...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Estuarine Coastal and Shelf Science >Can we estimate molluscan abundance and biomass on the continental shelf?
【24h】

Can we estimate molluscan abundance and biomass on the continental shelf?

机译：我们可以估计大陆架上的软体动物的丰度和生物量吗？

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Few empirical studies have focused on the effect of sample density on the estimate of abundance of the dominant carbonate-producing fauna of the continental shelf. Here, we present such a study and consider the implications of suboptimal sampling design on estimates of abundance and size-frequency distribution. We focus on a principal carbonate producer of the U.S. Atlantic continental shelf, the Atlantic surfclam, Spisula solidissima. To evaluate the degree to which the results are typical, we analyze a dataset for the principal carbonate producer of Mid-Atlantic estuaries, the Eastern oyster Crassostrea virginica, obtained from Delaware Bay. These two species occupy different habitats and display different lifestyles, yet demonstrate similar challenges to survey design and similar trends with sampling density. The median of a series of simulated survey mean abundances, the central tendency obtained over a large number of surveys of the same area, always underestimated true abundance at low sample densities. More dramatic were the trends in the probability of a biased outcome. As sample density declined, the probability of a survey availability event, defined as a survey yielding indices >125% or <75% of the true population abundance, increased and that increase was disproportionately biased towards underestimates. For these cases where a single sample accessed about 0.001-0.004% of the domain, 8-15 random samples were required to reduce the probability of a survey availability event below 40%. The problem of differential bias, in which the probabilities of a biased-high and a biased-low survey index were distinctly unequal, was resolved with fewer samples than the problem of overall bias. These trends suggest that the influence of sampling density on survey design comes with a series of incremental challenges. At woefully inadequate sampling density, the probability of a biased-low survey index will substantially exceed the probability of a biased-high index. The survey time series on the average will return an estimate of the stock that underestimates true stock abundance. If sampling intensity is increased, the frequency of biased indices balances between high and low values. Incrementing sample number from this point steadily reduces the likelihood of a biased survey; however, the number of samples necessary to drive the probability of survey availability events to a preferred level of infrequency may be daunting. Moreover, certain size classes will be disproportionately susceptible to such events and the impact on size frequency will be species specific, depending on the relative dispersion of the size classes. (C) 2017 Elsevier Ltd. All rights reserved.
机译：很少有经验研究集中在样本密度对大陆架主要碳酸盐生产动物群落丰度估计的影响上。在这里，我们提出这样的研究，并考虑次优采样设计对丰度和大小频率分布估计的影响。我们专注于美国大西洋大陆架的主要碳酸盐生产商，大西洋冲浪蛤，螺旋藻solidissima。为了评估结果的典型程度，我们分析了从特拉华湾获得的中大西洋河口主要碳酸盐生产商东部牡蛎Crassostrea virginica的数据集。这两个物种分别生活在不同的生境中，表现出不同的生活方式，但对调查设计提出了类似的挑战，并且抽样密度也呈现出类似的趋势。一系列模拟调查的均值中位数是在同一地区的大量调查中获得的集中趋势，在低样本密度下始终低估了真实的调查度。更显着的是有偏见的可能性的趋势。随着样本密度的下降，调查可用性事件（定义为调查得出的真实人口丰度的> 125％或<75％）的可能性增加，并且这种增加不成比例地偏向低估。对于这些情况，单个样本访问了大约0.001-0.004％的域，则需要8-15个随机样本才能将调查可用性事件的概率降低到40％以下。与总体偏倚问题相比，使用更少的样本解决了差异偏倚问题，即偏高的调查指数和偏低的调查指数的概率明显不相等。这些趋势表明，抽样密度对调查设计的影响伴随着一系列挑战。在抽样密度严重不足的情况下，偏低调查指数的概率将大大超过偏高指数的概率。平均而言，调查时间序列将返回估计不足真实存量的存量估计值。如果增加采样强度，则偏向索引的频率会在高值和低值之间平衡。从这一点开始，增加样本数将稳步降低调查偏倚的可能性；但是，将调查可用性事件的概率提高到优选的不频率水平所需的样本数量可能令人生畏。而且，某些尺寸等级将不成比例地易受此类事件的影响，并且对尺寸频率的影响将是特定于物种的，具体取决于尺寸等级的相对分散。 （C）2017 Elsevier Ltd.保留所有权利。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号