共查询到20条相似文献，搜索用时 250 毫秒
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冰面水体是冰盖物质平衡的重要组成部分,在全球气候及环境变化研究中发挥着重要的作用。本文以格陵兰岛北部为研究区,选取该区域消融期内不同时相的WorldView-2影像,统计分析区域内典型地物光谱特性,构建了针对冰面水体的归一化水体增强指数NEWI (Normalized Enhanced Water Index);依据影像上地物分布规律和直方图图形特征,定位冰雪混合物和冰面水体边缘地带灰度值相似的模糊区域,增强区域间地物对比度,提取出冰面水体的精细范围。实验结果表明,本研究所构建的指数有效凸显了冰面水体与非水体的反射率差异。与常用的水体指数NDWI等相比,冰川环境下,本文指数在提高区分度方面优势明显。通过精度评价可知,本文方法所提取出的冰面水体精细化程度高、提取结果完整、错误率低。本研究对冰面水体信息增强及精细化提取具有重要指导意义。 相似文献
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为应对渔业资源的日益衰退,增殖放流成为了目前补充资源、维持资源可持续利用的主要手段之一。增殖放流实施后,渔业资源的可持续特征是学者们普遍关心,却又无法使用传统剩余产量模型有效解决的问题。本研究基于传统的Schaefer剩余产量模型,提出了一个适用于增殖放流情况下的剩余产量模型(增殖剩余产量模型),模拟分析了不同增殖放流和捕捞策略对模型的影响。该模型的形式与Schaefer剩余产量模型相似,但加入了描述增殖群体增长特征的参数—有效增殖率,以此来表示增殖放流的群体对产量产生的影响。结果显示,合理的增殖放流可以起到增加最大可持续产量的效果,使用增殖剩余产量模型能够得到合理的最大可持续产量等关键指标的估算结果。与无增殖放流情况相比,在增殖放流影响下,海域原存资源(海域原本存在的群体)达到最大可持续产量时所需的生物量较小,而可承受的捕捞努力量则有所增加。增殖剩余产量模型所反映的原存群体和增殖群体之间会产生抑制作用。在该作用影响下,不同增殖放流和捕捞策略会对模型的评估结果产生影响。与传统模型相比,该模型将增殖放流纳入最大可持续产量的评估过程,提高了增殖放流影响下最大可持续产量评估的准确性,可用于诸如海洋牧场等边界较清晰的海域内增殖定栖性种类最大可持续产量的估算。 相似文献
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Two methods,tagging and ink injection,are used in the grouper releasing experiment.The studied fishes are the juvenile of Epinephelus akaara and Epinephelus awoara both artificially cultivated and caught from natural waters,and their wild adults.Experimental results show that the inhabiting behaviours for both juvenile and adult fishes show distinct regionality,which move within an area of 2n mile diameter 651 days and 48 days after being released,respectively,With the tagging method,the tagged fishes could only be recaptured in the year of release while,with the injection method,they could be caught in the lst,2nd and 3rd years,It is confirmed that in the cement tank,the tagged fishes lose their 1/3 tags.That means that the tagging method is not fit for the release research while the injection method is .Generally,the recaptured rates of injected fishes are 1.4-4.5%,3.1-13.4%and 2.7%for the lst,1nd and 3rd years,respectively. 相似文献
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Enhancement effects of rare earth elements on the growth of Chaetoceros mulleri is studied in this paper. The results show that all of the light, middle and heavy rare earth elements have similar enhancement effect on the growth of Chaetoceros mulleri, with the beneficial concentrations of La, Gd and Yb being 7.28～87.40 μ mol/L, 6.36～57.23 μ mol/L and 5.78～17.34 μ mol/L. The optimum concentrations of La, Gd and Yb are 7.28 ～50.98 μ mol/L,31.80～44.52 μ m ol/L and 5.78～17.34 1μ mol/L, respectively. When the concentrations of La, Gd and Yb are 7.28～87.40 μ mol/L, 6.36～57.23 μ mol/L and 5.78～ 17,34 μ mol/L, the concentrations of chlorophyll have increased by 9.3～47.0%, 33.4～44.3%, and 36.5～40.3%, respectively as compared with the control group. The mechanism of enhancement of rare earth elements on the growth ot Chaetoceros mulleri is also discussed in this paper. 相似文献
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根据天津渤海水产研究所增殖放流资料,全面总结了天津市自2006来增殖放流工作的成效。天津市自2006年第一次开展以“中国对虾”为龙头的增殖放流活动,迄今为止,增殖品种已达22余种,其中以甲壳类占绝对优势。经过大规模增殖放流,天津市渔业资源增殖放流工作已取得了显著的生态、经济和社会效益。在文章最后,总结了国内外增殖放流的发展趋势,并提出了产业发展需求及发展目标。 相似文献
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I. M. Johnstone 《新西兰海洋与淡水研究杂志》2013,47(4):599-614
