穿心球塑料浮子制作工艺及焊接夹具的设计

目前我国近海及远洋拖网作业已普遍采和疏目（大目）拖网技术。穿心球形塑料浮子是为了解决大目拖网作业中传统耳环式塑料浮子套挂网衣问题而研制的一种新型拖网属具［１］。可将浮子纲从浮子的中心孔穿过，浮子可绕浮子纲转动，从而可有效避免大目网衣套挂浮子的现象。本...     

φ280mm穿心球形耐压塑料浮子的研制

<正> 一、国内外现状及研制的目的意义 当今世界各国的远洋拖网渔船都在采用网口部分为大网目的拖网和中层拖网作业,传统的耳环式浮子由于容易套挂大网目网衣,甚至造成破网事故。因此,有几个国家研制了一种新型的拖网属具————穿心球形塑料浮子,该浮子去掉传统浮子上的两个系结耳环,浮子纲从浮子中心通孔穿过,这样浮子可以绕浮子纲转动,有效地解决了大网目网衣套挂浮子的问题。现在世界上生产穿心浮     

“柔浮”技术的推广试验

<正> 一、“柔浮”推广的意义渔用柔壁翼型浮子简称“柔浮”,为南海水产研究所渔捞室研制成功的新产品。1982年通过技术鉴定,作为一种新型的拖网水动力浮子。尤其是拖网渔业,产量是鉴定拖网属具优劣的重要标准。而产量又受渔场条件、渔具调整、以及船只与船员捕捞素质等因素所决定。由于“柔浮”具有球形浮子无法比拟的     

拖网内外流速的测试

拖网在曳行中，网内各处和拖网附近的流态与网具的工作情况有密切关系。但是，拖网是由网衣、纲索及其属具构成的柔性体，所以测试拖网区域的流速存在一定困难。     

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。     

基于北斗卫星数据的拖网渔船状态与网次提取

拖网网次是捕捞努力量计算的重要参数,拖网渔船捕捞在放网、拖网、起网过程中速度变化非常明显,北斗船位数按3 min间隔记录渔船的经纬度位置、航速、航向、时间等信息,通过航速可以判断渔船状态。本文对浙嵊渔10201、浙嵊渔10243双拖网调查船的航速进行统计,划分拖网捕捞状态的航速阈值为0.8~1.6m/s,借助北斗船用终端记录的航速,判断渔船状态,提取出全部处于拖网作业的网次,并与现场记录的起放网时间和位置进行了比较验证,放网时人工记录与北斗记录时间差平均为4.3 min,起网时人工记录与北斗记录时间差平均为7.2 min,放网的GPS位置与北斗位置距离差值平均为0.35 nmi,起网的GPS位置与北斗位置距离差值平均为0.24 nmi。     

法国研制双翼帆式浮力装置

这种独特的双翼帆式浮力装置,是在拖网上纲后部的天井网上面装设两层表面涂有聚氯乙烯的织物以代替浮子(类似我国帆张网上的帆布,以下简称帆布).上、下两层帆布的间距是11厘米,下帆布与上纲的间距也是11厘米.它们通过11块垂直的小帆布连接,缝合后的组合形状见图所示.每块小帆布的后伸长度都是30厘米。在上纲为19.7米长     

六片式拖网性能的研究

利用１／７比例的网具模型，在拖曳水槽中对六片式拖网进行水槽试验。得出网口高度公式为：Ｈ＝０．１２１ＣＶ＾－０．８１１。网具阻力公式为：Ｒ＝０．０６９ｄ／ａＬＣＶ＾１．５５９。同时得出力纲上装配浮子能提高网口高度３．６％，上中纲与上纲长度之比不能大于０．１４０，上边纲长度可大于相对应的力纲３．３％等设计网具数据。     

