A combination line transect and capture-recapture sampling model for multiple observers in aerial surveys

1996 ◽  
Vol 3 (4) ◽  
pp. 311-327 ◽  
Author(s):  
Russell Alp�zar-Jara ◽  
Kenneth H. Pollock
Keyword(s):  
Line Transect ◽  
Aerial Surveys ◽  
Capture Recapture ◽  
Combination Line

scholarly journals The influence of animal mobility on the assumption of uniform distances in aerial line-transect surveys

2008 ◽  
Vol 35 (4) ◽  
pp. 275 ◽  
Author(s):  
Rachel M. Fewster ◽  
Colin Southwell ◽  
David L. Borchers ◽  
Stephen T. Buckland ◽  
Anthony R. Pople
Keyword(s):  
Survey Design ◽  
Distance Sampling ◽  
High Mobility ◽  
Line Transect ◽  
Transect Line ◽  
Aerial Surveys ◽  
Pack Ice ◽  
Capture Recapture ◽  
Distance Data ◽  
Crabeater Seals

Line-transect distance sampling is a widely used method for estimating animal density from aerial surveys. Analysis of line-transect distance data usually relies on a requirement that the statistical distribution of distances of animal groups from the transect line is uniform. We show that this requirement is satisfied by the survey design if all other assumptions of distance sampling hold, but it can be violated by consistent survey problems such as responsive movement of the animals towards or away from the observer. We hypothesise that problems with the uniform requirement are unlikely to be encountered for immobile taxa, but might become substantial for species of high mobility. We test evidence for non-uniformity using double-observer distance data from two aerial surveys of five species with a spectrum of mobility capabilities and tendencies. No clear evidence against uniformity was found for crabeater seals or emperor penguins on the pack-ice in East Antarctica, while minor non-uniformity consistent with responsive movement up to 30 m was found for Adelie penguins. Strong evidence of either non-uniformity or a failure of the capture–recapture validating method was found for eastern grey kangaroos and red kangaroos in Queensland.

scholarly journals An open spatial capture–recapture model for estimating density, movement, and population dynamics from line‐transect surveys

2021 ◽  
Author(s):  
Timothy A. Gowan ◽  
Nathan J. Crum ◽  
Jason J. Roberts
Keyword(s):  
Population Dynamics ◽  
Line Transect ◽  
Capture Recapture

Line Transect Sampling Under Varying Conditions with Application to Aerial Surveys

Ecology ◽  
1996 ◽  
Vol 77 (4) ◽  
pp. 1297-1302 ◽  
Author(s):  
Pham X. Quang ◽  
Earl F. Becker
Keyword(s):  
Line Transect ◽  
Line Transect Sampling ◽  
Aerial Surveys ◽  
Transect Sampling

Combining Line Transect and Double Count Sampling Techniques for Aerial Surveys

1997 ◽  
Vol 2 (2) ◽  
pp. 230 ◽  
Author(s):  
Pham X. Quang ◽  
Earl F. Becker
Keyword(s):  
Line Transect ◽  
Sampling Techniques ◽  
Aerial Surveys

Aerial surveys of multiple species: critical assumptions and sources of bias in distance and mark - recapture estimators

2008 ◽  
Vol 35 (4) ◽  
pp. 310 ◽  
Author(s):  
Gavin J. Melville ◽  
John P. Tracey ◽  
Peter J. S. Fleming ◽  
Brian S. Lukins
Keyword(s):  
Line Transect ◽  
Implicit Assumption ◽  
Distance Method ◽  
Mark Recapture ◽  
Transect Line ◽  
Aerial Surveys ◽  
Transect Sampling ◽  
Multiple Covariates ◽  
Recent Developments ◽  
Multiple Species

Recent developments in the application of line-transect models to aerial surveys have used double-observer sampling to account for undercounting on the transect line, a crucial step in obtaining correct population estimates. This method is commonly called the mark–recapture line-transect sampling method and estimates the detection probability at zero distance to correct line-transect estimates of abundance. An alternative approach, which uses the same methodology during data collection, is to use a range of covariates, including distance from the transect, in a mark–recapture model. This approach overcomes the implicit assumption of uniform distribution of distances in line-transect estimators. In this paper, we use three alternative approaches (a multiple-covariates distance method, a distance method incorporating adjustment for incomplete detection on the transect line using mark–recapture sampling, and a mark–recapture method with distance as a covariate) to estimate the abundance of several medium-sized mammals in semiarid ecosystems. Densities determined with the three estimators varied considerably within species and sites. In some cases distance estimates were larger than mark–recapture estimates and vice versa. Despite large numbers of observations, distance uniformity was not observed for any species at any site, nor for any species where sites were combined. Possible reasons, which include sampling variability, movement in response to the aircraft and failure of the mark–recapture independence assumption, are discussed in detail.

