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

Michiru Shiga  Daisuke Shiode  Satoshi Hayashi  Tadashi Tokai  Fuxiang Hu 《Fisheries Science》2008,74(3):479-487

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.  相似文献   

Movements,behavior, and habitat utilization of yellowfin tuna (Thunnus albacares) in waters surrounding the Revillagigedo Islands Archipelago Biosphere Reserve,Mexico     

Kurt M. Schaefer  Daniel W. Fuller  Gabriel Aldana 《Fisheries Oceanography》2014,23(1):65-82

The movements, behavior, and habitat utilization of yellowfin tuna, Thunnus albacares, following capture and release with archival tags in the Revillagigedo Islands Archipelago Biosphere Reserve (RIABR), Mexico, are described from analyses of 16 578 days of time‐series data, downloaded from 52 archival tags recovered from yellowfin (78–173 cm in length and 1.7–8.0 yr of age) at liberty from 93 to 1773 days ( = 411 days), collected during 2006–2012. An unscented Kalman filter model with sea‐surface temperature measurements integrated (UKFsst) was used to process the archival tag data sets to obtain improved estimates of geographic positions, most probable tracks (MPTs), and movement parameters. The MPTs indicate restricted movements, low levels of dispersion, and fidelity of yellowfin tuna to the RIABR. The median parameter estimates from the UKFsst model for errors in longitude (σ_x) and latitude (σ_y) were 0.46° and 1.84°, respectively, for directed movements (u and v) –0.05 NM day^?1 and –0.05 NM day^?1, respectively, and for dispersive movement (D) 117.99 NM² day^?1. Analyses of daily timed depth and temperature records resulted in the classification of the data into four distinct behaviors. There are significant differences among ages in the durations of Type I and Type II diving behaviors and in the daytime and nighttime vertical habitat utilization distributions. The oceanography surrounding the RIABR appears to have a profound influence on the movements, behavior, and habitat utilization of yellowfin in this area.  相似文献   

浙江自然海区逃逸美国红鱼食性研究   总被引：1，自引：0，他引：1  

金海卫  徐汉祥  许文军  薛利建 《海洋水产研究》2008,29(1):103-108

通过对浙江自然海区逃逸美国红鱼胃含物的分析,从食料生物组成、食性类型、摄食强度及营养级4个方面对浙江自然海区逃逸美国红鱼的食性进行了探讨。结果表明,美国红鱼属游泳动物食性。主要摄食鱼类、长尾类、短尾类和头足类,兼食口足类和多毛类。其食料生物组成和食性类型与原栖息地有较大差异。逃逸美国红鱼的摄食率为80.28%,最高饱满度系数达60.93‰,平均10.26‰。根据计算,其饵料的生境宽度为4.09,营养级为3.43级。浙江自然海区美国红鱼是一种凶猛的中级肉食性鱼类。  相似文献   

微山湖河蟹养殖区与非河蟹养殖区细菌胞外酶的比较研究     

房姝  石静  姚凯  孟德波  徐铖  郑祖亮  周晶 《畜牧与饲料科学》2011,(12)

为了研究微山湖河蟹养殖区与非河蟹养殖区水体和底泥中异养细菌胞外产酶（蛋白酶、淀粉酶、脂肪酶、脲酶）的差别．对这2处环境中的微生物进行了初步筛选和分离,得到25株菌,分别在含有蛋白质、脂肪、淀粉、脲的固体培养基上培养观察。并测量记录菌落和菌圈大小。结果表明,河蟹养殖区产蛋白水解酶和脂肪水解酶的细菌明显多于非河蟹养殖区,而产淀粉水解酶和脲酶的细菌数量两者相差不大。  相似文献   

羔羊育肥技术   总被引：1，自引：0，他引：1  

沙文锋  陈启康  顾拥建  朱娟  戴晖 《金陵科技学院学报》2006,22(3):87-90

羔羊肉具有瘦肉多、脂肪少、味美鲜嫩、容易消化等特点;育肥羔羊具有增重快、饲料报酬高、产品成本低、生产周期短、经济效益高等特点.因此,世界上养羊业发达国家都把肥羔生产作为羊肉生产的重点.介绍了国内外肉羊业的发展现状、趋势,国外先进的肥羔生产技术,羔羊育肥的技术要点;期望对我国的羊肉生产和羊肉品质的提高有所帮助.  相似文献   

