大西洋金枪鱼延绳钓主要渔获种类及其分布

根据收集的有关文献和海上调查资料，分析了大西洋金枪鱼延绳钓生产的主要渔获品种的生物学特性、捕捞生产情况及管理措施等。此外，还根据FAO建立的金枪鱼生产数据库，采用GIS软件制作了大西洋金枪鱼延绳钓主要渔获种类捕捞产量的地理空间分布图。并分析了其资源的空间分布特征。     

太平洋大眼金枪鱼延绳钓渔获分布及渔场环境浅析

本文主要根据收集到的渔获量数据、海水表层温度数据和有关文献资料 ,应用GIS技术对太平洋大眼金枪鱼延绳钓渔业进行了定量或定性分析。结果表明 :太平洋大眼金枪鱼延绳钓渔场主要分布在 2 0°N～2 0°S之间的热带海域 ,具纬向分布特征。对渔获产量同海表温度的分月统计显示 :太平洋大眼金枪鱼渔场最适月平均表层水温约 2 8～ 2 9℃ ,渔场出现频次为偏态分布型。最后 ,结合有关文献综合讨论分析了海表温度、溶解氧含量、海流等环境因子与金枪鱼渔场分布和形成机制的关系     

印度洋金枪鱼延绳钓主要渔获种类及分布

根据印度洋金枪鱼管理委员会IOTC的金枪鱼生产数据库,对1967-2004年间印度洋金枪鱼延绳钓主要渔获种类的产量按年进行汇总和基于5度格网进行了空间上的统计,采用GIS软件制作了印度洋金枪鱼延绳钓主要渔获种类的捕捞产量的地理空间分布图,分析了其资源的空间分布特征。分析结果表明,大眼金枪鱼Thunnus obesus、黄鳍金枪鱼Thunnus albacares、长鳍金枪鱼Thun-nus alalunga和剑鱼Xiphias gladius是印度洋金枪鱼延绳钓的主要渔获种类,其产量之和占到总产量的90%,这4种印度洋金枪鱼延绳钓的主要渔获种类从1967-2004年的产量均呈上升趋势,但产量的峰谷变化各不相同;空间分布特征研究表明,尽管在印度洋海域分布范围广泛,但产量丰沛的区域存在明显差异。     

印度洋大眼金枪鱼延绳钓适宜渔获环境的初步研究

数值分析得出大眼金枪鱼的渔获适宜环境参数值范围：温度14～17℃,盐度34．5～35．4．溶解氧浓度1．5～4．5mg／L,温跃层深度80～160m,营养盐氮、磷、硅浓度分别大于12-μg／L,09μg／L,14μg／L。聚类分析表明,钓获率与营养盐关系最为密切。另外,通过因子分析,深化了对钓获率和渔获环境因子两者间关系的理解。     

大西洋中部金枪鱼延绳钓性能评估初步研究

利用2009～2010年我国大西洋中部金枪鱼延绳钓调查数据,对金枪鱼延绳钓钓具性能进行评估。结果表明:金枪鱼延绳钓具有较好的种类选择性,大眼金枪鱼渔获量和尾数分别占总渔获量的73.67%和76.00%;大眼金枪鱼(Thunnus obesus)、黄鳍金枪鱼(Thunnus albacares)和剑鱼(Xiphias gladius)未达到性成熟的渔获尾数比例分别为13.00%、25.97%和48.93%;1～6号钓钩,大眼金枪鱼上钩率随钓钩深度增加呈递增趋势,6～8号钓钩上钩率呈递减趋势,6号钓钩上钩率最大为9.46尾/千钩;3号至8号钓钩上钩率均大于7尾/千钩,表明1号和2号钓钩利用率偏低;根据钓钩理论深度,推测大眼金枪鱼主要分布水层为220m～350m。通过调节缩短率和浮子绳长度对钓具进行优化,使得钓钩分布水层与大眼金枪鱼分布水层更为接近,提高钓钩利用率。     

