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Estimating Abundance (estimating + abundance)

Distribution by Scientific Domains

Life Sciences	33%

Selected Abstracts

Estimating Abundance Using Mark,Resight When Sampling Is with Replacement or the Number of Marked Individuals Is Unknown

BIOMETRICS, Issue 1 2009
Brett T. McClintock
Summary Although mark,resight methods can often be a less expensive and less invasive means for estimating abundance in long-term population monitoring programs, two major limitations of the estimators are that they typically require sampling without replacement and/or the number of marked individuals available for resighting to be known exactly. These requirements can often be difficult to achieve. Here we address these limitations by introducing the Poisson log and zero-truncated Poisson log-normal mixed effects models (PNE and ZPNE, respectively). The generalized framework of the models allow the efficient use of covariates in modeling resighting rate and individual heterogeneity parameters, information-theoretic model selection and multimodel inference, and the incorporation of individually unidentified marks. Both models may be implemented using standard statistical computing software, but they have also been added to the mark,recapture freeware package Program MARK. We demonstrate the use and advantages of (Z)PNE using black-tailed prairie dog data recently collected in Colorado. We also investigate the expected relative performance of the models in simulation experiments. Compared to other available estimators, we generally found (Z)PNE to be more precise with little or no loss in confidence interval coverage. With the recent introduction of the logit-normal mixed effects model and (Z)PNE, a more flexible and efficient framework for mark,resight abundance estimation is now available for the sampling conditions most commonly encountered in these studies. [source]

Advanced Distance Sampling: Estimating Abundance of Biological Populations Edited by S. T. Buckland, D. R. Anderson, K. P. Burnham, J. L. Laake, D. L. Borchers, and L. Thomas

BIOMETRICS, Issue 3 2006
Russell Alpizar-Jara
No abstract is available for this article. [source]

Distribution and abundance of West Greenland humpback whales (Megaptera novaeangliae)

JOURNAL OF ZOOLOGY, Issue 4 2004
Finn Larsen
Abstract Photo-identification surveys of humpback whales Megaptera novaeangliae were conducted at West Greenland during 1988,93, the last 2 years of which were part of the internationally coordinated humpback whale research programme YoNAH, with the primary aim of estimating abundance for the West Greenland feeding aggregation. The area studied stretched from the coast out to the offshore margin of the banks, determined approximately by the 200 m depth contours, between c. 61°70,N and c. 66°N. The surveys were conducted between early July and mid-August and 993 h were expended on searching effort. A total of 670 groups of humpback whales was encountered leading to the identification of 348 individual animals. Three areas of concentration were identified: an area off Nuuk; an area at c. 63°30,N; and an area off Frederikshåb. Sequential Petersen capture,recapture estimates of abundance were calculated for five pairs of years at 357 (1988,89), 355 (1989,90), 566 (1990,91), 376 (1991,92), and 348 (1992,93). Excluding the anomalously high estimate in 1990,91, the simple mean is 359 (se= 27.3, CV = 0.076) and the inverse CV-squared weighted mean is 356 animals (se= 24.9, CV = 0.070). These calculations lead us to conclude that between 1988 and 1993 there were 360 humpbacks (CV = 0.07) in the West Greenland feeding aggregation. Using the Cormack,Jolly,Seber model framework non-calf survival rate was estimated at 0.957 (se= 0.028). Our data have low power (P < 0.3) to detect a trend of 3.1%, assuming the probability of a type I error was 0.05. [source]

Application of resazurin for estimating abundance of contaminant-degrading micro-organisms

LETTERS IN APPLIED MICROBIOLOGY, Issue 5 2001
Guerin
Aims: The aim of the current study was to test whether resazurin changed colour when incubated with a range of organic chemicals used as growth substrates in bioremediation studies and to determine whether resazurin was more effective in estimating microbial growth than turbidity alone (i.e. no resazurin) or use of the dye, methylene blue. Methods and Results: Resazurin was incubated with a range of organic chemicals that were used as substrates in an MPN assay. Only 1,2-dichlorobenzene, 2,4- D, glycol sulphite and sulphinol reacted to generate false positives. Resazurin was also used to estimate micro-organisms in a series of bioremediation studies. Conclusions: The results showed that resazurin was more sensitive than methylene blue or turbidity alone as an indicator of microbial growth. Significance and Impact of the Study: The significance of the current study is that resazurin should be used in MPN assays for estimating contaminant-degrading micro-organisms instead of turbidity alone or other dyes such as methylene blue. [source]

Double-Observer Line Transect Methods: Levels of Independence

BIOMETRICS, Issue 1 2010
Stephen T. Buckland
Summary Double-observer line transect methods are becoming increasingly widespread, especially for the estimation of marine mammal abundance from aerial and shipboard surveys when detection of animals on the line is uncertain. The resulting data supplement conventional distance sampling data with two-sample mark,recapture data. Like conventional mark,recapture data, these have inherent problems for estimating abundance in the presence of heterogeneity. Unlike conventional mark,recapture methods, line transect methods use knowledge of the distribution of a covariate, which affects detection probability (namely, distance from the transect line) in inference. This knowledge can be used to diagnose unmodeled heterogeneity in the mark,recapture component of the data. By modeling the covariance in detection probabilities with distance, we show how the estimation problem can be formulated in terms of different levels of independence. At one extreme, full independence is assumed, as in the Petersen estimator (which does not use distance data); at the other extreme, independence only occurs in the limit as detection probability tends to one. Between the two extremes, there is a range of models, including those currently in common use, which have intermediate levels of independence. We show how this framework can be used to provide more reliable analysis of double-observer line transect data. We test the methods by simulation, and by analysis of a dataset for which true abundance is known. We illustrate the approach through analysis of minke whale sightings data from the North Sea and adjacent waters. [source]