441千瓦双船底拖网网口高度与网口周长的关系

本文报道了１９８６￣１９９２年期间对４４１ｋＷ渔船使用的１顶度拖网网口高度的海上实测结果。结果表明：网口高度是网口拉直周长的５．５￣７．３％。两者的关系可用经验公式表示为：Ｈ＝０．２６０９Ｌ＾０．７３４４。     

四片式中层拖网主要部件尺寸变化对其性能的影响

通过拖网系列模型水池试验，研究四片式中层拖网网衣主要部件尺寸变化对网具性能的影响，试验结果表明：（１）因侧网宽度变化对扫海面积影响的规律是侧网密度越小，扫海面积越大，在拖速３．５￣５．０ｋｎｏｔ的范围内，扫海面积随着网袖长度的增长而增大；当其比值大于３０．９３６％以后，扫海面积随着网袖长度的增长而减小，网袖长度对网具阻力影响的趋势是网袖长度越长网具阻力越大，（３）网身长度与网口拉直长度之比为２５．     

淤泥湖近太湖新银鱼的生长研究

对生活在湖北淤泥湖中的近太湖新银鱼进行了生长研究。结果为：①全长与体重的相关关系：Ｗ＝２．３１２×１０＾－６Ｌ＾３．００；②全长生长方程：Ｌｔ＝７２．３（１－ｅ＾－０．３（ｔ＾－０．１）），体重生长方程Ｗｔ＝０．８７３８（１－ｅ＾－０．３（ｔ＾－０．１））＾３。③Ｌ∞＝７２．３（ｍｍ），Ｗ∞＝０．８７３８（ｇ），ｋ＝０．３ｔ＝０．１，拐点年龄ｔｉ＝３．７月龄，拐点体重Ｗｉ＝０．２５ｇ。     

扩张帆布对大型中层拖网性能的影响

针对我国引进的大型中层拖网所使用的扩张帆布,通过拖网模型试验,设计了三种面积和三种不同冲角的扩张帆布调整试验,并比较了使用扩张帆布与使用塑料浮子对网具性能的影响。结果表明：网口拉紧长度1040m,网口网目为a=20m六角形网目的大型中层拖网,使用长度为100m手纲、长度为48m叉纲、重锤重量为320kg×2、下袖端间距68．4m时,在帆布面积调整试验中,当冲角前纲长度为17．2m,冲角后纲长度为17．6m,拖速为2．57m·s^-1条件下,使用5．0m^2的扩张帆布比4．0m^2网口高度可提高11．92％,网具阻力上升6．74％,能耗系数下降6．5％。在冲角调整试验中,使用5．0m^2的扩张帆布,当冲角后纲的长度固定为17．6m,冲角前纲的长度从17．2m缩短为16．4m时,网口高度下降26．36％,网具阻力下降11．22％,能耗系数上升24．1％。大型中层拖网使用扩张帆布比使用塑料浮子在不同的拖速下网口高度变化幅度小,在高拖速时,有网口高、能耗系数低的优势,但在拖速低于2．06m·s^-1时,网口垂直扩张和能耗系数没有优势。试验的长宽比为20的扩张帆布的升力系数Cy可达1．16左右。     

太仓浮桥拖网网具性能初探

本文报道了使用斯玛捞作业监控仪对太仓浮桥拖网海上作业实测结果，在拖速３．３－３．９节条件下，该网浮拖作业网口高度为１１．７－１３．８米，底拖作业网口高度１１．８米。分析讨论了在投放不同曳纲长度时，椭圆形网口形状和变化趋势，其长，短轴之比浮拖作业为０．５１，底拖作业为０．４６。     

网湖鲤鱼生长的研究

研究了网湖鲤鱼的生长特性。体长与鳞径的关系为Ｌ－４．７４０２Ｓ－４．０１９４。体长与体重的关系为Ｗ＝０．０１１２Ｌ＾３．１８０．用ＶｏｎＢｅｒｔａｌａｎｆｆｙ生长方程表达网湖鲤鱼体长、体重与年龄的关系：Ｌｔ－７５．１６［１－１＾－０．１７２９（ｔ＋０８０２９）］，Ｗｔ＝１１０７７．３１［１－１＾０．１７２９（ｔ＋０．８０２９］＾３．１９８０。拐点年龄为ｔｉ＝ｔ．５５齿，拐点体长Ｌｉ＝５０．１０ｃｍ     

