Trends in NE Atlantic landings (southern Portugal): identifying the relative importance of fisheries and environmental variables

Time series of commercial landings from the Algarve (southern Portugal) from 1982 to 1999 were analyzed using min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA). These techniques were used to identify trends and explore the relationships between the response variables (annual landings of 12 species) and explanatory variables [sea surface temperature, rainfall, an upwelling index, Guadiana river (south‐east Portugal) flow, the North Atlantic oscillation, the number of licensed fishing vessels and the number of commercial fishermen]. Landings were more highly correlated with non‐lagged environmental variables and in particular with Guadiana river flow. Both techniques gave coherent results, with the most important trend being a steady decline over time. A DFA model with two explanatory variables (Guadiana river flow and number of fishermen) and three common trends (smoothing functions over time) gave good fits to 10 of the 12 species. Results of other models indicated that river flow is the more important explanatory variable in this model. Changes in the mean flow and discharge regime of the Guadiana river resulting from the construction of the Alqueva dam, completed in 2002, are therefore likely to have a significant and deleterious impact on Algarve fisheries landings.     

Relationships between catch and effort in Fijian multispecies reef fisheries subject to different levels of exploitation

Abstract The catch-per-unit-effort (CPUE) and value-of-catch-per-unit-effort (VPUE) of reef-associated fish species from six Fijian native fishing grounds ( qoliqoli ) subject to different fishing intensities were determined using records of fishing activity from a voluntary logbook scheme. Line and spear fishing techniques were used for more than half the total fishing time (h person^-1 d^-1) in all qoliqoli , and yet the favoured technique in a given qoliqoli was frequently less efficient (lower CPUE) than other techniques. The popularity of relatively ineffective fishing methods implies that fishermen did not always attempt to maximize their catch rates. To compare fishing effort in different qoliqoli , all effort was rescaled on the basis of its recorded efficiency (measured as multispecies CPUE) and expressed as hours equivalent to boat-based spear fishing over coral by day to catch fish for sale. Total fishing intensity in the six qoliqoli ranged from 72 to 4310 h km^-2 reef year^-1. The relationship between catch and effort was linear at all fishing intensities, suggesting that the qoliqoli were all fished on a sustainable basis. Furthermore, whilst there was a significant difference in CPUE and VPUE between the one or two qoliqoli with lowest fishing intensity and all the others, there were no significant differences between these other qoliqoli in terms of the VPUE of the saleable multispecies boat catch or the CPUE of species from piscivorous and carnivorous genera ( Epinephelus, Lethrinus and Plectropomus ) which the fishermen prefer to catch.     

生姜根结线虫病原鉴定及发生规律

采用田间调查、接种试验、电镜与显微镜观察以及酯酶同工酶电泳等方法,对引发生姜癞皮病的病原及发生规律进行了研究.结果表明,引起生姜癞皮病的病原为南方根结线虫Meloidogyne incognita.该病在每年6月中旬开始发生,8、9月份危害严重.病原在生姜上一年可发生完整的4代,完成1代平均约需35天.病原主要在0～40cm的土层内分布和危害,但具体分布情况依寄主生长状况而稍有差异.南方根结线虫繁殖速率受初始接种密度的影响也很大,当初始接种密度较低时,线虫繁殖速率较高,初始接种密度增大,繁殖速率降低,其平衡密度为每100g干土746.20个卵.     

基于GAM的长江口鱼类资源时空分布及影响因素

根据2006至2017年长江口及其邻近海域鱼类资源调查,运用广义加性模型研究长江口鱼类资源密度与环境因子之间的关系,并对2017年鱼类资源密度的时空分布进行预测。结果显示,春夏秋冬四个季节最佳GAM偏差解释率分别为69.6%、55.9%、51.4%和47.4%,交叉验证回归线斜率的平均效应为0.62～0.88。盐度、水温和溶解氧是影响长江口鱼类资源密度的主要环境影响因子且在不同季节对鱼类资源密度有不同的影响机制。总体上,在春、夏、秋季,盐度与鱼类资源密度之间存在正向相关性;在夏、秋、冬季,水温对鱼类资源密度有显著影响,在秋季与鱼类资源密度之间存在正向相关性;在春、秋、冬季,溶解氧对鱼类资源密度有显著影响,在冬季与鱼类资源密度之间存在正向线性相关。研究表明,2017年夏季鱼类资源密度较高;在长江口南支的自然延伸水域存在鱼类资源密度的相对低值,在崇明岛向海自然延伸方向水域存在鱼类资源密度的相对高值。后续研究将对长江口鱼类资源进行不同生态类型区分,以期更加准确地掌握影响各生态类型鱼类时空分布的环境因素及其时空分布信息。     