网目尺寸对金枪鱼围网沉降性能及网具形态的影响

根据以往的研究结果和海上网具性能实测,并在听取生产第一线船长意见的基础上,把上海开创远洋渔业有限公司现行金枪鱼围网主网衣下部约三分之一网衣的网目尺寸放大50%,即从260 mm增大到390 mm,以探讨改进围网渔具的沉降性能。实验应用田内准则换算并制作成模型网,在日本下关西日本日网公司专业围网动水槽进行模型试验,比较了侧流、背流、顺流(流速8 cm/s,相当实物网0.20 m/s)3种相对流向的放网模式下放网以及无流(0 cm/s)海况下放网,网目尺寸改变前后围网的沉降性能、网具形态和闭合效果。结果显示,主网衣下部网目尺寸从30 mm (对照网,相当于实物网网目尺寸260 mm)放大到45 mm (试验网,相当于实物网网目尺寸390 mm),网具的沉降深度和沉降速度分别提高1.6%和1.1%;试验网的收绞时间比对照网缩短14.3%,且能保持较好的形态;有流时的3种放网模式下,试验网和对照网浮子纲在放网结束时刻的初始包围面积基本相同;在收绞结束时,试验网浮子纲包围面积为对照网的1.33倍,绞纲结束前6 s,试验网沉子纲包围面积为对照网的1.79倍,说明增大网目尺寸有利于网具包围面积的增大,改善了被围鱼群的活动空间。     

大功率渔船外海拖网模型试验

由于拖网渔具在水中作业，水下观察比较困难，加上拖网网具主要由网线、纲索等材料构成的柔性体，它与刚体不同，在外力的怍用下，极易变形，从而影响作用力。因此，拖网网具形状及其怍用力的相互关系，直接测量或用分析方法推算都是比较困难的。模型试验，     

拖网网目尺寸及其速度效应的探讨

拖网的网目大小(特别是网具前部)对拖速有直接影响，而拖速又对捕捞效率产生重要作用。从理论上说，不但存在着没有渔获效果的临界低速，而且应有一个具有良好渔获效果的最佳拖速．在渔船功率与网具尺度不变的条件下，网目大小的确定应以保证拖网达到最佳拖速为目的。网目可按下式确定：     

Method for estimating buoyancy of midwater float required to standardize hook depth in pelagic longline

ABSTRACT:   A midwater float is a small float attached to the mainline of pelagic longlines to standardize the hook depth. In this study theoretical equations are presented for estimating the buoyancy of the midwater float required to lift the joints of the midwater float line on the mainline to the target depth. Sea trials using full scale tuna longline gear with midwater floats were carried out in the Indian Ocean in December 2004 and 2005, in order to examine the validity of the theoretical equations. In the sea trials, two types of midwater float settings, single midwater float setting and double midwater float setting, were tested and compared with the conventional setting. As a result, the joints of the midwater float line on the mainline were successfully lifted to the target depth as expected, demonstrating the validity of the theoretical equation. The range of hook depths in the midwater float setting was less spread over depths than in the conventional setting, and therefore, use of long float lines (100 m) with the midwater float setting allows all hooks to avoid entering the sea turtle habitat of shallower than 100 m depth. Factors affecting shoaling of the longline with the midwater float are also discussed.     

应用两种不同的波浪理论计算方形网箱水平波浪力

运用莫里森(Morison)和库兹涅佐夫(Kuznetsov)的计算方法对方形网箱及其构件受到的水平波浪力特性进行分析,分别依据正弦波和司托克斯二阶波理论,导出相应水平波浪力的迭加计算公式,并把计算结果与两种尺寸的网箱水槽试验进行对比验证。结果显示,正弦波理论计算值与试验值平均误差分别为11．19％和13．67％,二阶波计算平均误差分别为11．03％和13．87％,表明两者计算结论的差异性和计算方法的可行性。在波长、周期、波高和水深分别为150m、10．2s、10m、40m情况下模拟计算实物网箱水平波浪力,其二阶波受力峰值范围比正弦波的要窄、波谷值曲线要平坦,两者波浪力计算相差达8．70％,并且相差率与波高、波长成正比例关系,与水深成反比例关系,从而说明不同的波浪水域环境下应用不同波浪理论计算具有重要意义。     

Aerial drone technology can assist compliance of trap fisheries

Illegal fishing is a global issue that threatens the viability of fishing industries and biodiversity conservation. Management agencies typically use on‐ground surveillance to monitor and minimise illegal fishing practices, the efficacy of which may be enhanced by integrating emerging remote sensing technology. Affordable drones may contribute to cost‐effective detection of illegal fishing activity and associated gear, although their application has yet to be evaluated in many types of fisheries. Here, the utility of drones for the detection of crab traps and floats set in a shallow estuary was quantitatively tested, and the effects of survey altitudes, cameras and monitor screens on detection rates were determined. It was found that drone flight altitude and float colour influenced the detection rates of common crab trap floats, with infrared cameras improving the detection of floats camouflaged by black paint. However, the type of monitor screen used by the drone operator had no influence on the detection of crab traps. Overall, it appears drones can contribute to cost‐effective compliance in estuarine trap fisheries, and the approach can contribute to evidence‐based standard operating procedures.     

