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Different culture methods may affect the intensive culture system of Pacific white shrimp （Litopenaeus vannamei） re- garding water quality and growth and economic performance. This study evaluated the potential effects of three culture methods through cultivation of juvenile shrimps under consistent tank management conditions for 84 d. The three methods involved shrimp cultivation in different tanks, i.e., outdoor tanks with cement bottom （mode-C）, greenhouse tanks with cement bottom （mode-G） and outdoor tanks with mud-substrate （mode-M）. Results showed that water temperature was significantly higher in mode-G than that in mode-C （P 〈 0.05）. In contrast to the other two treatments, mode-M had stable pH after 50 d cultivation of shrimps. In the mid-late period, the average concentrations of TAN, NO2-N, DIP and COD were significantly lower in mode-M and mode-G compared with those in mode-C （P 〈0.05）. Despite lack of differences in the final shrimp weight among different treatments （P 〉0.05）, mode-M had significantly higher shrimp yield, survival rate and feed conversion rate （P 〈 0.05） than other modes. There were significant dif- ferences in revenue and net return among different treatments （P 〈 0.05）. These demonstrated that the treatments of mode-G and mode-M were conductive to the intensive culture system ofL. vannamei. 相似文献
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基于巴西陆上沉积盆地基础地质条件,以石油地质理论为指导,运用分析、类比的方法划分盆地类型,并对各类盆地生储盖组合及油气成藏特征进行了研究。分析认为,南美地台经历复杂的构造演化,在巴西境内形成元古宙叠合、显生宙克拉通和中生代萎缩裂谷3大类盆地。元古宙盆地以地层年代久远、构造演化复杂、烃源岩热演化漫长为特征。显生宙克拉通盆地呈现“先断后坳”的演化特征,主体地层序列形成于古生代,有一套普遍发育且受侵入岩影响的烃源岩。中生代萎缩裂谷盆地基础及油气地质两方面均呈现断陷湖盆的特征。通过对巴西陆上盆地区域演化、类型划分、地层及构造特征、生储盖层和成藏特征等方面的探讨,可为中国海外油气区域优选提供一定参考。 相似文献
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1990年,南美委内瑞拉和智科北部之间的安第斯山、东非的Kenya、Rwenzori和Kilimanjaro以及Irian的Jaya(新几内亚)的低纬度高山冰川的覆盖面积近2500km。,安第斯山在这些高山冰川中几乎占据了99％的面积。自小冰期1850年以来,所有这些冰川均具有范围缩小的全球性趋势(表1)。在冰川总体后退的期间,存在着冰川前进的多个亚期：如20世纪20年代和70年代冰川有再次向前推进的全球性趋势。在Cordillera Blanea或整个秘鲁Cordilleras大多数冰川表面从1998年10月至2002年5月或多或少的有持续降雪的覆盖, 相似文献
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文章借鉴国内外传统模式以及工厂化模式下水产养殖、对虾养殖成本收益分析指标体系的设立方法和相关研究理论,以山东省为例,于2016—2019年实地采集得到样本数据,对南美白对虾工厂化养殖模式下的成本收益进行分析。结果表明：①2016—2019年山东省工厂化养殖南美白对虾的总成本呈波动上升趋势,其中可变成本远高于固定成本;②在成本结构方面,工厂化养殖模式下固定成本中最大支出项为固定资产折旧,设备维修费近年来增长明显,可变成本中饲料费用、水电煤费、虾苗费用为主要成本项,其中饲料费用占比最大且呈持续上升趋势;③2016—2019年山东省南美白对虾工厂化养殖的净利润稍有减少,尤其在2018年经历了断崖式下滑,4年来成本利润率和销售利润率降低,养殖利润水平、盈利水平均有所下降;④2016—2019年净利润对于价格、饲料费用、水电煤费、苗种费用的敏感性依次由高到低,2018年养殖效益较差的情况下各项敏感系数绝对值均有所增加。 相似文献
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To investigate the influence of sodium to potassium(Na/K) ratios on the growth performance and physiological response of the Pacific white shrimp( Litopenaeus vananmei), various concentrations of KCl were added to low-salinity well water(salinity 4) in an 8-week culture trial. Six treatments with Na/K ratios of 60:1, 42:1, 33:1, 23:1, 17:1, and 14:1 were replicated in triplicate. The highest weight-gain rate(3 506±48)% and survival rate(89.38±0.88)% was observed in well water with Na/K ratios of 23:1 and 42:1, respectively, while the feed conversion ratio(1.02±0.01), oxygen consumption, and ammonia-N excretion rate was the lowest in the medium with a Na/K ratio of 23:1. Gill Na +-K +-ATPase activity, as an indicator of osmoregulation, peaked in the treatment where the Na/K ratio was 17:1. The total hemocyte count, respiratory burst, and immune-related enzyme activities(ALP, LSZ, PO, and SOD) of L. vananmei were affected significantly by Na/K ratios( P 0.05). After challenged with Vibrio harveyi, the cumulative mortality of shrimp reared in a Na/K ratio of 23:1(30±14.14)% was significantly lower than the control(75±7.07)%. In conclusion, the addition of K + to low-salinity well water in L. vannamei cultures is feasible. Na/K ratios ranging from 23:1 to 33:1 might improve survival and growth. Immunity and disease resistance are also closely related to the Na/K ratio of the low-salinity well water. The findings may contribute to the development of more efficient K + remediation strategies for L. vananmei culture in low-salinity well water. 相似文献
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