A concept of aquatic macrophyte management that integrates the positive and negative aspects of vegetation in lakes and rivers is discussed. This integrated approach involves three factors: macrophyte control, macrophyte enhancement, and identification and resolution of the conflicts created by multiple use of a waterbody. The primary decision in macrophyte management programmes must be whether to optimise for single‐purpose or for multipurpose use of the waterbody. Both technical (macrophyte control and enhancement) and social (conflict resolution) procedures are required to solve problems associated with the macrophyte status of multipurpose waterbodies. 相似文献
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J. D. Green 《新西兰海洋与淡水研究杂志》2013,47(2):199-222
Lake Ototoa is a warm monomictic lake at 36° 31’ S, 174° 14'E. During a year's study (March 1969‐March 1970), the lake became thermally stratified in November, the metalimnion being between depths of 12 m and 16 m. Surface temperatures ranged between 10.2°c (in August) and 25.2°c (in late January), and bottom temperatures between 9.7°c and 17.5°c. The annual heat budget was calculated to be 642 354 KJ.m‐2 (15 500 cal.cm‐2) and the work of the wind in distributing the heat income 1.730 KJ.m‐2 (1766 g.cm.cm‐2). Secchi disc transparencies ranged between 5 m and 9.2 m (mean 7.07 m) and were greatest in the summer. Light transmission per metre was also high, ranging between 61% and 87%. Surface waters were normally supersaturated with oxygen, but during summer stratification oxygen concentrations in the bottom waters dropped to a minimum of 2.3 mg.litre‐2 and a positive heterograde distribution of oxygen with depth was found. The oxygen deficit was 0.015 mg.cm‐2.day‐1 and showed the lake to be oligotrophic. Mean surface pH was 7.82, and the ionic composition of the waters was similar to that of other small New Zealand and Australian lakes located near the sea. Compared with other New Zealand lakes PO4‐P concentrations (range 1.00–10.20 μg.litre‐1) were low and NO3—N concentrations (range 0.12–0.60 mg.litre‐1) high. 相似文献
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Between March 1961 and January 1963 trawling surveys were carried out in the Bay of Plenty. Seasonal comparisons of catch weight were made for the four commercially important species, snapper, tarakihi, trevally, and gurnard, during 1962–63. Only trevally showed any marked seasonal variation in total catch. Tarakihi were most abundant in waters over 50 fathoms and snapper, trevally, and gurnard were most abundant in shallower depths. The best return for fishing effort came from the middle sector of the Bay. There was a marked absence of undersized tarakihi and trevally from the catches. A species composition list for the Bay of Plenty waters and a table of species abundance at the stations sampled has been compiled from the trawl catch data. 相似文献
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镧-氨基酸络合物对球等鞭金藻的影响 总被引：3，自引：0，他引：3
本文首次研究了镧-脯氨酸和镧-苯丙氨酸络合物对球等鞭金藻(Isochrysis galbana)的影响,结果表明,两种络合物对球等鞭金藻细胞繁殖及叶绿素的合成有明显的促进作用,浓度范围为5-20mg/dm3时,至第6天细胞数分别提高10.8%～17.2%,11.5%-20.5%(P<0.05);叶绿素浓度分别提高31.7%-37.5%,44.7%～48.4%(P<0.05),其中以浓度为10mg/dm3的实验组最高。镧的氨基酸络合物对球等鞭金藻的作用效果与镧相比是等同的。 相似文献
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HY-1/COCTS波段信息含量与波段相关性分析--以辽东湾为例 总被引：2，自引：0，他引：2
以2003年4月辽东湾的HY-1／COCTS数据为例,采用主成分分析法和相关分析法,从光谱的不同结构、主成分、相关性等方面来揭示COCTS图像的光谱信息。COCTS的10个波段中,9,10两个波段与其他几个波段相比,包含的信息较丰富。在其他的8个波段中,6,7波段的信息较为丰富,6波段对主成分的贡献大。这8个波段与9波段和10波段的相关性为负相关,表明它们间的重叠少。5波段与1波段、7波段与6波段、6波段与2波段的相关性较高,这说明这些数据间的彼此重叠较多,故在进行波段图像的假彩色合成时一般以8,4,3或8,4,1波段的组合为佳。以OIF指数来检查融合方法的可行性。 相似文献
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