热带大西洋金枪鱼延绳钓兼捕鲨鱼种类组成和渔获率及其与表温的关系

根据2007年12月~2008年3月采集的热带大西洋(05°37′~12°01′N、29°00′~36°51′W)金枪鱼延绳钓渔获物数据,分析了金枪鱼延绳钓兼捕鲨鱼的种类组成、渔获量、渔获率及其与表温的关系。本次调查共捕获鲨鱼8种,隶属3目7科7属,总渔获尾数为633 ind,总渔获量达26 837.4 kg,其中大青鲨为主要兼捕种类。各种鲨鱼渔获率平均值在0.003~1.524 ind/1 000 hooks之间,其中大青鲨最高,其值为1.524 ind/1 000 hooks,大眼砂锥齿鲨最低,其值为0.003 ind/1 000 hooks。各种鲨鱼渔获率月变化不明显(ANOVA,P=0.901)。鲨鱼总渔获率和大青鲨渔获率与表温都呈显著性负相关。大青鲨主要出现渔场的表温范围为24.6~25.8℃。     

金枪鱼延绳钓力学性能研究进展

延绳钓的力学性能直接影响渔获效率与能源消耗。文章总结了国内外金枪鱼延绳钓力学性能由最初的海上实测到动水槽模型试验再到数值模拟研究的相关研究方法与成果。结果显示:1)延绳钓的力学分析已从静态分析发展为动态分析;2)进行小尺度延绳钓模型试验,目的是验证特定情况下数值模拟分析的准确性;3)根据数值模拟和实测结果确定了延绳钓干线垂直阻力系数(CN90)为1.12和惯性力系数(Cm)为3。建议今后对延绳钓力学性能研究为:1)研究渔具材料刚度、阻尼对数值模拟精度的影响;2)结合金枪鱼的行为特征研究其上钩后的水动力,并将其考虑到模型之中,使模型与实际作业状态更加接近;3)对于渔具与海流、渔船、绞机和渔获物之间的相互作用机理进行深入的数值模拟研究。     

太平洋金枪鱼延绳钓渔业

本文主要介绍了最近几年太平洋金枪鱼延绳钓渔业的发展情况和太平洋沿岸国家金枪鱼延绳钓生产现状,重点叙说了太平洋金枪鱼延绳钓捕捞的几个主要种类的渔场分布、产量变化动态和发展趋势,为我国远洋渔业单位进行金枪鱼延绳钓开发提供参考。     

热带大西洋公海金枪鱼延绳钓渔获物上钩率的分析

报道 1 994年 1 1月至 1 996年 1 0月 (4～ 7月除外 )金丰 2号延绳钓船在中部大西洋公海 (0 9°N～ 0 5°S ,1 8°W～ 34°W )钓捕渔获物和各月经济鱼种上钩率的状况。经过鉴定共有 2 7种鱼类和一种海龟。在 2月的北纬渔场和 1 2月上半月在南纬西部渔场 (0 1°S～ 0 5°S ,2 4°W以西 ) ,大眼金枪鱼的上钩率达到高峰值 ,均大于 8‰ ,其它期间在钓捕海域上钩率在 2‰～ 8‰之间 ;在 1 1月、1 2月的北纬渔场和 1 2月上半月在南纬西部渔场 ,黄鳍金枪鱼的上钩率均大于 4‰ ,而在南纬中部渔场 (0 1°S～ 0 5°S ,2 4°W～ 1 8°W )黄鳍金枪鱼的上钩率最低 ,小于 1‰ ;箭鱼的上钩率在钓捕海域大体在 2‰以下 ,其它低经济价值的鱼上钩率几乎都小于 1‰。本文探讨了影响上钩率的因素。     

