The effects of density and artificial substrate on intensive shrimp Litopenaeus vannamei nursery production     

《Aquacultural Engineering》2020

Recirculating aquaculture systems (RAS) can be installed indoors, allowing year-round production of tropical animals in nearly any climate. A nursery phase is commonly used in Litopenaeus vannamei production since it allows for enhanced biosecurity and better quantification of animals while reducing space requirements. However, it is unclear whether animal density and inclusion of artificial substrate may improve shrimp performance during the nursery phase. In this experiment, we compared shrimp production parameters in two stocking densities with or without the use of an artificial substrate by creating four treatments: low-density LD; 1500 PL/m⁻³, low-density with substrate LDS, high-density HD; 3000 PL/m⁻³), and high-density with substrate (HDS). The LDS and HDS treatments included 0.46-m² of high-density polyethylene 2.5-cm mesh as a substrate, which increased the tank surface area by 21 %. Each treatment was randomly assigned to four 160-l culture tanks, each with a biofilter. The shrimp had an initial weight of 4 mg and were grown for 50 days. The low-density treatments had significantly higher dissolved oxygen (DO) and pH than the high-density treatments (P ≤ 0.001). Specifically, LDS had the highest DO and pH followed by the LD, HD, and HDS treatments, respectively. High-density treatments had significantly higher NO₂-N levels than low-density treatments during week 2 of the experiment when an unusually high concentration of nitrite was observed. FCR was significantly lower in both low-density treatments than in high-density treatments. At harvest, the total biomass (kg m⁻³) was significantly higher in high-density treatments than in low-density treatments (P ≤ 0.001), and the HDS treatment had a significantly greater biomass output than HD. Producers should consider artificial substrate and higher densities during nursery production to maximize shrimp production; however, the effects on water quality should also be taken into account.  相似文献   

South-Western blot mapping方法的建立及其应用于锥虫细胞核中DNA结合蛋白的观察     

欧永春  T.Baltz 《中国兽医学报》1992,(2)

South-Westerm blot mapping是一种结合Western blotting和Southern blotting某些特点的方法.本文介绍用其成功地观察到锥虫核蛋白中DNA结合蛋白的情况,并对一个分子量在40000左右、于较严谨条件下与DNA结合的核蛋白进行了特性鉴定.该蛋白等量地存在于锥虫的前循环期和血液期,对双链DNA有较大的亲和力,并能与酵母菌复制起始片段结合.本文还介绍了锥虫细胞核的提取技术和核蛋白的制备技术.  相似文献   

Use of Porcine Meal in Plant‐based Practical Diets for Pacific White Shrimp,Litopenaeus vannamei          下载免费PDF全文

Xuan Qiu  D. Allen Davis 《Journal of the World Aquaculture Society》2018,49(3):582-589

Two growth trials were conducted to evaluate and confirm the efficacy of a porcine meal (PM) with high protein content (>90%) as an alternative feed ingredient in commercial‐type feed formulation for Pacific white shrimp, Litopenaeus vannamei. Six experimental diets were formulated for the two growth trials. The first five diets contained increasing levels (0, 1, 2, 4, and 6%) of PM as a replacement for soybean meal in a plant‐based diet with low inclusion level (6%) of fish meal (FM). The last experimental diet was produced utilizing 4.2% PM to completely replace FM. In Trial 1, shrimp (1.5 g initial mean weight, 20 shrimp/tank, n = 4) were offered test diets for 6 wk in a semirecirculation system. At the end of Trial 1, shrimp fed with the diet containing 6% PM exhibited significantly enhanced weight gain (WG), feed conversion ratio (FCR), and survival compared to those fed with the diet devoid of FM. As survival was poor across all treatments and different densities could mask growth results the trial was repeated. In Trial 2, shrimp (0.85 g, 15 shrimp/tank, n = 4) were offered diets for 6 wk. Dietary supplementation of PM at 6% significantly improved WG, FCR, and apparent net protein retention in contrast with the treatment devoid of FM, confirming the same trends in Trial 1. No significant difference was detected in protein, lipid, moisture, and mineral profiles of whole‐body shrimp as well as survival across all the treatments. Results of this study indicate that PM is a good high protein source in shrimp feeds, which can be included up to 6% in the low FM‐based diet without compromising the growth of shrimp.  相似文献   

盛夏西太平洋副热带高压对陕西降水的影响     

赵强  郭莉  张鸿雁  严华生 《中国农业气象》2013,34(3)

