Measurement Errors and Imperfect Detection Rates on the Transect Line in Independent Observer Line Transect Surveys

Abstract Brown bear Ursus arctos population density was estimated for a 21,178-km2 study area in southwest Alaska. Estimates were obtained using an aerial line-transect method that allows for peak detection to be both off the transect line and less than 100%. Data collection required five small aircraft with 2-person crews. Surveys were flown in 10-d windows to capture the period after den emergence but prior to full green-up. Surveys were flown in two consecutive years in order to detect sufficient bear groups to support the estimation. The study detected 197 bear groups (330 bears) in 969 aerial transects averaging 24.8 km long and with a strip width of 728 m. Estimated population density in the study area was 40.4 bears/1,000 km2 (95% CI = 31.4–54.5); estimated density of independent bears was 27.3 bears/1,000 km2 (95% CI = 21.4–34.4). Assuming similar estimate precision, repeating the survey could detect population changes of approximately 38% or larger with a power of 80%. We find the method described here suitable for regions of relatively high bear population densities or detection rates.

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

Wildlife Research ◽

10.1071/wr07077 ◽

2008 ◽

Vol 35 (4) ◽

pp. 275 ◽

Cited By ~ 31

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.

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STRUKTUR DEMOGRAFI POPULASI Rhizophora apiculata DI KAWASAN INDUSTRI PERMINYAKAN PROVINSI RIAU

JURNAL PERIKANAN TROPIS ◽

10.35308/jpt.v5i2.1038 ◽

2018 ◽

Vol 5 (2) ◽

pp. 189

Author(s):

Syahrial Syahrial ◽

Dietriech G Bengen ◽

Tri Prartono ◽

Bintal Amin

Keyword(s):

Water Quality ◽

Sea Water ◽

Quality Parameters ◽

Line Transect ◽

Marine Biota ◽

Mangrove Forests ◽

Vegetation Density ◽

Transect Line ◽

Rhizophora Apiculata ◽

Mangrove Vegetation

The decline in mangrove vegetation density and the area of mangrove forests in the coastal province of Riau occurred due to the logging of mangrove forests and the conversion of mangrove forests into other uses such as industrial estates. This study aims to collect a database of mangrove ecosystems which includes the ecological structure of R. apiculata in Riau Province. Collecting data of mangrove vegetation condition was done by transect line and plot. The line transect was drawn from the reference point (the outer mangrove stand) with the direction perpendicular to the coastline to the mainland and made plots according to the category. The results showed that the population of R. apiculata was found in large numbers at Station 3 (350 ind) and a small/small amount was found at Station 1 (137 ind). In addition, Stations 1, 2 and 4 have only one grouping population of R. apiculata based on the Bhattacharya method, while Station 3 has two groupings. Furthermore, the highest R. apiculata density for tree category was obtained at Station 4 (1433.33 ind/m2), saplings category at Station 3 (10488.89 ind/m2) and seedlings category at Station 4 (3666667 ind/m2). Furthermore the water temperature ranged from 28.3 – 30.7°C, salinity 27.3 – 31.3, pH 7.3 – 7.9, DO 5.2 – 6.4 and redox potential ranged from 102 – 124 mV. Based on the standard criteria and guidelines for determining mangrove damage according to the Decree of the Minister of Environment No. 201 of 2004, the population density of R. apiculata at the research location is still classified as medium and refers to the Decree of the State Minister of Environment No. 51 of 2004 concerning Sea Water Quality Standards for Marine Biota, as a whole the range of measured water quality parameters is still within tolerance limits for life mangroves.