金枪鱼延绳钓钓具的最适浸泡时间

根据2010年10月—2011年1月金枪鱼延绳钓海上调查数据,分两种起绳方式,建立每次作业每一根支绳的浸泡时间计算模型。将钓具的浸泡时间以1 h为间隔分别统计每个区间的支绳数量及大眼金枪鱼(Thunnus obesus)、黄鳍金枪鱼(Thunnus albacores)的渔获尾数,并计算其钓获率(CPUE)。结果表明:1)大眼金枪鱼和黄鳍金枪鱼的CPUE都随浸泡时间的增加呈现先增后减的趋势,这是由于饵料的诱引效果变化及渔获的丢失引起的;2)二次曲线可拟合浸泡时间与大眼金枪鱼和黄鳍金枪鱼CPUE的关系;3)大眼金枪鱼和黄鳍金枪鱼CPUE最高的浸泡时间分别为9.9 h和10.1 h。建议:1)今后在金枪鱼延绳钓作业中,保证每一根支绳在水中的浸泡时间为9.5~10.5 h,以提高捕捞效率并减少副渔获物;2)可把延绳钓钓具的浸泡时间作为有效捕捞努力量,并用于CPUE的标准化。研究结果可用于提高捕捞效率并减少副渔获物的技术方案制订,并为渔业生产和CPUE的标准化提供科学参考。     

Alternative error distribution models for standardization of catch rates of non-target species from a pelagic longline fishery: billfish species in the Venezuelan tuna longline fishery

Alternative error distributions were evaluated for calculating indices of relative abundance for non-target species using catch and effort data from commercial fisheries. A general procedure is presented for testing the underlying assumptions of different error distributions. Catch rates, from an observer program, of billfish caught mainly as bycatch in a pelagic tuna longline fishery in the Western Central Atlantic were standardized. Although catches of billfishes are not common in pelagic tuna longline fisheries, these fisheries are one of the main sources of fishing mortality for these stocks in the central Atlantic due to the magnitude and spatial extent of longline fishing effort. Billfish CPUE data are highly skewed with a large proportion of zero observations. Delta distribution models can accommodate this type of data, and involve modeling the probability of a non-zero observation and the catch rate given that the catch is non-zero separately. Three different Delta models were compared against other error distributions, including the lognormal, log-gamma, and Poisson. Diagnostic checks and deviance table analyses were performed to identify the best error distribution and the set of factors and interactions that most adequately explained the observed variability. The results indicated that the Delta-lognormal model (a binomial error distribution for the probability of a non-zero catch and lognormal error for the positive catch rates) complied best with the underlying characteristics of the data set. Analyses of catch rates for blue marlin, white marlin and sailfish confirmed the spatio-temporal nature of their distribution in the central Atlantic and Caribbean Sea. Also, the analyses indicated that catch rates of billfish differed among fishing vessel types; larger vessels had a higher probability of catching blue marlin, the more oceanic-oriented species, and lower probabilities of catching the more coastal-oriented species white marlin and sailfish. Standardized catch rates indicated in general a lower relative abundance for blue and white marlin in the most recent years, although estimated confidence intervals overlap through the years especially for white marlin.     

基于GAM模型分析水温垂直结构对热带大西洋大眼金枪鱼渔获率的影响

通过模型分析环境变量对延绳钓大眼金枪鱼渔获率的影响,评估适宜垂直活动空间对大西洋大眼金枪鱼延绳钓渔获率的作用。首先采用回归分析检验环境变量对延绳钓渔获率(由单位捕捞努力渔获量(catch per unit fishing effort,CPUE)表示)的影响显著性,结合时空变量,采用GAM(generalized additive model)模型分析各变量对大眼金枪鱼CPUE非线性作用。模型结果表明,环境因子和时空变量对热带大西洋延绳钓大眼金枪鱼渔获率空间分布影响明显。大西洋大眼金枪鱼延绳钓的高渔获率月份出现在夏季和冬季,空间上在赤道以北和30?~50?W。12℃等温线深度对大眼金枪鱼延绳钓渔获率的影响表现为抛物线形状,高渔获率出现在深度较浅的250 m水层,随着12℃等温线深度的增加,大眼金枪鱼延绳钓渔获率降低。温跃层下界深度和深度差对大眼金枪鱼延绳钓渔获率的影响都是穹顶状。随着温跃层下界深度值和深度差由小变大至200 m,延绳钓渔获率递增;温跃层下界深度和深度差超过200 m后,延绳钓渔获率变小。温跃层下界深度和深度差对大眼金枪鱼延绳钓渔获率影响显著的水层分别是200 m和50 m。研究结果显示,12℃等温线深度和温跃层对热带大西洋延绳钓大眼金枪鱼渔获率影响是交叉的,在大眼金枪鱼适宜垂直活动水层受限到和延绳钓作业深度相同时,延绳钓渔获率最高;在适宜垂直活动空间过深或者过浅时,延绳钓渔获率都变小,但可以通过改变作业方式提高渔获率。采用延绳钓CPUE进行渔场和资源评估要考虑金枪鱼适宜垂直活动空间。     