利用1961-2008年陕西78个气象站7-8月降水资料、西太平洋副高逐月指数资料及500hPa位势高度场和700hPa风场月平均再分析资料,通过相关、回归分析、小波凝聚谱分析等方法探讨盛夏西太平洋副热带高压对陕西降水的影响及机制,为盛夏陕西降水的气候预测提供依据.结果表明,盛夏副高强度、脊线、西伸脊点指数与陕西降水关系密切,副高偏强偏西时陕西降水偏多,副高偏北时陕西北部降水偏多、南部偏少.8月副高3个指数与陕西降水的相关关系更为密切,通过显著性检验的站点明显增多.副高的强度和位置变化引起副热带和中高纬度大气环流的异常,进而影响陕西降水.8月副高偏强偏西时,巴尔喀什湖阻高增强,700hPa西南季风的水汽输送增强,陕西位于冷暖空气交汇区,降水偏多;副高偏南时,水汽辐合区位于陕南,陕西南部多雨、北部少雨;副高偏北时,水汽辐合区位于陕北,陕西北部多雨、南部少雨.8月副高强度指数与同月陕西降水的显著共振周期为7 ～8a,且副高强度变化超前于陕西降水变化1.26a,说明8月副高强度的年际变化是引起同月陕西降水年际变化的重要原因.  相似文献   

Establishing climate–growth relationships for yelloweye rockfish (Sebastes ruberrimus) in the northeast Pacific using a dendrochronological approach     

BRYAN A. BLACK  GEORGE W. BOEHLERT  MARY M. YOKLAVICH 《Fisheries Oceanography》2008,17(5):368-379

We applied dendrochronology (tree‐ring) methods to develop multidecadal growth chronologies from the increment widths of yelloweye rockfish (Sebastes ruberrimus) otoliths. Chronologies were developed for the central California coast, a site just north of Vancouver Island, British Columbia, and at Bowie Seamount west of the Queen Charlotte Islands, British Columbia. At each site, synchronous growth patterns were matched among otoliths via the process of cross‐dating, ensuring that the correct calendar year was assigned to all increments. Each time series of growth‐increment measurements was divided by the values predicted by a best‐fit negative exponential function, thereby removing age‐related trends. These detrended time series were averaged into a master chronology for each site, and chronologies were correlated with monthly averages of sea surface temperatures, upwelling, the Northern Oscillation Index, and the Pacific Decadal Oscillation. The two northern growth chronologies positively correlated with indices of warm ocean conditions, especially from the prior summer through the spring of the current year. During the same period, the California chronology positively correlated with indices of cool ocean conditions, indicating an opposing productivity regime for yelloweye rockfish between the California Current and the Gulf of Alaska. Overall, this study demonstrates how tree‐ring techniques can be applied to quickly develop annually resolved chronologies and establish climate–growth relationships across various temporal and spatial scales.  相似文献   

Application of sperm cryopreservation in selective breeding of the Pacific oyster,Crassostrea gigas (Thunberg)     

Serean L Adams  John F Smith  Rodney D Roberts  Achim R Janke  Nick G King  Harry Robin Tervit  Stephen C Webb 《Aquaculture Research》2008,39(13):1434-1442

The robustness of Pacific oyster, Crassostrea gigas (Thunberg), sperm cryopreservation in the context of selective breeding based on family lines was investigated. Irrespective of egg density, high fertilization success was achieved with cryopreserved sperm when sperm:egg ratios of 1000:1 to 10 000:1 were used. Variation among replicate runs on the same oyster batches was minimal, indicating that cryopreservation and larval rearing procedures were repeatable. Twenty independent single male–female crosses were made to assess the utility of cryopreserved sperm in selective breeding. The fertility of unfrozen sperm was generally a poor predictor of cryopreserved sperm fertility. Based on D‐larval yields, 17 of the 20 crosses were likely to yield adequate spat for selective breeding (>10⁵ D‐larvae from 1 million eggs), two were marginal (5 × 10⁴ D‐larvae) and one was inadequate (4 × 10³ D‐larvae). An alternative fertilization strategy to improve D‐yield from a given number of sperm was then tested. Fertilizing 10 million eggs at a sperm:egg ratio of 200:1 increased the total D‐yield when compared with fertilizing 1 million eggs at a sperm:egg ratio of 2000:1 for the same male–female pair. We conclude that, despite wide variation in fertility, cryopreserved sperm is useful for family production.  相似文献   