帆式张网扩张帆布与网具性能的研究

通过对帆式张网模型水池试验,研究了扩张帆布对帆式张网网具性能的影响。结果表明：（１）扩张帆布冲角表征值为１６１～１７４°时,网具阻力较小,网口垂直扩张和水平扩张较大,网具性能较好;随着冲角表征值的变大,网具性能有所下降。（２）帆式张网网口垂直扩张随扩张帆布高度增加而变高,随流速的加大而增高幅度有所减小。（３）抽取中间３块扩张帆布（５ｍ×３）,帆布扩张力明显不足;当流速小于２０ｋｎ时,抽取中间１块比抽取最后第２块网具性能更好。（４）当流速从１０～３５ｋｎ时,经增加２根扩张帆布的撑杆后,网口垂直扩张略有增加,增加幅度为１６％～２２％;水平扩张随流速的增加扩张性能提高明显,增加幅度为２５％～１２２％。     

高效鱼虫灭对鱼类等淡水生物的急性毒性及杀虫试验

“高效鱼虫灭”对草鱼，白鲢越冬鱼种４８－７２ｈ的Ｔｌｍ分别为２．５、２．３３ｍｌ／ｍ＾３，安全浓度分别为０．７５、０．６９９ｍｌ／ｍ＾３；对草鱼，白鲢越冬鱼种７２ｈ的最低致死浓度均为０．５－１ｍｌ／ｍ＾３，致死率分别为２０％、２５％；对鳙鱼越冬鱼种的最低致死浓度大于３ｍｌ／ｍ＾３；青虾，淡水白鲳、枝角类对高效鱼虫灭敏感。     

五种鱼药对河蟹的毒性试验

中华绒螯对强杀虫灵的９６ｈＴＬＭ植为３．５ｇ／ｍ＾３，安全浓度为０．３５ｇ／ｍ＾３，在０．１ｇ／ｍ＾３灭虫精溶液中９６ｈ未死亡，但有急性中毒反应；在１．０ｇ／ｍ＾３，１．２ｇ／ｍ＾３，１．４ｇ／ｍ＾３硫酸铜溶液中，蟹种虽能蜕壳，但蜕壳后４～８ｈ即死亡，在０．０９ｍｌ／ｍ＾３２０％杀灭菊酯９６ｈ未出现异常及死亡现象；在１．７５ｇ／ｍ＾３菊乐合酯中９６ｈ表现正常。     

二氧化氯改善养殖水环境效果的研究

使用二氧化氯化处理水养殖用水（实验室规模）测定水化学指标及水中细菌数量的变动,结果表明：（１）二氧化氯能够明显中水环境的溶氧（增氧量为５．８－２２．７％）减低水中ＣＯＤ和ＮＨ３－Ｎ值（ＣＯＤ降低幅度为２６．０－５８．８％,ＮＨ３－Ｎ清除率为１９．４－３８．５％）（２）二氧化氯浓度为０．２×１０＾－３ｍｏｌ／ｍ＾３及１．２×１０＾－３ｍｏｌ／ｍ＾３可有显降低海水中弧菌数及细菌总数,随着药物浓度增大,     

绳拖网网口结构设计和装配工艺

本文主要阐述适用于我国东海和黄海渔场的双船两片式底层绳拖网网口结构设计，上、下纲和悬纲长度计算方法及其装配工艺。根据绳拖网的上纲和下纲的工况特点，上纲呈抛物线状；下纲呈悬链线状，分别依据其各自的曲线方程组求算。关于悬纲和上、下纲之间的装配工艺，是按我国底层拖网特点设计的。经生产实践，证实这些设计和装配都是合适的。     

底拖网配纲校核法

在分析比较目前中国各地曾使用过的各种底拖网配纲校核方法的基础上，提出了“网翼上、下边缘配纲之差与网盖缩结长度之比”（简称翼纲差比）的新配纲校核方法。翼纲差比较大的拖网，其网口易于升高而沉纲贴底程度较小些；反之，翼纲差比较小的拖网，其网口不易升高而沉纲贴底程度较大些。     

