Factors affecting the characteristics and propagation of voltage gradient fields from electric fishing anodes

Abstract  The relationship between applied anode voltage, ring anode diameter and distance to specific voltage gradient values was modelled from empirical measurements. The model allowed distance to specific voltage gradients to be predicted. Varying the anode to cathode resistance ratios had a significant effect on the electrical potential of the anode and thus the voltage gradient projected from it. The voltage gradient profile of twin anodes was reduced when they were held in close proximity (<5 m).     

Dual-gear approach for calibrating electric fishing capture efficiency and abundance estimates

Abstract  Electric fishing depletion systematically underestimates fish abundance in streams. Electric fishing mark-recapture estimates are unbiased, but only when performed over several days to allow marked fish to recover from electric fishing. A mark-recapture procedure that can be performed in 1 day and produces unbiased population estimates is described. It involves minnow trapping, marking and releasing juvenile salmonids in a stop-netted reach, followed by electric fishing the reach 1 h after release of marked fish. Recapture of marked fish during electric fishing can form the basis of a dual-gear mark-recapture population estimate, or an unbiased estimate of electric fishing capture efficiency. The marking technique did not affect short-term catchability of the target species ( P  =   0.823), and provided unbiased estimates of capture efficiency (0.38–0.40) that were similar to those documented by other researchers. However, local validation to confirm equal catchability of marked and unmarked fish, as described in this study, is recommended.     

灯光围网渔船采用电力推进系统论证

为解决柴油机推进船舶存在装机功率大、体积笨重、造价高、节能环保性能差等问题,研究了电力推进装置在渔船上的应用,阐述了船舶电力推进的发展现状以及推进系统特点,论证了一条灯光围网船渔船营运过程中航行、作业以及停泊等情况下,电力推进装置渔船可以根据用电需求选择发电机运行台数,使发电机组一直运行于高效工作区。通过与常规柴油机在装机功率、发电机负载、燃油消耗的比较和推进系统的分析选择,证明了电力推进装置具有较高的节能性和经济性,体现了其在灯光围网渔船上应用的优越性。     

Global fishing capacity and fishing effort from 1950 to 2012

Global marine wild‐capture landings have remained relatively stable for >20 years; however, there is a lack of credible fishing capacity and effort information required to assess the sustainability and efficiency of the global fleet. As such, we estimated global fishing capacity and effort from 1950 to 2012 using a relatively comprehensive database developed by the FAO, supplemented by other data sources. Using random sampling techniques, we estimated the uncertainty surrounding many of our estimates enabling the identification of deficiencies and limitations. Global fishing capacity and effort increased rapidly from the late 1970s through to around 2010 before stabilizing. The Asian fleet is more than an order of magnitude larger than any other region in both capacity and effort, and continues to increase. Most other regions have stabilized, and there have been considerable declines in Europe and, to a lesser extent, in North America. Developed nations, as a whole, have decreased in both measures in the recent years and are responsible for the stabilization of the global trend. Developing and undeveloped countries are still increasing with the former having the largest fleet and showing the greatest relative increase with the socioeconomic impacts of reversing these trends likely to be high. The efficiency of the global fleet, in terms of watt days of fishing effort per tonnage of wild marine catch, is now less than in 1950 despite the considerable technological advances, and expansion throughout the world's oceans, that has occurred during this period of time.     

Evaluation of single-pass backpack electric fishing for stream fish community monitoring

Abstract  Data from Lake Ontario tributaries were used to evaluate the efficacy of single-pass backpack electric fishing for stream fish monitoring by: testing the relationship between single-pass catch-per-unit-effort (CPUE) and multiple-pass-based population estimates; comparing species richness estimates derived from single-pass and multiple-pass data and assessing the concordance of fish assemblage patterns described using single-pass and multiple-pass data. Significant correlations were calculated between single-pass CPUE and removal-based population estimates for total catch, 15 species, six taxonomic families, five feeding and four reproductive guilds and tolerant/intolerant species. Strong correlations were more commonly associated with the abundance of individual species than other metrics. Capture probability was not affected by stream size or habitat complexity for most measures. Species accumulation curves and significant correlations ( r ² = 0.9) between single-pass and multiple-pass electric fishing indicate that single-pass surveys provide a representative index of species diversity. In addition, within and among-site variation in fish community composition based on single-pass and multiple-pass data were similar.     