Reducing elasmobranch bycatch: Laboratory investigation of rare earth metal and magnetic deterrents with spiny dogfish and Pacific halibut     

Allan W. Stoner  Stephen M. Kaimmer 《Fisheries Research》2008,92(2-3):162-168

Spiny dogfish (Squalus acanthius) comprises a significant unwanted bycatch on demersal longlines set for halibut and cod in shelf waters of the east and west coasts of North America. In this laboratory study, attacks on baits were tested in the presence of two different rare earth materials (neodymium–iron–boride magnets and cerium mischmetal) believed to deter elasmobranch catch. Experiments were made with spiny dogfish and with Pacific halibut (Hippoglossus stenolepis) in pairwise tests of the rare earth materials and inert metal controls. Dogfish attacked and consumed baits tested with cerium mischmetal at a lower frequency than controls. Times to attack the baits were significantly higher in the presence of mischmetal, as were numbers of approaches before first attack. The time differential between mischmetal and control treatments and the number of baits consumed converged with increasing food deprivation (1 h, 2 d, and 4 d), but treatment differences were always significant. Cerium mischmetal appeared to be irritating to dogfish and may disrupt their bait detection and orientation abilities. Magnets also appeared to irritate dogfish but provided no protection for baits in feeding trials. Pacific halibut showed no reaction whatsoever to the rare earth magnets or cerium mischmetal. Mischmetal, therefore, may be useful in reducing spiny dogfish bycatch in the halibut fishery. Disadvantages in using mischmetal in commercial operations are expense, hazardous nature, and relatively rapid hydrolysis in seawater.  相似文献   

西北太平洋公海秋刀鱼渔场浮游动物数量分布的初步研究     

朱清澄  刘昊  马伟刚  刘瑜  夏辉  花传祥 《水产科学》2008,27(1):13-16

根据2005年7—10月在北太平洋E 150°~158°56′、N 42°34′~46°25′进行秋刀鱼资源探捕所获得的15个站点浮游动物样本资料,测得甲壳纲的桡足类、端足类、糠虾类、磷虾类,毛颚类、腔肠动物以及被囊动物等的代表种。其中桡足类占绝对优势,隶属于1目4科5属8种。浮游动物生物量4~699 mg/m3,均值168.6 mg/m3。根据浮游动物的种类、分布状况及优势种类的强弱,判断和分析黑潮暖流的强弱趋势,对确定秋刀鱼渔场的南北位置具有重要参考价值。  相似文献   

Benefits and risks for Melanesian households from commercialising Canarium indicum          下载免费PDF全文

《Asia Pacific viewpoint》2017,58(3):388-395

This research note discusses the benefits and risks for Melanesian households arising from attempts to increasingly commercialise Canarium indicum, an edible tree nut indigenous to Papua New Guinea, the Solomon Islands and Vanuatu. Qualitative data were generated during workshops and interviews with Canarium industry stakeholders about the impacts associated with a series of interventions designed to encourage further commercialisation of Canarium. The findings are organised according to three dimensions that elucidate the social implications of industry development for local communities: (i) income and growth; (ii) equity; and (iii) voice and choice. Broader distribution of benefits within and between countries, as well as among supply chain actors, requires a stronger policy response at regional (Melanesia) and national scales, equitable gender representation to avoid reinforcing existing inequalities, and delegation of decision‐making power to the appropriate level to facilitate effective community participation and their links with other stakeholders. Thus, it remains to be seen whether Canarium‐related benefits arising from its commercialisation can be sufficiently reliable compared with either other sources of income (e.g. existing employment opportunities for those located near urban areas) or utilising the resource for subsistence purposes.  相似文献   

月相对北太平洋海域柔鱼钓获率的影响   总被引：6，自引：0，他引：6  

陈新军  田思泉  钱卫国 《海洋渔业》2006,28(2):136-140

月相是影响光诱鱿钓作业效率的重要因素之一。通过对1995~2000年北太平洋8~10月150°E~165°E柔鱼盛渔期的生产统计分析,各月月相在朔期间的产量分别为望期间产量的1.16、1.53和1.20倍,平均日产量分别增加0.38 t/d、0.9 t/d和0.21 t/d。经过GAM模型分析,月相对日产量的影响是显著的,其PC f值均在0.14以下,模型分析结果满意。  相似文献