共查询到19条相似文献，搜索用时 93 毫秒
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为探索东海区日本方头鱼(Branchiostegus japonicus)三重刺网与海洋渔业资源的适宜性。2015年4月开展了3种型刺网(单片刺网、双重刺网和三重刺网)3种网目尺寸(50、60和70mm)的选择性试验。应用Normal、Lognormal、Gamma和Bi-normal 4种选择性曲线进行拟合,采用极大似然法估算模型参数研究3种型刺网的选择性。研究表明:3种型刺网共捕获种类33种,鲈形目最多(15种),鲉形目次之(5种),其中日本方头鱼为第一优势种,渔具具有较强的选择性;在同型刺网中,随着网目尺寸的增加(50~70mm),日本方头鱼优势体长组逐渐增大,网目尺寸对于其体长选择具有显著影响;日本方头鱼刺网最适选择性曲线为Lognormal曲线,3种型刺网选择性曲线基本相同;采用选择性曲线法推算出3种型刺网对日本方头鱼最佳网目尺寸依次为77.57、74.84和70.91mm。依据以上研究结果,针对日本方头鱼三重刺网,将其网目尺寸调整为70.91mm,可以有效保护当前渔业资源。 相似文献
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为支撑《全国海洋捕捞准用渔具目录》的实施与管理,本文利用套网法在黄海区海州湾海域开展了黄海双船变水层疏目拖网网囊选择性研究。在分析渔获的基础上,运用相对重要性指数(IRI)、Logistic模型等分析方法,获得了双船变水层疏目拖网渔获物种类组成、优势种和主要渔获物竹荚鱼(Trachurus japonicus)、小黄鱼(Larimichthys polyactis)和带鱼(Trichiurus lepturus)的选择性曲线。研究显示,随着网囊网目尺寸的增加,渔获物质量和逃逸率均逐渐增加;竹荚鱼、小黄鱼和带鱼的50%选择体长(L_(0.5))逐渐增大,且L_(0.5)与网囊网目尺寸呈线性关系;双船变水层疏目拖网网囊最小网目尺寸按照底拖网54 mm网目尺寸标准执行偏小。根据试验结果,结合小黄鱼、竹荚鱼和带鱼最小可捕规格,变水层疏目拖网网囊最佳网目尺寸分别为65.78、78.82和67.36 mm。在目前渔业资源状况下,为保护小黄鱼等中小型经济鱼类,建议将双船变水层疏目拖网网囊最小网目尺寸(网目内径)设定为66 mm。研究结果可为我国近海捕捞渔具管理以及渔业资源的可持续发展提供理论支撑。 相似文献
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陈敦隆 《中国海洋大学学报(自然科学版)》1978,(2)
刺网相对渔获率曲线的研究,对于刺网渔具设计和捕鱼技术有一定的实际意义。在刺网捕鱼理论的研究中,Φ.Ν.巴拉诺夫曾提出相对渔获率曲线的概念,同时根据力学相似原理及概率论理论给出了相对渔获率曲线的一种求法。本文则根据数理统计理论,研究刺网相对渔获率曲线的数学原理和实际求法。 相似文献
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结合银鲳和小黄鱼流刺网网目选择性试验,对夏季黄海南部沿海三层表层流刺网渔获物组成进行了调查分析.总共鉴定出渔获品种25种,其中优势种为梭子蟹(Portunus triuberbuculatus)、灰鲳(Stomateoidesnozawae Ishikawa)和银鲳(Stromatecoides argenteus),分别占总渔获量的59.2%,21.5%和11%,灰鲳体长分布范围为17～30 cm,优势体长范围为21～24 cm,占71.6%;银鲳体长分布范围为13～23 cm,优势体长范围为15～21 cm,占95.8%.数据分析表明,三重流刺网作业网具选择性较差,渔具兼捕种类多,捕获量大,占总渔获量的66.5%;渔获的灰鲳和银鲳处于生长型捕捞期,不利于资源的可持续利用,建议适当改良渔具,避免对其资源造成过度破坏. 相似文献
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参照渔业生物学、渔业资源解析学、数量遗传学等有关理论模型，并应用数值模拟方法，对长期选择性捕捞（重点为渔具选择性）是否参与造成了渔业资源的生物学变化（体长、性成熟等）进行某些基础性探索。设计了一个具有一定体长遗传特征的模拟鱼类种群，并利用一种具有固定选择性参数的拖网对其进行长期捕捞。结果表明，多年的持续的捕捞压力使得模拟种群中鱼类体长逐渐减小，减小的幅度随开发率的增大而增大，而终止捕捞后种群的体长并没有发生恢复的迹象，说明这种变化很可能伴随种群遗传的变化，具有自然不可逆性。 相似文献
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《中国海洋大学学报(自然科学版)》2016,(8)
本文根据2014年秋季青岛斋堂岛海域双桩竖杆张网的网囊网目选择性试验数据,运用PRIMER软件中的相似性分析、非参数多维标度分析和相似性百分比分析模块分析了张网渔具种类选择性。试验采用平行作业法,以传统网具(2a=16mm的菱形目网囊)作为对照网,设计了网目尺寸(2a)为30和35mm的菱形目网囊(以30D和35D表示)和网目尺寸(2a)为20、30和35mm的方形目网囊(以20S、30S和35S表示),进行选择性实验。研究显示:(1)35D、30S和35S渔获组成与对照网存在显著性差异,其余各网之间差异不显著。(2)改良后的试验网具能有效释放舒氏海龙;除20S组外,其余各试验网对方氏云鳚亦有较好的释放效果。(3)方形目网囊较相同尺寸的菱形目网囊具有更好的种类选择性;对相同网目形状的试验网囊进行比较,种类选择性随网目尺寸的增大而增大。(4)综合分析不同网具的渔获物组成和规格,在斋堂岛海域秋季小黄鱼、带鱼渔汛期,推荐使用30mm方形目网囊;方氏云鳚渔汛期,推荐使用20mm方形目网囊进行捕捞作业。研究结果表明,运用多元统计软件PRIMER进行张网渔具种类选择性分析虽然存在待完善之处,但该方法为本领域研究提供了有益参考。 相似文献
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为了获得山东近海四种头足类的选择性曲线,同时评估头足类种群胴长的相对密度分布.本研究根据2016年10月山东近海底拖网调查数据,基于Logistic选择性曲线和最大体周估算选择率方法,得出渔获物中日本枪乌贼(Loligo japonica)、金乌贼(Sepia esculenta)、长蛸(Octopus variabi... 相似文献
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分析了气动式波浪发电透平的特点、运行环境以及透平与振荡气流之间的相互作用过程,提出了描述透平稳态特性和动态特性的参数以及描述透平运动性能的特性曲线,推导得出透平的稳态最佳工作点,最后提出了透平的匹配设计方法。该设计模型的建立,对波浪透平的研究和设计具有较重要的指导意义 相似文献