Mitigating sea turtle by-catch in coastal passive net fisheries

There is growing evidence that small-scale, coastal, passive net fisheries may be the largest single threat to some sea turtle populations. We review assessments of turtle interactions in these fisheries, and experiments on gear-technology approaches (modifying gear designs, materials and fishing methods) to mitigate turtle by-catch, available from a small number of studies and fisheries. Additional assessments are needed to improve the limited understanding of the relative degree of risk coastal net fisheries pose to turtle populations, to prioritize limited conservation resources and identify suitable mitigation opportunities. Whether gear technology provides effective and commercially viable solutions, alone or in combination with other approaches, is not well-understood. Fishery-specific assessments and trials are needed, as differences between fisheries, including in gear designs; turtle and target species, sizes and abundance; socioeconomic context; and practicality affect efficacy and suitability of by-catch mitigation methods. Promising gear-technology approaches for gillnets and trammel nets include: increasing gear visibility to turtles but not target species, through illumination and line materials; reducing net vertical height; increasing tiedown length or eliminating tiedowns; incorporating shark-shaped silhouettes; and modifying float characteristics, the number of floats or eliminating floats. Promising gear-technology approaches for pound nets and other trap gear include: replacing mesh with ropes in the upper portion of leaders; incorporating a turtle releasing device into traps; modifying the shape of the trap roof to direct turtles towards the location of an escapement device; using an open trap; and incorporating a device to prevent sea turtle entrance into traps.     

对印度尼西亚海域中国渔船使用拖网渔具的分析和探讨

本文探讨了中国渔船在印度尼西亚海域使用的拖网渔具,从渔具使用规格、缩结状态和结构等方面进行了分析,指出这类渔具在浅水渔场捕捞带鱼时有良好适应性,但局部配纲不当,网具贴底程度未达到最佳状态。由于网目大,有些局部改革可能导致敏感的负面反应。作者认为,这类网具今后的改革应着眼于提高拖速,以增加对某些优质鱼的兼捕比例。     

一种水质监测机器人取水装置设计

针对移动水质监测机器人取水深度不够的问题,设计了一种屈伸臂取水装置。采用刚性结构屈伸臂保证取水水位准确性,应用丝杠滑块结构构成伸缩采样机构,通过控制系统控制各模块协调工作实现取水过程。控制系统基于无线遥控原理设计,完成了对取水流程及基础运动控制。     

A numerical study of inferred rockfish (Sebastes spp.) larval dispersal along the central California coast

Successful recruitment of marine fishes depends on survival during early life-history stages, which is influenced by oceanic advection due to its impact on coastal trophodynamics and transport processes. Here we evaluate the influence of ocean circulation on the dispersal of rockfish ( Sebastes spp.) larvae along the central California coast using an implementation of the Regional Ocean Modeling System, driven at the surface by output from the Coupled Ocean Atmosphere Mesoscale Prediction System. Thousands of floats simulating rockfish larval propagules, constrained to follow fixed depths, were released over a broad coastal area at 2-day intervals, and transported by simulated ocean currents at depths of 1, 7, 20, 40, and 70 m. Trajectory statistics are averaged across the 4-yr period from January 2000 through December 2003 to reveal mean trajectory direction, net displacement, fractional cross-shore loss, and duration of retention for different seasons. On average, near-surface propagules originating nearshore are transported offshore during the upwelling season, whereas deeper propagules move alongshore to the north. This vertical shear vanishes during winter, with most floats moving alongshore to the north, regardless of depth. After 35 days in the water column, typical transport distances were ∼50 km for floats remaining nearshore and ∼150 km for floats over the midshelf and slope. Implications for performance of marine reserves for rockfish conservation are discussed. Our results also provide evidence for a strong semiannual pattern of coastal retention rates, with high export of near-surface drifters during the upwelling season. In contrast, high rates of shelf retention occurred for releases at 20 m and deeper during summer, and at all depths during winter.