36米多用途渔船柴电混合动力推进系统方案设计

为解决传统柴油机推进系统难以满足多用途拖网渔船工况多且复杂以及特殊水域噪音控制要求高的问题,本研究从安全节能环保的角度出发,研究团队研发设计出多用途渔船柴电混合动力推进系统.船舶采用柴油机和轴带异步发电/电动机结合的推进形式,采用双输入单输出齿轮箱,轴带异步电机既可由柴油发电机组供电,也可由锂电池组供电.常规航行工况时...     

A comparison of electric fishing and gillnetting to examine the effects of anthropogenic disturbance on riverine fish communities

Abstract Quantitative electric fishing and multiple mesh-size gillnetting of fish communities in the Hawkesbury-Nepean River system, near Sydney, were carried out upstream of, within and well below each of three major points of treated sewage effluent discharge. Approximately half of the fish sampled were caught by electric fishing, comprising 515 individuals in 3 h of electric fishing (172 fish per hour). The remaining 439 fish were caught in 72 h of gillnetting (six fish per hour). In total, 16 fish species were collected by electric fishing and only seven species by the gill nets. Differences were found in the total abundances and numbers of species collected by each method in relation to points of treated sewage effluent discharge, but neither community variable showed consistent differences between the areas above, within and well below points of treated sewage effluent discharge in all three river regions. However, classification and ordination of electric fishing catch data produced distinct fish community groups in relation to sewage discharge, while similar analyses of the gillnetting data failed to reveal such differences in community structure. It was suggested that the increased sampling efficiency of electric fishing, both in terms of the number of fish sampled per unit effort and number of species collected, allowed for significant increases in the power of univariate and multivariate analysis methods in detecting such environmental disturbances in large rivers.     

基于轴功率测量的渔船动力装置优化配置研究

渔船船、机、桨不匹配现象较为普遍,不但降低了渔船的经济效率,而且给渔船的安全生产带来隐患.轴功率是反映船舶柴油机及其动力装置最重要的性能参数之一.通过对渔船主机轴功率进行实船测试,不仅可以发现主机的技术状况是否良好,而且可以判断船、机、桨的匹配情况,为船厂和用户提供可靠的试验数据,以便及时进行修理或调整,保证主机和整个船舶始终处于良好的技术状态.本文结合船舶轴功率-转速特性图,对实现渔船动力装置优化配置进行了理论分析,结论有利于选择最佳工况、提高整个动力装置的经济性.     

两种底拖网渔业资源调查船捕捞效率标准化分析

渔业资源科学调查是开展渔业资源状况评价、物种保护和管理等分析的重要数据来源，当调查方式发生变化时，维持数据的时间一致性至关重要。因此，原位试验获取不同调查方式的捕捞效率校正因子（fishing power correction，FPC）成为资源状况评价的先决条件。本研究通过平行拖网对比试验分析了科学调查船“中渔科211”（试验船）和生产性渔船“浙嵊渔10201-10243”（标准船）在开展渔业资源调查时对不同种类或类群的渔获率差异。结果表明，标准船和试验船平均渔获率分别为（47.27~1836.72）kg/nmile²和（12.28~311.85）kg/nmile²。标准船主要种类为小黄鱼（），渔获率范围分别为（1.17~1113.26）kg/nmile²和（0~565.39）kg/nmile²；试验船主要种类为鳀（），渔获率范围分别为（0~277.59）kg/nmile²和（0~125.24）kg/nmile²。2种调查方式对不同种类/组的渔获率随深度变化趋势出现分化，其中总渔获率、鱼类、银鲳（Apogonichthys lineatus）、绿鳍鱼（）8个种类/组表现为相似的变化趋势；甲壳类、细点圆趾蟹（Erisphex pottii）5个种类/组变化趋势相反；头足类、小黄鱼、龙头鱼在各深度变化具有异质性特征。这种变化与网口垂直扩张和所在水层位置有关。均值比和Kappenman方法估计的总渔获率FPC分别为0.35（95%置信区间为0.24~0.61）和0.43（95%置信区间为0.27~0.70），各种类渔获率均值比结果显示，FPC变化范围在0.03~2.61，其中总渔获率、鱼类、头足类、小黄鱼和绿鳍鱼达到显著水平，建议对上述种类的资源丰度指标年际变化趋势分析时进行数据校正。标准船以近底层种类为调查对象，尤其在捕获经济种类方面表现出优良性能，但对完整生态系统代表性较弱。试验船适合浅水区调查，在深水区由于网口垂直扩张不足，且网位存在上浮现象，难以反映近底层生态系统。     