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Fuel consumption in fisheries is a primary concern because of its effects on the environment and the costs incurred by fishermen. Many studies have been conducted to reduce the fuel consumption in fishing operations. Fuel consumption due to fishing gear during a fishing operation is generally related to the hydrodynamic resistance on the gear. This means that fuel consumption is proportional to the drag created by the towing speed. Based on numerical methods, this study suggests a new approach to reduce fuel consumption in fisheries. The results of the simulation are in good agreement with those of model experiments. The total as well as partial resistance forces on the gear are calculated by simulation. The simulation results suggest improved materials and gear structure for reducing the hydrodynamic forces on the gear while maintaining gear performance. The method for assessing the gear performance involves measuring the height and width of the net mouth. Furthermore, this study investigates the efficiency of a low-energy trawl from an economic point of view. The findings of this study will be useful in reducing greenhouse gas (GHG) emissions in fishing operations, and thereby contribute toward lowering fishing costs by saving fuel. 相似文献
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《Marine Policy》2013
This study examined the feasibility of gear substitution as a means to reduce bycatch and habitat impacts of fisheries, using a social–ecological systems approach. The U.S. west coast sablefish fishery is an excellent subject for this study, because it permits three different gear types and has a problem with bycatch of overfished species. Bycatch rates were highest in trawls and lowest in pots. Combining interview data with findings from a previous study, affirmed that habitat impacts were highest with trawls and lowest with longlines. Interviews with 44 individuals analyzed using grounded theory yielded several common themes in the opinions of gear substitution. Positive opinion themes included that it would allow better management of the fish populations by reducing bycatch and would allow more business options, flexibility, and increased profit for some trawlers. The main negative opinion theme was that gear substitution could decrease landings needed to support shoreside infrastructure. Most stakeholder groups saw some benefit in gear substitution. Notably, the trawlers voiced a unanimous preference for converting to pots rather than longlines. A scenario analysis revealed that the preferable management option would be long-term gear conversion, but incentives are likely to be an important means of encouraging gear conversion. This ecological impacts rapid assessment provided a regional evaluation of bycatch and habitat impacts that had never been conducted before for these gear types. It also provided scientific support for a regulatory change that legally allows trawlers to practice gear substitution. 相似文献
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副渔获物对渔业资源的影响及其减少方法的探讨 总被引：1，自引：0，他引：1
由于渔具不同的选择性和多鱼种鱼类共栖 ,人们在对目标种类进行捕捞时 ,不可避免地产生副渔获物及其抛弃。由于渔业资源的下降和人们对海洋环境保护意识的加强 ,副渔获物及其抛弃问题日益成为人们关注的焦点。本文对世界范围内的渔业活动所产生的副渔获物进行分析 ,根据副渔获物的种类、被抛弃情况和原因以及对渔业资源的影响 ,提出了减少副渔获物和抛弃的方法。 相似文献
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Robert Kilpatrick Graeme EwingTim Lamb Dirk WelsfordAndrew Constable 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):486-491