金枪鱼延绳钓渔捞日志管理现状与趋势

金枪鱼渔捞日志作为金枪鱼数据收集系统的一部分,在区域性国际渔业组织履约中扮演了重要的角色.本文梳理了国际渔业组织涉及金枪鱼延绳钓渔捞日志的履约要求,分析了部分国家或地区金枪鱼渔捞日志管理要求,论述了我国金枪鱼延绳钓渔捞日志管理中存在的问题,并提出了改进建议和发展方向:(1)渔捞日志嵌入船位监控系统,缩短渔捞日志上交的时效性,提高日志填写的准确性;(2)统一金枪鱼渔业数据收集系统,建立大型金枪鱼数据库,使渔业数据规模化、标准化.     

The effects of mesoscale oceanographic structures and ambient conditions on the catch of albacore tuna in the South Pacific longline fishery

Albacore tuna (Thunnus alalunga) exhibit patchy concentrations associated with biological process at a wide range of spatial scales, resulting in variations in their catchability by fishing gears. Here, we investigated the association of catch variation for pelagic longlines in the South Pacific Ocean with oceanographic mesoscale structures (in horizontal dimension) and ambient conditions (in vertical dimension). The distribution of albacore tuna as indicated by catch per unit effort (CPUE) of longlines was significantly related to the presence of mesoscale structures, with higher CPUE found at locations closer to thermal fronts and with greater gradient magnitudes, as well as areas marked by peripheral contour line of the anticyclone indicated by Sea Surface Height Anomalies ~0.05 m. Surface mesoscale current velocity had the negative effect on the catch, probably as a result of decreased catchability by shoaling the hook depth. Vertical distribution of albacore in the survey region of South Pacific Ocean was hardly restricted by ambient temperature and oxygen concentration, though effect of ambient temperature was relevant and showed a negatively linear correlation with CPUE at the range of 20–24°C. On the contrary, albacore distribution was evidently dominated by the water depth and showed strong preference on water depth of 200 m, which was likely a representative feeding layer. The presence of prey resources and their accessibility by albacore revealed by mesoscale structures in the biological and physical processes, and catchability determined by the location of the baited hooks comprehensively contribute to the variability of catch.     

Hawaii longline tuna fishery temporal trends in standardized catch rates and length distributions and effects on pelagic and seamount ecosystems

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Dynamic simulation of tuna longline gear using numerical methods

ABSTRACT:   The underwater shape and hook depth of tuna longline gear are important factors determining fishing performance. In this study, how the shape of tuna longline gear changes in response to sea conditions and gear rigging is explained. Physical models of underwater gear shape were made to simulate fishing gear and analyzed according to the direction and velocity of currents. Then experiments with small-scale models were conducted in a flume tank to confirm the accuracy of the simulation analysis. Finally, the simulation was examined relative to actual longline fishing gear. This approach provided an improvement over previous analytical methods that did not consider fishing gear shape in response to different sea conditions. A useful result is an improved understanding of the relationship between ocean currents and the configuration of longline gear (the shortening ratio, and number of hooks per basket). These factors affect hook depth which, in turn, affects selectivity. Application of these results could lead to more effective and efficient fishing under different sea conditions.