Inter-calibration of three electric fishing techniques to estimate 0+ juvenile fish densities on sandy river beaches

Abstract  The efficiencies of three different techniques for 0+ fish point abundance sampling by electric fishing were tested on a sandy beach of the Morava River, Czech Republic. During direct electric fishing (DE), the operator immerses an anode fastened on an extension pole. During thrown anode electric fishing (TE), the anode is thrown at a distance from the bank. During remote electric fishing (RE), a pre-positioned anode is activated after allowing sufficient time for fish to recolonise the area. The DE technique was found to disturb fish and that fish tend to escape, thereby reducing its efficiency (30% of efficiency of RE). There was no significant difference in relative abundance estimates or size structure of assemblages between DE and RE, but TE seemed to be a species selective technique on sandy river beaches, significantly overestimating relative abundance of bleak. Of the three techniques tested, RE was the most efficient and if time required for deployment could be reduced, it would be also the most suitable for monitoring 0+ fish assemblages on sandy river beaches.     

Factors affecting the fishing power of sardine fishing vessels and implications for the management of the fisheries on Lake Kariba, Zimbabwe

Abstract The factors important in determining fishing power in the Lake Kariba sardine, Limnothrissa miodon (Boulenger, 1906), fishery were identified using data from the major fishing area of the lake, the Kariba basin, for the periods 1980–1982 and 1988–1990. Comparisons were carried out using fishing power calculated from the mean catch of some standard vessels. Three methods were used for identification of the important attributes. Analysis of variance (ANOVA) was carried out for each component to compare the mean fishing power at all levels within each variable. Multiple regression analysis was used to build predictive models and to determine the factors which best predict fishing power. Factor analysis was used to ordinate vessel types and examine any vessel groupings related to fishing power. Factor analysis showed that vessel and net size were the most important variables. Vessels without engines for propulsion, of low value and without radios had less fishing power than the other vessels in the fleet. Vessels from the same company had similar fishing power, suggesting that some unmeasured variable such as quality of management linked to the fishing companies had a significant effect on catch. The factors which were important in determining catch were length of vessel, depth of the net, presence and absence of echo sounder, mobility, the type of light, number and wattage of the underwater lights in the 1988–1990 fishing period. Vessel length and net category were most important in the period 1980–1982. The models accounted for between 37.6 (1981) and 61.2% (1988) of the variation in fishing power. During the development of the fishery, there has been a change from purse seine to lift nets, and increases in the use of echo sounders, engines for the propulsion of vessels and radios, all of which could have increased effective fishing effort.     

挪威海洋捕捞及渔船管理概述

本文概要介绍了挪威海洋捕捞业和渔船管理状况:2011年,捕捞量230万t,产值159亿挪威克朗(约26.8亿美元);渔民数量12 791人,渔船数量6 252艘;近10年的捕捞量基本稳定,年均捕捞量为250万t,与此同时,渔船和渔民数量则呈持续下降态势,说明挪威渔船的捕捞能力显著增强,捕捞效率明显提升。挪威的渔业管理制度和法规建设比较完善,这为控制捕捞强度、保护海洋渔业资源奠定了法律基础。挪威的经验具有借鉴意义。我国现阶段以实行渔船控制等投入控制制度为主、其他管理方式为辅的渔业资源管理制度,比较符合我国实际。实践证明,减船转产政策是控制捕捞渔船规模和降低海洋捕捞强度行之有效的措施之一。     