Studies of the interactions of demersal fishing gear with the benthic environment are needed in order to manage conservation of benthic habitats. There has been limited direct assessment of these interactions through deployment of cameras on commercial fishing gear especially on demersal longlines. A compact, autonomous deep-sea video system was designed and constructed by the Australian Antarctic Division (AAD) for deployment on commercial fishing gear to observe interactions with benthos in the Southern Ocean finfish fisheries (targeting toothfish, Dissostichus spp). The Benthic Impacts Camera System (BICS) is capable of withstanding depths to 2500 m, has been successfully fitted to both longline and demersal trawl fishing gear, and is suitable for routine deployment by non-experts such as fisheries observers or crew. The system is entirely autonomous, robust, compact, easy to operate, and has minimal effect on the performance of the fishing gear it is attached to. To date, the system has successfully captured footage that demonstrates the interactions between demersal fishing gear and the benthos during routine commercial operations. It provides the first footage demonstrating the nature of the interaction between demersal longlines and benthic habitats in the Southern Ocean, as well as showing potential as a tool for rapidly assessing habitat types and presence of mobile biota such as krill (Euphausia superba). 相似文献
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In this paper we review levels of net loss, what happens to the gear once it has been lost, and the resulting levels of ‘ghost catches’ made in passive net fisheries in the EU. We also consider ghost catches resulting from lost gear in other types of fisheries, and the extent to which the value of ghost catches has been quantified. We consider why fishing gear is lost, and profile common management responses. We present a cost benefit model to assess the relative cost effectiveness of different management measures, and suggest that gear retrieval programmes may provide less value for money than other management responses. 相似文献
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本文在叙述ＣＴＤ剖面仪和传感器校准方法的基础上,介绍了当前国内外ＣＴＤ校准技术研究和校准设备的现状。提出了我国应加强ＣＴＤ传感器动态校准的研究,同时,应研制精度慢温盐水盐力罐,用于在实验室内研究建立ＣＴＤ传感器数学模型的方法。 相似文献
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The current study provides long-term catch rate and biological data for tiger sharks Galeocerdo cuvier caught in the KwaZulu-Natal bather protection programme. Between 1978 and 2014, 1 760 G. cuvier were caught in nets and between 2007 and 2014, 108 G. cuvier were caught on drumlines. Standardised catch rates increased significantly over time (p < 0.001) for both small (≤180 cm precaudal length, PCL) and large sharks (>180 cm). There was also a significant temporal increase in the mean size of sharks across gear types (p < 0.001). A quasi-Poisson generalised additive mixed model showed that the deployment of drumlines had no significant effect on the catch rate of sharks in nets. The nets, however, caught significantly larger sharks (mean 184.5 cm, SD 39) than did drumlines (mean 138.6 cm, SD 36.5; p < 0.001). The size frequency of the catch was unimodal and females significantly outnumbered males in both gear types. Few young-of-the-year (0.8%) or mature sharks (1.8%) were caught. Only 23 (4.7%) of the 486 sharks tagged and released were recaptured, with the majority (87.0%) of those recaptured <150 km from their original tagging locality. The results from this study suggest an increasing local population trend in G. cuvier along the KwaZulu-Natal coast. 相似文献