盐阳离子类型对红壤裂缝开闭规律的影响

为了探究灌溉水中盐离子浓度及类型对土壤裂缝变化过程的影响,为南方灌溉用水安全提供数据理论支持,采用蒸馏水配置15.0,10.0,5.0和2.5 g/L等4个质量浓度梯度的NaCl,KCl,CaCl2和MgCl2等4种类型溶液,分别浸泡南方亚热带地区的典型红壤,并且采用恒温蒸发模拟干燥过程和喷湿法模拟增湿过程,结合数字图...     

洪堡洋流系统内重要渔业资源对气候和海洋环境变化的响应研究进展

洪堡洋流系统支撑着世界上最大的中上层渔业,同时也是受到气候胁迫最为显著的海洋东边界流系统。本文概述了洪堡洋流系统的海况和渔业现状,围绕秘鲁鳀(Engraulis ringens)、智利竹■鱼(Trachurus murphyi)、远东拟沙丁鱼(Sardinops melanosticta)和茎柔鱼(Dosidicus gigas)4种代表性的重要经济渔业物种,总结气候和海洋环境对其生长繁殖、种群结构以及资源波动等影响。研究认为,以上4类中上层关键经济种类的物种丰度和分布均受到季节性、年际和年代际气候变化和洪堡洋流海洋条件的强烈影响,在未来气候变化的影响下,研究洪堡洋流生态系统需要依赖于高能力的综合生态系统模型,需考虑物理、生物和化学环境、营养结构等因素,全面地评估生态系统内各种群的变动规律,进而更加科学地开发和管理该系统的渔业资源。     

基于优势分析法的西印度洋捕捞国和地区渔获量差异初步分析

西印度洋是海洋捕捞作业的重要海域,分析捕捞方渔获种类组成和渔获量是评价渔业资源利用状态的基础,也是确保其资源可持续开发和科学管理的重要支撑。根据FAO提供的1950—2019年西印度洋海域渔获量统计数据,采用优势分析法(dominance analysis)分析了70年间主要捕捞方的渔获种类组成和渔获量,比较不同时间序列下主要捕捞方和捕捞种类对渔获量的贡献率。研究表明,西印度洋海域渔获量整体呈上升趋势,根据突变点检测及渔获量增长趋势可划分为1950—1982年、1983—2005年和2006—2019年3个阶段。各阶段累计渔获量前十的渔获种类、捕捞方不存在显著性差异,长头小沙丁鱼(Sardinella longiceps)累计渔获量最高,鲣(Katsuwonus pelamis)、黄鳍金枪鱼(Thunnus albacores)等种类渔获量对总渔获量的贡献度较高;印度、巴基斯坦和伊朗等是沿海国和地区各阶段渔获量最高的捕捞方,西班牙、法国、日本和中国台湾省等是非沿海国和地区渔获量最高的捕捞方,对各阶段印度洋西部海域总渔获量的贡献度基本都超过10%。研究认为,基于印度洋西部海域渔业资源开发...     

渔业专业网站网络新闻信息源的开发和利用

结合作者的工作实际,分析了渔业网络新闻信息源开发和利用的重要意义,探讨了渔业网络新闻信息源的类型和特点、开发利用流程。     

四川省草地贪夜蛾世代区划

为明确草地贪夜蛾Spodoptera frugiperda在四川省不同地区的发生世代,本文根据四川省2019年、2020年草地贪夜蛾虫情及2010年-2019年近10年气温数据,利用有效积温法则对四川省草地贪夜蛾发生世代数进行预测,并运用ArcGIS进行Kriging插值分析,获得四川省草地贪夜蛾世代区划.结果表明,基...     

延安市土地利用程度评价及政策建议

基于土地利用变更数据,采用改进后刘纪远土地利用程度综合指数模型,分别从总体评价、地域分异规律研究、时间序列研究等3个方面对延安市土地利用程度进行全面评价。结果显示：总体而言,2007年全市及其各区县土地利用程度都低于全省平均水平;地域分异规律方面,土地利用程度呈现出纬度和垂直分异规律,没有呈现出明显的经度分异规律,且随...