1985~1986年长江口生态系统能流网络分析

中国近海基于北斗卫星导航系统的渔船监控系统(vessel monitoring system,VMS),在渔船管理和应急救援中发挥了重要作用,同时北斗船位数据还包含位置、时间、航速、航行等信息,可进一步用于渔船航次信息挖掘与分析。文章首先把海陆边界划分成多个0.1°×0.1°的港口格网,然后根据格网与渔船轨迹相交关系,提取海南省2016年的全部航次。海南省渔船以小型为主,航次时间1~5 d占全部航次数的71.8%,各作业类型航次时间平均都在5 d左右;受休渔期、节假日、台风等天气影响,航次频数各月变化有3个峰值和3个谷值;儋州、三亚、文昌3个海南省返回港的航次占航次总数的62.9%,海南省出港非海南省返港的航次主要集中在北海市、阳江市、惠州市等港口。文章基于北斗船位数据的航次提取方法具有普适性,可以直接应用到安装有北斗终端的近海其他省市的渔船。     

金枪鱼延绳钓船机电混合推进系统的应用前景分析

通过分析金枪鱼延绳钓船的作业特点、现有延绳钓船配置及其潜在问题,介绍了电力推进系统的组成、特点和作用,探讨了机电混合推进系统开发的流程和需要注意的问题。归纳出机电混合推进系统具备的优点,包括：可以提高渔船放钓、收钓作业工况下的操纵灵活性,优化主机运行工况、降低故障率,并具有良好的节能减排效果。为渔船升级改造和渔业节能的研究提供参考依据。     

福建省渔业船舶检验人员配置及其管理的探讨

本文根据当前福建省海洋渔业船舶规模和结构现状,分析福建省海洋渔业船舶检验工作、人员配置及其管理中所存在的问题,依据国家渔业船舶检验相关法律、法规的规定,提出强化检验人员配置、加强验船师队伍建设和船舶检验工作管理,提高渔船检验人员整体素质,建立健全检验工作机制,确保渔业船舶航行和生产安全,为船舶建造检验、营运检验营造良好的工作环境等建议,促进福建渔业船舶检验工作健康、有序运行。     

中国海洋捕捞能力的计量与分析

采用数据包络分析方法,以渔船数、总吨位、总功率和专业劳动力为投入指标。以年捕捞产量为产出指标,对我国1994至2005年的近海捕捞与远洋渔业的捕捞能力与能力利用度进行了系统的计量,并以此为依据对我国渔业管理的政策绩效进行了量化分析,发现近年来近海捕捞的渔船数和捕捞劳力的过剩率得到了较好的控制,但渔船总吨位与总功率的过剩率却还处于相对较高的水平。说明目前我国近海增加捕捞能力的主要手段依然是提高渔船的总功率与总吨位,需要在今后的渔业管理中引起重视。通过近海与远洋渔业的比较研究发现,我国近海捕捞能力的实际过剩率已超过了50％,捕捞能力的利用水平不高且提高程度有限;而远洋渔业的能力利用度则尚有较大的提高空间。研究同时显示：我国近海捕捞能力利用度与远洋捕捞能力利用度两条曲线在每次远离后都有互相靠拢的趋势。表明我国远洋捕捞的能力利用度提高后,会吸引近海渔业的部分捕捞能力转入远洋渔业,在降低远洋渔业能力利用度的同时,减轻了近海渔业资源的捕捞压力,也使近海捕捞的能力利用度得以提高;反之,当远洋渔业的能力利用度相对近海渔业较低时,就会有一部分远洋渔业的捕捞能力转入近海捕捞,加大了近海的捕捞强度,使近海捕捞的能力利用度下降。所以,积极提高并保持远洋渔业的能力利用度,对缩减近海捕捞规模有较直接的影响。     

