Size Bias in Line Transect Sampling: a Field Test
نویسنده
چکیده
An important problem in line tranaec\"'ia1iitillin. i. t.ba"t objects or point •. :..':; ',;,. ":':...; ..... ..; .';::"..~:. :..r..:.:...:,:.,,:: ..;.:...... ';,.:':":::'=:;.: ~,," , . clusters of objects of different m.fI. have .ditt~req~:JlicllfJng probabilities. In a recent paper Drummer and McDonsld (1987) develop a bivariate sighting function. Their function is dependent.-on·1erPendic~lardistance and object size. One important special case i:s .~._ex~C!nsion ot 'the exponential power J series sighting function first proposed'-by Pollock (1978). In this note ,. empirical evidence is given for this mOdel based on-a' field test ot line transect sampling theory. Beer cans we1"!L:!J.sed to simulate point clusters of objects with 1, 2, 4 and 8 cluster sizes.
منابع مشابه
The Effect of Animal Movement on Line Transect Estimates of Abundance
Line transect sampling is a distance sampling method for estimating the abundance of wild animal populations. One key assumption of this method is that all animals are detected at their initial location. Animal movement independent of the transect and observer can thus cause substantial bias. We present an analytic expression for this bias when detection within the transect is certain (strip tr...
متن کاملPerformance of transect and point count underwater visual census methods
A simulation approach was used to study bias and variability of density estimates of fish using the transect and point count underwater visual census methods. Three experiments were conducted to examine the effects of fish density, sampling effort, and the speed of fish in relation to the observer. Fish density and sampling effort did not significantly bias estimates of fish density using eithe...
متن کاملPredicting and correcting bias caused by measurement error in line transect sampling using multiplicative error models.
Line transect sampling is one of the most widely used methods for animal abundance assessment. Standard estimation methods assume certain detection on the transect, no animal movement, and no measurement errors. Failure of the assumptions can cause substantial bias. In this work, the effect of error measurement on line transect estimators is investigated. Based on considerations of the process ...
متن کاملOptimizing line intercept sampling and estimation for feral swine damage levels in ecologically sensitive wetland plant communities.
Ecological sampling can be labor intensive, and logistically impractical in certain environments. We optimize line intercept sampling and compare estimation methods for assessing feral swine damage within fragile wetland ecosystems in Florida. Sensitive wetland sites, and the swine damage within them, were mapped using GPS technology. Evenly spaced parallel transect lines were simulated across ...
متن کاملLine transect sampling from a curving path.
Cutting straight line transects through dense forest is time consuming and expensive when large areas need to be surveyed for rare or highly clustered species. We argue that existing paths or game trails may be suitable as transects for line transect sampling even though they will not, in general, run straight. Formulas and software currently used to estimate local density using perpendicular d...
متن کامل