Combining Line Transect and Double Count Sampling Techniques for Aerial Surveys

Quang, Pham Xuan; Becker, Earl F.

doi:10.2307/1400405

Cited by 39 publications

(30 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The assumption that g(0) = 1 is often false and new methods have been developed to avoid this assumption. For example, Quang and Becker (1997) combine the line transect with double count sampling techniques in aerial surveys and use the double count to estimate the maximum of g(y), which will generally not occur at y = 0, by fitting a Weibull curve to g(y). Laake et al (1997), using a team of observers and appropriate models, actually estimated g(0) and found it to be considerably less than one.…”

Section: Quadrat and Strip Transectsmentioning

confidence: 99%

Estimating Animal Abundance: Review III

Schwarz¹,

Seber²

1999

Statist. Sci.

416

105

View full text Add to dashboard Cite

show abstract

Section: Quadrat and Strip Transectsmentioning

confidence: 99%

Estimating Animal Abundance: Review III

Schwarz¹,

Seber²

1999

Statist. Sci.

416

105

View full text Add to dashboard Cite

show abstract

“…We evaluate potential detection biases by applying a Petersen markrecapture estimator to the counts from the doublephotographic observations used in the aerial survey of 2012. A multiple-observer method based on markrecapture models is often used in aerial surveys with line-transect distance-sampling (Quang & Becker 1997, Buckland et al 2010 or strip transect sampling (Marsh & Sinclair 1989, Pollock et al 2006 but the application of this method to ice-breeding seals such as Caspian seals is new. Quantification of the recapture estimator allows a correction factor to be applied to directly observed counts, thereby allowing for 'missed' observations.…”

Section: Introductionmentioning

confidence: 99%

Inter-year variation in pup production of Caspian seals Pusa caspica 2005–2012 determined from aerial surveys

Dmitrieva¹,

Härkönen²,

Baimukanov³

et al. 2015

Endang. Species. Res.

View full text Add to dashboard Cite

Assessing species abundance and reproductive output is crucial for evaluations of population dynamics, conservation status and the development of management objectives. The Caspian seal Pusa caspica is a key predator in the Caspian Sea ecosystem and is listed as Endangered by the IUCN. Here we report on fixed-wing aerial strip transect surveys of the breeding population on the Caspian Sea winter ice field carried out in February, 2005−2012. Potential detection biases were estimated by applying a Petersen mark-recapture estimator to the counts from double photographic observations. We also tested for effects of weather conditions on count results, and for correlations between pup production and ice conditions and net primary productivity (npp). Fluctuations in pup production estimates were observed among years, ranging from 8200 pups (95% CI: 7130−9342) in 2010 to 34 000 (95% CI: 31 275−36 814) in 2005. Total adults on the ice ranged from 14 500 in 2010 to 66 300 in 2012. We did not detect significant associations between pup production and either ice summary data (ice season length and ice area) or npp. The observed inter-year variation may be partly due to underlying biological drivers influencing the fecundity of the population, although measurement errors arising from observation bias, plus variation in survey timing and weather conditions may also have contributed. Identifying the potential drivers of Caspian seal population dynamics will require extending both the survey time series and the quality of supporting data. However, inter-year fluctuations should still cause concern that the population may be vulnerable to environmental variability and ecosystem dynamics.

show abstract

“…Applying group-specific correction factors to observed animal groups can compensate for effects of detection bias when estimating abundance and composition. There are several methods for estimating group-specific detection probabilities in aerial surveys, including sightability models (Steinhorst and Samuel, 1989), distance models (Burnham and Anderson, 1984;Buckland et al, 2004), mark-resight models (White, 1996;Skalski et al, 2005), double-observer models (Graham and Bell, 1989), and methods that combine two or more such techniques often referred to as ''hybrid'' models (Quang and Becker, 1997;Buckland et al, 2010;Burt et al, 2014). These techniques all have individual strengths and weaknesses (Griffin et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Application of a hybrid model to reduce bias and improve precision in population estimates for elk (Cervus elaphus) inhabiting a cold desert ecosystem

Schoenecker

Lubow

2016

Journal of King Saud University - Science

View full text Add to dashboard Cite

Accurately estimating the size of wildlife populations is critical to wildlife management and conservation of species. Raw counts or ''minimum counts'' are still used as a basis for wildlife management decisions. Uncorrected raw counts are not only negatively biased due to failure to account for undetected animals, but also provide no estimate of precision on which to judge the utility of counts. We applied a hybrid population estimation technique that combined sightability modeling, radio collar-based mark-resight, and simultaneous double count (double-observer) modeling to estimate the population size of elk in a high elevation desert ecosystem. Combining several models maximizes the strengths of each individual model while minimizing their singular weaknesses. We collected data with aerial helicopter surveys of the elk population in the San Luis Valley and adjacent mountains in Colorado State, USA in 2005 and 2007. We present estimates from 7 alternative analyses: 3 based on different methods for obtaining a raw count and 4 based on different statistical models to correct for sighting probability bias. The most reliable of these approaches is a hybrid double-observer sightability model (model M H ), which uses detection patterns of 2 independent observers in a helicopter plus telemetry-based detections of radio collared elk groups. Data were fit to customized mark-resight models with individual sighting covariates. Error estimates were obtained by a bootstrapping procedure. The hybrid method was an improvement over commonly used alternatives, with improved precision compared to sightability modeling and reduced bias compared to double-observer modeling. The resulting population estimate corrected for multiple

show abstract

Combining Line Transect and Double Count Sampling Techniques for Aerial Surveys

Cited by 39 publications

References 20 publications

Estimating Animal Abundance: Review III

Estimating Animal Abundance: Review III

Inter-year variation in pup production of Caspian seals Pusa caspica 2005–2012 determined from aerial surveys

Application of a hybrid model to reduce bias and improve precision in population estimates for elk (Cervus elaphus) inhabiting a cold desert ecosystem

Contact Info

Product

Resources

About