experiments in towing tank. The effects of Keulegan–Carpenter number, Reynolds number, reduced velocity and overtopping on hydrodynamics of the floating cylinder in oscillatory and steady flow are studied. The results show a considerably difference of the hydrodynamic characters between the floating and the fully immerged cylinders due to the influences of free surface. The growth of the reduced velocity, a proven notable effect on hydrodynamics, will lead to the increase of added mass coefficient and the decrease of drag coefficient. Meanwhile the overtopping, a particular phenomenon for the floating cylinder, render the added mass coefficients reach up to 3.6 while for the drag coefficient small influences were made.     

Numerical modelling of fish eggs dispersion at the Patos Lagoon estuary — Brazil

The Patos Lagoon estuary is the most important nursery ground for commercially relevant species of fish and crustaceans in the South of Brazil, maintaining fisheries that sustain 3500 fisher families throughout the Rio Grande do Sul State coastline. Around 80% of the interior estuarine area is very shallow (< 2 m), and recruitment of fish eggs and larvae to the inner parts of the Patos Lagoon estuary is directly related to the circulation pattern in the area, which is controlled by local and non-local wind effects and freshwater discharge. The objective of this study is to investigate the processes controlling the transport of estuarine dependent fish eggs between the Atlantic Ocean and the Patos Lagoon estuary.An integrated numerical system based on a bi-dimensional hydrodynamic model and a Lagrangean transport model of passive particles is applied to a selection of scenarios representing the passage of weather fronts over the area. At this stage, fish eggs are represented as buoyant passive particles. Modelling results are compared against field data for the period under investigation (September/October 1999) and historical records. Short term results are analysed in terms of the meteorological conditions (wind direction, intensity and duration) controlling the transport of eggs to the inner parts of the estuary and the extension of their excursion. This experiment is the first attempt to couple biological and physical information to study fish eggs transport, and to enhance the current knowledge about recruitment of important fisheries resources in southern Brazil.     

渔船冷藏鱼舱蒸发盘管传热特性仿真研究

吸收式制冷技术可利用渔船柴油机尾气中的热能产生冷量对渔获物进行制冷保鲜，是一种能源循环利用的绿色节能技术。冷藏鱼舱内的制冷通常采用蒸发盘管形式，由于吸收式尾气制冷装置的制冷功率受限于渔船主机功率，为保证渔获物得到足够的冷量，应对鱼舱内的蒸发盘管布置进行优化。本文利用专业多物理场仿真软件，根据上海市36m标准化桁杆拖网渔船冷藏鱼舱的实际布置和装载情况，基于氨-水吸收式制冷方式，在渔获物模型简化、多种盘管布置下的温度场分布、蒸发温度对温度场影响等方面开展研究，对比研究了蒸发盘管总长不变的情况下分别布置在鱼舱顶部、布置在侧壁和布置在顶部与侧壁三种方式下的制冷效果，结果表明盘管全布置在舱顶对中心渔获物冷却效果最好。