大网目底中层拖网模型试验研究

利用1:22.82比例的2张网具模型,在拖曳水槽中进行底中层拖网的网具性能测试,得出网具阻力公式为:F=0.121(d/a)LCV~(1.62),网口高度的公式为:H=0.225CV~(-1.316),2张网具的作业性能良好,GM_2的垂直张开性能优良,拖速3节时的垂直扩张系数已接近7％,能耗系数在拖速3节时为0.2kw.h/10~4m~3,在同类渔具中较优;GM_1网的能耗系数比GM_2网低,在拖速3节时低于9％左右,作为中层拖网时的总体性能优良。     

Harbour swimming nets: a novel habitat for seahorses

• 1. Artificial structures are becoming increasingly important in conserving biodiversity in urban ecosystems, by providing habitat for endangered or rare species. Their role in providing habitat for such species has, however, been largely unexplored.
• 2. In Sydney Harbour, Australia, seahorses were observed among the netting used to keep sharks out of swimming enclosures. Over a 2‐year period, the relative densities of two species of seahorses observed on netting was measured at swimming enclosures with permanent netting and at swimming areas that were only enclosed with netting during the summer months.
• 3. The rate of colonization by seahorses to new netting was also examined over a period of 10 months.
• 4. Numbers of seahorses on permanent swimming enclosures were 10 to 100 times greater than numbers present on swimming enclosures that were only set up during the summer months.
• 5. This large difference may have been attributed to the slow rate of colonization of seahorses to new habitat. Seahorses were not observed at experimental nets that were deployed in two areas in the harbour until at least 4 months after the netting was deployed.
• 6. Swimming pool nets are a habitat for species of seahorses in Sydney Harbour and, consequently, the removal or disturbance of swimming nets may impact the survival of these fish. Management of these artificial habitats may therefore best be focused on providing a permanent habitat that may help to compensate for the loss of netting during winter months.

Copyright © 2007 John Wiley & Sons, Ltd.     

Biofouling of salmon cage netting and the efficacy of a typical copper-based antifoulant

With the relatively recent advent of intensive aquaculture practices, there is a need for data on the contemporary biofouling and antifoulants associated with it. Therefore, experiments were conducted to yield data on the biological communities that develop on contemporary fish cage netting, both antifouled and untreated. The efficacy of a typical copper-based antifouling treatment was assessed through netting immersion trials performed at a salmon farm site in Clift Sound, Shetland. Over a 10-month period, regular samples were taken and data generated on the fouling biomass and species composition of the communities that developed. Furthermore, percentage net aperture occlusion values (PNO) were calculated with the aid of an image capture and analysis system, which is a methodology that shows excellent potential for use in future net fouling trials. Over the course of the trial, PNO values calculated from control netting rose quickly, but remained low for 150 days longer on treated nets; by day 210, PNO values were 98.72% and 3.06% for control and copper nets, respectively, immersed at 3 m. Following 10 months immersion, treated nets significantly reduced the biomass accumulation of biofouling compared to control nets (1.8 kg m^− 2 as opposed to 4.9 kg m^− 2). A total of 40 separate taxa were identified during the study, and species richness and composition data were significantly affected by the application of copper-based antifouling; for example, average species richness values were 16 and 9.75 for control and copper nets, respectively, immersed at 1 m. Of significance, the species Mytilus edulis and members of the Ascidiacea, including Ciona intestinalis and Ascidiella aspersa, were observed fouling the copper-treated netting.     

Sampling fish assemblages in forested floodplain wetlands

Abstract– Four quantitative (area-standardized electrofishing, trap nets, small-mesh [1.3 and 2-cm bar mesh] gill nets, large-mesh [2.5 and 5-cm bar mesh] gill nets) and two qualitative (non-standardized electrofishing, dip netting) sampling techniques were concurrently used to capture larval to adult fish in forested wetland habitats on seasonally inundated floodplains of two Alabama (USA) streams. Standardized area electrofishing appeared to be the best sampling technique for collecting and quantifying species because of high catch rate, broad species and size coverage, and rapid sampling. Electrofishing accounted for most fish (47 and 57% of pooled catch), almost all taxa, and a broad range of fish sizes. Large-mesh gill nets captured few fish (2% and 8%), a distinct subset of the species present, and the largest fish. Light traps were the most efficient and taxa-comprehensive sampling technique for larval fish. Light traps captured the vast majority of the pooled larval fish catch, including 6 of 7 families recorded at the sites. Larval fish dip netting captured larval fish of most families known to be present but in low numbers. For surveys of species composition and rapid bioassessments, nonstandardized electrofishing and larval fish dip netting appear adequate. For intensive research studies, the combination of area electrofishing, large-mesh (and in some cases small-mesh) gill nets, and light traps provide thorough and comprehensive data on wetland fish assemblages.     