重瓣红纸扇组培苗工厂化繁育技术体系构建          下载免费PDF全文

谭嘉娜  官锦燕  许玉婵  陈双艳  罗剑飘  罗青文 《广东农业科学》2023,50(10):130-140

【目的】建立重瓣红纸扇组培苗高效的工厂化繁育技术体系，为实现该品种规模化生产提供技术支撑。【方法】以重瓣红纸扇母株的茎尖、茎段为外植体，研究消毒剂种类与方式、基本培养基、激素种类及配比、光质等因素对其组培苗繁育效率的影响，并研究不同季节对组培苗移栽成活率及生长的影响。【结果】重瓣红纸扇外植体遇酒精容易死亡，无菌水清洗可以减轻酒精对外植体的毒害，10%H2O2 处理 10 min 与0.1% HgCl2 处理 8 min 可获得大量的无菌材料；3/2MS 基本培养基诱导芽体长势好；外植体在 3/2MS+BA 3.0mg/L+NAA 0.2 mg/L 培养基上芽的诱导率高且芽体粗壮；探讨不同配方下的增殖方式对组培苗工厂化生产效率的影响，结果发现 3/2MS+BA 0.5 mg/L+NAA 0.1 mg/L+ 蛋白胨 0.1 g/L 培养基上以切段繁殖方式效率更高，组培苗在3/2MS+NAA 0.04~0.05 mg/L+IBA 0.01 mg/L 培养基上生根率达 100%，根系粗壮，植株生长旺盛；不同季节对重瓣红纸扇组培苗的驯化移栽影响差异显著；不同光质对其组培苗的生长发育阶段和叶绿素含量均存在显著性差异，荧光灯处理适用于增殖扩繁，LED 灯 80% 红光 +20% 蓝光处理适用于生根阶段壮苗培养。【结论】试验结果获得重瓣红纸扇外植体有效的消毒方法、组培芽体诱导增殖和生根壮苗适宜的培养基配方与光质条件，为重瓣红纸扇工厂化育苗提供了理论依据。  相似文献   

人工养成斑鱼祭的繁殖试验          下载免费PDF全文

单乐州  邵鑫斌  张立宁  马建忠  陈琛  赵伟华 《水产科技情报》2022,49(5):262-265

为实现斑[HT5”,7]鱼[KG-*3]祭全人工繁育,在室内水泥池采用人工养成的1龄和2龄斑[HT5”,7]鱼[KG-*3]祭进行了繁殖试验。试验中观察发现,斑[HT5”,7]鱼[KG-*3]祭亲鱼均在傍晚天色刚暗时开始自然产卵,持续约0.5 h后产卵结束；斑[HT5”,7]鱼[KG-*3]祭亲鱼有摄食鱼卵的习性,产卵后需立即进行流水集卵。2龄斑[HT5”,7]鱼[KG-*3]祭(共147尾,总体质量15.6 kg)自开始产卵至结束共持续40 d,其间仅有2 d未产卵,共产卵3 594 g,分离得到上浮卵1 372 g,上浮卵率为38.2%；产卵开始时水温14.7 ℃,结束时21.3 ℃；产卵后的亲鱼陆续批量死亡。1龄斑[HT5”,7]鱼[KG-*3]祭(共611尾,总质量22.6 kg)自开始产卵至结束共持续20 d,其间有5 d未产卵,共产卵488 g,分离得到上浮卵213 g,平均上浮卵率为43.6%,产卵后的亲鱼未发现有批量死亡现象。  相似文献   

