Line-Transect
Using hidden Markov models to deal with availability bias on line transect surveys
... from line transect (LT) surveys of animals that are not always available for detection while within de- tectable range are subject to negative bias if animal availabil- ity is not accounted ...
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Review of potential line transect methodologies for estimating abundance of dolphin stocks in the eastern tropical Pacific
... Line transect surveys conducted by the NMFS in the ETP began in 1974 using a combination of aircraft and ships (Smith, 1981; Holt and Powers, ...lay transect segments strictly at ...
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Designing a shipboard line transect survey to estimate cetacean abundance off the Azores Archipelago, Portugal
... Line transect surveys are commonly applied to wildlife populations or natural resources, as they provide a cost efficient manner of dealing with mobile populations that may be sparse over a large region ...
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Double observer line transect surveys with Markov modulated Poisson process models for animal availability
... for line transect surveys in which animals go undetected at distance zero, either because they are stochastically unavailable while within view or because they are missed when they are avail- ...the ...
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Accommodating availability bias on line transect surveys using hidden Markov models
... on line transect surveys. Line transect methods are well developed for situations in which animals are detected with certainty at zero ...recapture line transect (MRLT) methods ...
13
Methods for estimating sperm whale abundance from passive acoustic line transect surveys
... An alternative is to use ˆ N obs only to estimate mean school size, and to use conventional line transect methods on schools to estimate school abundance. If schools are readily identifiable (using some ...
16
Humpback whale Megaptera novaeangliae (Cetartiodactyla: Balaenopteridae) group sizes in line transect ship surveys : an evaluation of observer errors
... that estimates of cetacean group sizes may have high variance among different observers, even when made from the same ship. The main source of error in those cases were the particu- lar characteristics of observer’s ...
5
Design and analysis of line transect surveys for primates
... the line transect ...the line transect ...the line transect survey; variation in size and spread by time of day, season or other factors (Plumptre, 2000) will be controlled ...
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An Adaptation of Kernel Density Estimation for Population Abundance using Line Transect Sampling When the Shoulder Condition is Violated
... Line transect technique is an easy approach that is used in practice to estimate population abundance, D , in line transect ...the line transect sampling is distributed as ...
5
Double observer line transect methods : levels of independence
... In line transect sampling, an observer travels along each of a number of lines, laid out according to some randomised (usually systematic random) scheme, and records each detected animal, together with its ...
27
The effect of animal movement on line transect estimates of abundance
... Conceptually, line transect sampling is a snapshot method [1] (pp. 31), that is, we consider that the animals are at a fixed location while the survey takes place. Thus, we have probabilistic en- counters ...
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Global coverage of cetacean line transect surveys : status quo, data gaps and future challenges
... cetacean line- transect surveys, often producing several estimates for the same species based on the same data pooled or analysed in different ways and across different time periods or areas complicates ...
13
Modeling distribution and abundance of Antarctic baleen whales using ships of opportunity
... design-unbiased line transect surveys may be simply out of reach for researchers in many countries, which nonetheless grapple with problems of conservation of endangered species, by-catch of small cetaceans ...
28
Distance sampling detection functions : 2D or not 2D?
... 2D line transect estimator can be seen as kind of removal method estimator, and that removal methods do not work well unless a large fraction of the population is removed, we believe these methods should be ...
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Animal Counting Toolkit : a practical guide to small boat surveys for estimating abundance of coastal marine mammals
... ABSTRACT: Small cetaceans (dolphins and porpoises) face serious anthropogenic threats in coastal habitats. These include bycatch in fisheries; exposure to noise, plastic and chemical pollution; distur- bance from ...
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State space approach to evaluate spatial variability of field measured soil water status along a line transect in a volcanic vesuvian soil
... Abstract. Unsaturated hydraulic properties and their spatial variability today are analyzed in order to use properly math- ematical models developed to simulate flow of the water and solute movement at the field-scale ...
9
Global analysis of cetacean line transect surveys : detecting trends in cetacean density
... visual line-transect surveys associ- ated with a clearly defined survey area, allowing estimates of abundance to be converted to densities (see below) and trends in density to be ...on ...
14
Estimating bird abundance : making methods work
... If an observer can reach a point without scaring birds away, he or she can wait a while before recording commences, to allow birds to return to their normal activities or original locations. This is called using a ...
18
Methods for investigating measurement error in cetacean line transect surveys
... Line-transect estimates of abundance generally assume that distances and angles to animals are measured without error. Biased distance measurements will lead to corresponding bias in abundance estimates. ...
8
Population status of Pan troglodytes verus in Lagoas de Cufada Natural Park, Guinea Bissau
... using line transect surveys [15,18,49,50], during which all the nests visible from the transect line are counted either individually [17,45] or in groups [23], or both ...same transect, ...
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