Engineering procedures for design and analysis of submersible fish cages with copper netting for exposed marine environment

Novel design and analysis procedures are needed for engineering of the offshore fish farms utilizing copper alloy netting. Existing technologies developed for fish cages with polymer nets are not directly transferrable to the fish cages with copper netting. In particular, the structural integrity of fish cage/mooring systems, and initial high costs of fish cages with copper netting are two major concerns in the engineering for open ocean aquaculture. We propose the modified engineering procedures, which address these concerns and allow for retrofitting of existing fish farming systems with polymer nets. These procedures are illustrated by considering two case studies: design of a rigid-frame and flexible gravity-type fish cages. Performance of both designs is analyzed after the field trials in the North Atlantic and South Pacific oceans, correspondingly.     

The use of fyke nets as a quantitative capture technique for freshwater eels (Anguilla spp.) in rivers

Abstract  Fyke netting is a convenient and effective technique for capturing freshwater eels, and catch-per-unit-effort is usually assumed to be an index of eel abundance. The present study investigated the potential of depletion fishing using baited fyke nets to obtain population estimates of longfin eels Anguilla dieffenbachii Gray, in a river in the South Island of New Zealand. The probability of capture (capture efficiency) of a single night's fishing increased with increasing size of eel, and ranged from 0.2 to 0.9 for eels <400 mm, to 0.7–0.9 for eels ≥500 mm. The capture efficiency of baited vs unbaited nets was assessed in a small stream that was electric fished after netting trials were completed. Baited nets proved to be an effective method of assessing abundance of longfin eels (>400 mm) but not shortfins ( A. australis Richardson); capture efficiency of the population of longfins (the sum of fyke caught and electric fished eels) was 0.4 for a single night's fyke netting, increasing to 0.8 over four nights. Comparable efficiencies for shortfins were <0.1 and 0.3 respectively. Unbaited nets were markedly less efficient for both species.     

中国沿海刺网网具遗失率影响因子

为掌握影响我国沿海刺网渔船网具遗失率(R_G)的因子及其程度,对中国沿海渔民开展了问卷调查。利用调查数据,结合GAM模型分析了影响我国刺网渔船网具遗失率的因子及其程度。结果显示:(1)影响我国沿海刺网渔船网具遗失率的因子(解释偏差)分别为单航次天数(86.8%)、年作业天数(4.2%)、单航次渔具携带重量(2.8%)、作业水深(2.4%)、渔船吨位(0.9%)和年均渔具采购数量(0.1%);(2)GAM模型能用于研究渔船网具遗失率和影响因子之间的关系;(3)随着单航次天数和年作业天数的增加,R_G呈上升的趋势;(4)随着作业水深的增加、单航次渔具携带重量超过18 000 kg时,R_G呈下降趋势。建议采取以下措施以降低刺网渔船网具遗失率:(1)单航次天数不得超过30 d,减少年作业天数;(2)根据渔船的吨位,确保网具单航次携带重量在18 000 kg以上;(3)根据刺网渔具的高度规定作业水深和作业渔区;(4)渔船总吨位控制在200 t以内。     

Experimental study on the effect of horizontal waves on netting panels

The effect of horizontal waves on flexible netting panels is examined in this study, to evaluate the testing method of pretensioned mooring, radial systems, and flexible netting structures. The netting was suspended at a specific hanging ratio for six polyethylene panels with different characteristics. The aim was to evaluate the calculation method for horizontal wave forces on flexible netting panels. A regular wave was used in the experiment, with wave period 0.8–2.0 s and wave height 50–250 mm. The force on the netting structure was recorded by a tension transducer and digital signal recorder, and was simulated by a cubic spline in terms of the wave experiment under different wave conditions. The horizontal wave force on the netting panel changed periodically and asymmetrically, which was similar to the surface wave elevation. The horizontal wave force was related to the netting panel height and width (l), wave height (H) and wave length (L), twine diameter (d) and bar length (a) of the mesh. Using dual series relations, least-squares approximation, and multiple stepwise regression analysis, the following formula was obtained for the horizontal wave average apex value (F) on the netting panel: F=0.13ρgl(H/2)²(d/a)(H ^0.64 L ^0.77/0.9a ^0.44).