水培蕹菜使用吡唑醚菌酯的水生生态系统风险评估          下载免费PDF全文

宋雯  王强  张怡  徐明飞  陈丽萍  苍涛  吴长兴 《农业环境科学学报》2022,41(6):1202-1210

为研究水培蕹菜使用吡唑醚菌酯对水生生物的潜在影响，在水培蕹菜白锈病发病初期，喷施25%吡唑醚菌酯悬浮剂和9%吡唑醚菌酯微囊悬浮剂，测定水培蕹菜和水体中的吡唑醚菌酯残留量，并结合毒理学数据评估其对水生生态系统的暴露风险。结果表明：吡唑醚菌酯在水培蕹菜和水中降解较快。悬浮剂和微囊悬浮剂在植株中的消解半衰期分别为2.9 d和3.9 d，微囊悬浮剂较悬浮剂在植株上的持效期更长。两种剂型在水中的消散半衰期都小于2 d，微囊悬浮剂在水中的有效浓度小于悬浮剂。基于暴露浓度峰值和时间加权平均浓度进行风险评估，悬浮剂对水生脊椎动物和无脊椎动物的急性和慢性风险商值，及其对初级生产者的慢性风险商值均大于1；微囊悬浮剂对每一类水生生物的风险商值都小于悬浮剂，但其对水生生物的急性暴露风险同样不可接受（风险商值仍大于1），慢性风险商值仅在基于时间加权平均浓度计算时小于1。研究表明，吡唑醚菌酯在水培蕹菜上使用对水生生态系统的风险不容忽视，应重点关注鱼和无脊椎动物的暴露风险。建议在水生蔬菜生产中谨慎使用吡唑醚菌酯，同时修订吡唑醚菌酯在水生蔬菜上的限量标准。  相似文献   

Horizontal movements,utilization distributions,and mixing rates of yellowfin tuna (Thunnus albacares) tagged and released with archival tags in six discrete areas of the eastern and central Pacific Ocean     

Kurt M. Schaefer  Daniel W. Fuller 《Fisheries Oceanography》2022,31(1):84-107

A total of 1522 yellowfin tuna, Thunnus albacares, were captured, tagged, and released with surgically implanted archival tags (ATs), in six discrete areas of the eastern and central Pacific Ocean, during 2002 through 2019. Of 483 ATs returned (31.7%), 227 ATs from yellowfin (48–147 cm in fork length) at liberty from 32 to 1846 d ( = 300.1 d) provided suitable data sets which were processed using an unscented Kalman filter model with sea-surface temperature measurements integrated (UKFsst) in order to obtain most probable tracks and movement parameters. Although some differences were observed in the movement patterns for fish from within and among the six release areas, 99% of the 227 fish remained within 1000 M of their release locations, indicating limited dispersion and fidelity to release locations. The median movement parameter D, which defines dispersion from the UKFsst model, for the fish released in the offshore equatorial areas showed much greater dispersion rates compared to those for the fish released along the coast or around islands. The rates of mixing of yellowfin among the release areas were found to be dependent on the distances between release areas, with, in general, the greatest mixing occurring among areas in closest proximity, whereas for the two areas offshore Mexico and the two offshore equatorial areas, the rates of mixing were nonexistent or negligible.  相似文献   

An integrated scheme for the management of drifting fish aggregating devices in tuna purse seine fisheries     

Liming Song  Huihui Shen 《Fisheries Management and Ecology》2023,30(1):56-69

Drifting fish aggregating devices (dFADs) are extensively used in modern tuna purse seine fisheries. The use of dFADs has greatly improved fishing efficiency and generated substantial economic returns in purse seine fisheries, but adverse impacts on tuna juveniles, associated species and marine ecosystems are still of concern. Based on an analysis of current challenges in dFAD management measures in tuna regional fishery management organisations (t-RFMOs), we explored opportunities to strengthen dFAD management in tuna fisheries. An integrated dFAD management scheme with multiple tools that account for different usage stages of a dFAD needs to be organised to regulate, track, monitor and recover in tuna purse seine fisheries. We recommend that (1) dFAD-associated definitions should be standardised to provide operational guidance for dFAD activities; (2) all deployed dFADs should be counted towards dFAD limits on active dFADs, except those reported as lost and abandoned; (3) a regional dFAD tracking and monitoring program should track dFAD paths based on daily position reported to RFMOs directly, in addition to mandatory dFAD marking requirements; and (4) a framework of compensation mechanisms should provide financial support for joint dFAD recovery and eco-compensation.  相似文献