液化天然气渔船改造相关技术分析

为降低渔船燃油能耗,减少渔船污染排放,研究了液化天然气渔船（ LNG渔船）相关技术。 LNG渔船的核心技术在于双燃料发动机动力装置,围绕双燃料发动机动力装置所需空间的利用和布置是LNG渔船改造的一大难点。双燃料发动机动力装置相关配套设备科学合理的设计也是保证LNG渔船高效航行的重要因素。通过对LNG渔船船体改造、双燃料发动机动力装置改造和LNG燃料存储技术等方面进行分析,认为LNG渔船作为一种新型船舶,能有效地降低渔民燃料成本,改善船员作生活环境。     

舟山桁杆拖网渔具渔法分析

桁杆拖虾是20世纪80年代以后迅速发展起来的新兴捕捞作业方式,主要用于开发沿海渔场虾类资源.桁杆拖虾作业方式引进舟山后,迅速成为舟山海洋捕捞业的主要作业方式之一.2013年5-11月通过实地调查,对舟山地区桁杆拖网的捕捞对象、渔具结构、操作方法等进行了分析研究,指出当前舟山桁杆拖虾作业中存在的问题:底杂鱼及蟹类等副渔获物所占比例大,数量和重量占总渔获12.12％和66.58％;使用电脉冲惊虾仪等违法作业仍然存在;网目规格普遍小于国家标准.根据上述问题提出:加装分隔网片,改善网目结构,加大执法力度等相应建议.     

聚酮单丝材料的渔用适配性

聚酮(POK)材料是由一氧化碳、烯烃(乙烯、丙烯)共聚合成的一种工程塑料,有着良好的拉伸性能和优异的抗冲击性能,有望成为一种渔用新材料。为了探究聚酮单丝材料的渔用适配性,本文对POK单丝进行了热性能和动态力学性能测试,又测试分析了其蠕变性能、力学性能和耐磨性能。结果表明：POK单丝的结晶度为38.44%、熔融温度为200.8℃,且使用环境温度可达150℃;与相同直径的超高分子量聚乙烯(UHMWPE)单丝和聚酰胺(PA)单丝相比,同等温度下POK单丝的模量最大(118.04 MPa),且在低温下(0-20°C)具有更优异的力学模量;蠕变试验测得POK单丝的拉伸应变在9%左右,在绳网的长效应用上POK单丝优势明显高于UHMWPE单丝和PA单丝;在结节状态下,POK单丝的结节强力在干(3.96 daN)、湿(4.02 daN)状态下均高于同等直径的UHMWPE单丝和PA单丝;另外,POK单丝的耐磨性能表现优异,在相同摩擦条件下,干(湿)态下POK单丝的强力保持率达58.38%(60.90%),也高于同等直径的UHWMPE单丝和PA单丝。研究表明,与相同直径的UHMWPE单丝和PA单丝相比,POK单丝耐磨、耐高温、高模量、低蠕变、高结节强力,其综合性能和适配性好,这为渔用POK单丝绳索网具的开发及其产业化应用提供了理论和技术支撑。     

秘鲁沿岸秘鲁鳀渔场及渔汛分析

秘鲁鳀(Engraulis ringens)是栖息于东南太平洋沿岸的小型中上层鱼类,了解秘鲁鳀渔场和渔汛的状况有助于渔情预报工作的开展进而实现资源的合理利用。利用2005~2014年秘鲁各港口的上岸量数据,以上岸量(landings)、总捕捞努力量(fishing effort)和单位捕捞努力量渔获量(CPUE)为指标分析秘鲁鳀渔场分布及渔汛;结合二因素方差分析(two-factor analysis of variance)探究渔场月份和纬度上的显著性差异;利用分位数的方法,找出各年的旺汛时间。研究表明,每年的4~6月和11~12月为秘鲁鳀的主汛期;主要的捕捞区域分布在7°S~13°S;渔汛的前中期,上岸量和捕捞努力量有着明显的年间差异,而CPUE在渔汛后期年间差异明显。方差分析表明,不同月份和不同纬度对捕捞努力量[ln(effort+1)]有极显著的影响(P0.01);5月为一年中最主要的捕捞阶段。旺汛期分析表明,第一渔汛阶段的旺汛一般在5月出现,而第二渔汛阶段的旺汛一般在11月出现。研究结果有助于对秘鲁沿岸秘鲁鳀渔场及渔汛的认识。