A Line Transect Model for Aerial Surveys

Biometrics ◽  
1991 ◽  
Vol 47 (3) ◽  
pp. 1089 ◽  
Author(s):  
Pham Xuan Quang ◽  
Richard B. Lanctot
Keyword(s):  
Line Transect ◽  
Aerial Surveys

scholarly journals Distribution and Abundance of Cetaceans in Icelandic Waters over 30 Years of Aerial Surveys

2020 ◽  
Vol 11 ◽  
Author(s):  
Daniel Pike ◽  
Thorvaldur Gunnlaugsson ◽  
Johann Sigurjonsson ◽  
Gisli Vikingsson
Keyword(s):  
Relative Abundance ◽  
Humpback Whales ◽  
Line Transect ◽  
Balaenoptera Acutorostrata ◽  
Aerial Surveys ◽  
Minke Whales ◽  
Abundance Estimates ◽  
Ecosystem Changes ◽  
Common Minke Whale ◽  
Icelandic Waters

Beginning in 1986, 7 aerial surveys covering the coastal waters of Iceland have been conducted up to 2016. In addition, several partial surveys covering portions of the same area and at different times of the year have been flown in the same 30 year time span. We present previously unpublished abundance estimates, corrected to the extent feasible for known biases, for common minke whales (Balaenoptera acutorostrata), humpback whales (Megaptera novaeangliae), white-beaked dolphins (Lagenorhynchus albirostris) and harbour porpoises (Phocoena phocoena) from some or all of the 2007, 2009 and 2016 surveys. The relative abundance of most species was comparatively low in the spring and fall, and peaked June and July when all of the main surveys have been carried out. An analysis of changes in line transect density as an index of relative abundance from all surveys indicates that common minke whale abundance decreased by 75% after 2001 and has remained at a relatively low level since then. Relative abundance of humpback whales and white-beaked dolphins has increased over the period 1986-2016. We place these observed changes in context with oceanographic and ecosystem changes documented over the same period.

scholarly journals Trends in the distribution and abundance of cetaceans from aerial surveys in Icelandic coastal waters, 1986-2001

2009 ◽  
Vol 7 ◽  
pp. 117 ◽  
Author(s):  
Daniel G Pike ◽  
Charles GM Paxton ◽  
Thorvaldur Gunnlaugsson ◽  
Gísli A Víkingsson
Keyword(s):  
Relative Abundance ◽  
Minke Whale ◽  
Humpback Whales ◽  
Line Transect ◽  
Survey Area ◽  
Balaenoptera Acutorostrata ◽  
The North ◽  
Aerial Surveys ◽  
Minke Whales ◽  
Abundance Estimates

Aerial surveys were carried out in coastal Icelandic waters 4 times between 1986 and 2001 as part of the North Atlantic Sightings Surveys. The surveys had nearly identical designs in 3 of the 4 years. The target species was the minke whale (Balaenoptera acutorostrata) but all species encountered were recorded. Sighting rate and density from line transect analysis were used as indices of relative abundance to monitor trends over the period, and abundance estimates corrected for perception biases were calculated for some species from the 2001 survey. More than 11 species were sighted, of which the most common were the minke whale, humpback whale (Megaptera novaeangliae), dolphins of genus Lagenorhychus, and the harbour porpoise (Phocoena phocoena). Minke whales anddolphins showed little change in distribution or abundance over the period. There were an estimated 31,653 (cv 0.30) dolphins in the survey area in 2001. Humpback whales increased rapidly at a rate of about 12%, with much of the increase occurring off eastern and northeastern Iceland. In 2001 there were an estimated 4,928 (cv 0.463) humpback whales in the survey area. The relative abundance of harbour porpoises decreased over the period, but estimates for this species were compromised by uncorrected perception biases and poor coverage. The ecological and historical significance of these findings with respect to previous whaling activities and present-day fisheries is discussed.

scholarly journals Application of an Ultralight Aircraft to Aerial Surveys of Kangaroos on Grazing Properties

1997 ◽  
Vol 24 (3) ◽  
pp. 359 ◽  
Author(s):  
G. C. Grigg ◽  
A. R. Pople ◽  
L. A. Beard
Keyword(s):  
Species Identification ◽  
Small Area ◽  
Aerial Survey ◽  
Accreditation Process ◽  
Line Transect ◽  
Future Scenario ◽  
Numerical Comparisons ◽  
Aerial Surveys

A Drifter ultralight aircraft was used as a platform for line-transect aerial surveys of three species of kangaroo in the sheep rangelands south-east of Blackall and north of Longreach in central-western Queensland in winter 1993 and 1994. Favourable comparisons between the results of ultralight surveys and those made from a helicopter flying the same transects and foot surveys along another set of transects, all within a few days of the ultralight survey, confirmed the expectation we had that an ultralight would be a satisfactory and much cheaper vehicle for conducting aerial surveys of kangaroos. The comparisons are even more favourable when data for the three species surveyed are combined, pointing to a problem in species identification and underlining the importance of using only experienced observers for aerial survey of kangaroos, whatever the platform. The use of an ultralight aircraft could have particular value where a comparatively small area, such as an individual sheep or cattle property, is under consideration. In this paper, we present the numerical comparisons, along with an evaluation of the practicability of using this type of aircraft. We also describe a possible future scenario in which an accreditation process could see approved kangaroo surveyors undertaking property assessments by ultralight, under contract to graziers or other interested parties.

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