A new algorithm for estimating gillnet selectivity

The estimation of gear selectivity is a critical issue in fishery stock assessment and management. Several methods have been developed for estimating gillnet selectivity, but they all have their limitations, such as inappropriate objective function in data fitting, lack of unique estimates due to the difficulty in finding global minima in minimization, biased estimates due to outliers, and estimations of selectivity being influenced by the predetermined selectivity functions. In this study, we develop a new algorithm that can overcome the above-mentioned problems in estimating the gillnet selectivity. The proposed algorithms include minimizing the sum of squared vertical distances between two adjacent points and minimizing the weighted sum of squared vertical distances between two adjacent points in the presence of outliers. According to the estimated gillnet selectivity curve, the selectivity function can also be determined. This study suggests that the proposed algorithm is not sensitive to outliers in selectivity data and improves on the previous methods in estimating gillnet selectivity and relative population density of fish when a gillnet is used as a sampling tool. We suggest the proposed approach be used in estimating gillnet selectivity.     

混凝土船形鱼礁的礁体设计与沉降计算

根据人工鱼礁礁体设计的基本理论和原则,考虑实地投放条件和投放要求,对船形混凝土人工鱼礁进行结构设计和沉降计算。计算得到礁体的横稳心高度(?)约为0.56 m,满足一般船舶在海面的稳性设计要求;船形礁于海面4 kn拖速下所受拖曳阻力R_F值为318.04 N;礁体在水深30 m海域投放,最终速度为2.49 m/s,沉降时间13.41 s;通过计算礁体着底时的底冲力为150.00 kN,换算得出鱼礁结构强度均布荷重q(213.78 kN/m),为礁体建造时的强度要求提供依据。     

我国金枪鱼围网渔业的初步研究

报道2002年6月至2003年5月两艘围网渔船在中西太平洋围捕金枪鱼及每月作业状况。结果显示,70%的网次围捕浮水鱼群,其空网率达52.5%,30%的网次围捕流木鱼群,其空网率为9.5%;渔获物中鲣鱼(Katsuwonuspelamis)占90%,优势体长为40～60cm,黄鳍金枪鱼(Thunnasalbacares)占10%左右,优势体长为100～150cm;作业渔场位于5°N～5°S,137°E～178°E;两艘船每月的空网率为9%～64%,每月渔获量在185～940t之间波动,平均有效网次产量不低于20t,最大网次产量为260t。     

中国沿海围网技术参数的分析和比较

本文对中国沿海几十种围网的技术参数进行了分析和比较。     

威海小石岛人工鱼礁海域渔获物群落结构特征及其与环境因子相关性

为探究人工鱼礁投放对威海小石岛附近海域渔获物种类组成、渔获量变化、渔获物结构特征的影响,作者于2012~2013年对威海小石岛人工鱼礁区及对照区的渔获物和环境因子进行了调查,并采用聚类分析、单因子相似性分析及相似性百分比分析对渔获物结构特征进行分析,采用典范对应分析(CCA)对礁区主要物种与环境因子的相关性进行分析。结果显示,南、北礁区地笼网调查到渔获物种类数量高于对照区,分别为24、31和18种。南、北礁区鱼类和甲壳类生物资源量高于对照区。南、北礁区全年资源量占优势的种类为日本蟳(Charybdis japonica)和大泷六线鱼(Hexagrammos otakii),对照区为海刺猬(Glyptocidaris crenularis)和大泷六线鱼。聚类分析和单因子相似性分析表明,渔获物组成结构在季节间差异显著(P0.05),在春季和夏季,人工鱼礁区渔获物组成结构和对照区差异显著(P0.05)。典范对应分析表明,水温、叶绿素a和溶解氧是影响礁区主要渔获物种类分布的主要环境因子。投放人工鱼礁改善了威海小石岛礁区水域的渔获物群落结构,并增加主要鱼类、甲壳类经济物种的渔获量。     

Characteristics from a hydrodynamic model of a trapezoidal artificial reef

Flume experiments and numerical simulation were conducted to characterize the hydrodynamics of a trapezoid artificial reef. Measurements in particle image velocimetry were conducted to observe the formation of upwelling and vortices; and forces for the reef model were measured by load cell. The results of flume experiments agree well with the numerical data. In addition, the flow structure around a reef combining trapezoidal and cubic blocks was simulated numerically under two deployment schemes, showing a more complicated flow structure than that of a stand-alone reef. Relationship between drag coefficient and Reynolds number suggest that the degree of turbulence can be assessed from the value of drag coefficient downstream from the reef. The role of the reef in water flow is to reduce flow velocity and generate turbulence.     

日本花鲈细胞色素b基因部分序列的研究

首次报道日本花鲈线粒体ＤＮＡ细胞色素ｂ基因片段的ＰＣＲ扩增及其序列测定。得到４１０ｂｐ的碱基序列,其Ａ、Ｔ、Ｇ、Ｃ含量分别为９９ｂｐ（２４．１５％）、１１３ｂｐ（２７．５６％）、７２ｂｐ（１７．５６％）、１２６ｂｐ（３０．７３％）,与其他鱼类相同基因片段碱基序列含量相似。     

人工鱼礁增殖金乌贼资源研究进展

金乌贼（Sepia esculenta Hoyle）是中国北方沿海重要的经济头足类,主要渔场在山东沿海,以日照岚山至青岛胶州湾一带最多,向北依次递减,进入渤海数量极少^[1]。     

不同内倾角海螺笼对脉红螺的诱捕效果

作者对不同内倾角海螺笼对脉红螺(Rapana venosa)的诱捕效果进行了实验研究。在实验室水槽中,观察了4种不同内倾角(35°、45°、55°和65°)的海螺笼对脉红螺的诱捕效果,同时还研究了光照和温度对海螺笼诱捕效果的影响,为优化海螺笼捕捞技术提供理论依据。实验结果表明:在相同的实验条件下,不同的内倾角对海螺笼诱捕效果影响十分显著(P<0.01),其中内倾角为45°的海螺笼诱捕效果最好,内倾角为35°和55°的海螺笼较好,而内倾角为65°的海螺笼诱捕效果则最差。同时发现,内倾角对脉红螺的个体大小具有选择性,随着内倾角的增大,壳高<7cm的个体占相应笼诱捕总数的百分比越来越小。光照对海螺笼的捕捞效果有十分显著的影响,而温度的影响则不明显。     

渔具合成纤维材料强度性能的比较与分析

渔用合成纤维及其网线和绳索是构成渔具的基本要素，其强度性能对渔具的力学性能、渔获性能、使用寿命和制造成本具有重要作用。为了满足海洋渔业不断发展的需要，我国陆续颁布了一批国家及行业质量标准，并在实践中逐步接近ＩＳＯ标准或国际名牌产品标准，使渔具纤维材料性能有了较大的提高。本文通过对国内外渔具合成纤维材料强度性能的比较和分析，认为：（１）国产合成纤维长丝的有关性能与日本产品无显著差异；（２）国产ＰＡ胶丝性能普遍较好，并优于英国产品，而ＰＡ长丝捻线与国外产品尚有较大差距；（３）ＰＥ线产品性能普遍超过ＱＪ／ＣＮＦＣ０２９２标准，但仍低于ＳＣ１４１—８５标准要求；（４）国产ＰＡ长丝三股绳索性能与德国产品接近而高于日本产品；（５）ＰＥ和ＰＶＡ三股绳索性能仅略高于日本产品；（６）渔具新材料的研制及其在渔业中的开发应用与国外相比，尚有较大差距，应得到足够重视。