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The underwater tapping machine is composed of a center bit,a tapping cutter,a sesl box,a main drive box,aboring bar assembly,a envelop,a gear case,a counter and so on.The drive system in underwater tapping machine consists of a worm drive,a gear drive system and a screw drive.The worm drive is in the main drive box.The worm is connected with a hydraulic motor and driven by the hydraulic motor.The gear drive system is a combined gear train which is the combinations of the fixed axes and differential gear train in the gear case.On the one hand,by means of the fixed axes gear trains the turn and power of transmission shaft are transferred to the boring bar and the screw rod,causing differential tam between the boring bar and the screw rod.On the other hand,the turns of the boring bar and the screw rod are transferred to the differential gear train.The differential gear train is used to drive a special counter to count axial travel of the boring bar.The screw drive is composed of a feed screw and a nut on the boring bar.There is the differential turn between the boring bar and the feed screw.By means of the nut,the boring bar can feed automatically.With the movement of the sliding gear 7 in the gear case,the designed drive system can also be provided with the ability of fast forward and fast backward movement of the boring bar in its idle motion,restdting in the increase of the tapping efficiency. 相似文献
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Randall ReevesCheryl Rosa J.Craig GeorgeGay Sheffield Michael Moore 《Marine Policy》2012,36(2):454-462
The objective of this paper was to investigate and illustrate how insights gained from experience managing human activities in order to protect North Atlantic right whales (Eubalaena glacialis) along the heavily industrialized east coast of North America might be applied in the Arctic, where bowhead whales (Balaena mysticetus) face some of the same risks as right whales. The reduced extent and thickness of sea ice and the resultant longer open-water season have major, complex implications for the Arctic marine ecosystem. Increased maritime ship traffic and commercial fishing in the Arctic are bound to affect bowheads and Native (indigenous) hunting communities who depend on whales for subsistence and cultural identity. Bowheads and right whales were greatly depleted by commercial whaling in the 19th and early 20th centuries. While the Western Arctic bowhead population has been recovering steadily in recent decades, North Atlantic right whales remain highly endangered because of persistent lethal and sublethal vessel strikes and frequent entanglement in commercial fishing gear. Entanglement can be transitory or persistent, with debilitation lasting for months before the animal finally succumbs. Vessel strike and fishing gear trauma has been documented in bowheads, but at a much lower rate than in right whales. Initiatives intended to mitigate the impacts of ship traffic on North Atlantic right whales have included speed limits and routing changes. Those meant to reduce the incidence and severity of entanglements include the modification of gear design and gear deployment practices. Management measures need to be considered in advance in the Arctic in order to minimize the risks to bowhead whales as shipping and industrial fishing expand in the Arctic with ice retreat. 相似文献