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Accounting for imperfect detection when evaluating the effectiveness of invasive species control

New Zealand Plant Protection ◽

10.30843/nzpp.2014.67.5782 ◽

2014 ◽

Vol 67 ◽

pp. 320-320

Author(s):

J.L. Moore ◽

E. Gurarie

Keyword(s):

Invasive Plant ◽

Plant Size ◽

Gps Tracking ◽

Imperfect Detection ◽

Detection Rates ◽

Invasive Species Control ◽

People Search ◽

Search And Destroy

Many invasive plant species are sparsely distributed across large areas Management of these species is often undertaken using a search and destroy approach where people search the landscape and treat (destroy) any individuals found However detection is imperfect and so these searches need to be undertaken on multiple occasions Given limited resources an explicit objective is to optimize efforts by targeting those areas for follow up visits that have the highest predicted abundance In order to simultaneously estimate both abundances and detection rates from data on search and destroy efforts it is necessary to have a good model of the detection process itself In a case study of invasive willow control across 120 km2 in alpine Australia intensively monitored sample plots were used to characterise how detection rates depend on perceived abundance for three groups of willow control contractors Bayesian models were used to fit an exponential detection function where the detection rate varied with plant size between contractors with the total number of willows treated and on features of the contractors movements It was found that detection rates decreased with increasing abundance but areas with high abundance were subject to greater search effort These models were combined with GPS tracking data representing 6 weeks of search and destroy missions to predict the remaining abundance of willows across the landscape and hence areas that are priorities for follow up control were identified

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Bird diversity analysis in the lower mountain forest of mount Bulusaraung to support ecotourism’s activities in Bantimurung Bulusaraung National Park

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/886/1/012047 ◽

2021 ◽

Vol 886 (1) ◽

pp. 012047

Author(s):

A Achmad ◽

U Damayanti ◽

R I Maulany

Keyword(s):

Species Diversity ◽

National Park ◽

Bird Species ◽

Diversity Indices ◽

Bird Diversity ◽

Line Transect ◽

Mountain Forest ◽

Transect Line ◽

Species Diversity Indices ◽

Evenness Indices

Abstract Lower mountain forest in the complex of Mount Bulusaraung Bantimurung Bulusaraung National Park, is a one of bird’s habitat in the South Sulawesi. This area is a tourist destination, especially mountain climbing activities. Thus, it is necessary to know the diversity of animals, especially birds on this hiking trail, so that the information can be used to support ecotourism activities. This study aims to analyze the diversity of bird species in the complex of Bulusaraung Mountain, Bantimurung Bulusaraung National Park in order to support ecotourism activities. This research was conducted from April to June 2018. Data was collected using the line transect method on three lines, namely the Balleanging, Kattokaddaro and Tompobulu lines. The second and third paths are hiking trails, while the rest are trails leading to community agricultural areas. The geographical position of the transect line was recorded using GPS. The GIS method was used to generate a bird watching trail map. Data analysis was carried out to calculate the individual density and frequency of bird presence. In addition, the species diversity indices, species evenness indices, and species richness indices were also calculated. The results showed that there were 44 species of birds found in the study area, which were 16 species in the Balleanging line, 27 species in the Kattokaddaro line and 37 species in the Tompobulu line. The highest bird species diversity indices value was found on the Tompobulu line (H' = 2.93), while on the Kattokaddaro line it was H' = 2.73 and the Balleanging H' = 2.55. The results of this study will support the management strategy in Bantimurung Bulusaraung National Park in order to harmonize the conservation of biological resources through ecotourism activities that involve local communities to increase their economic income.

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ANALISIS KERAPATAN MANGROVE SEBAGAI SALAH SATU INDIKATOR EKOWISATA DI PERAIRAN PANTAI DUSUN ALARIANO KECAMATAN AMAHAI KABUPATEN MALUKU TENGAH

JURNAL HUTAN PULAU-PULAU KECIL ◽

10.30598/jhppk.2019.3.2.217 ◽

2019 ◽

Vol 3 (2) ◽

pp. 217-266

Author(s):

Elsye M Nanulaitta ◽

Abraham H Tulalessy ◽

Deli Wakano

Keyword(s):

Species Density ◽

Line Transect ◽

Sample Plot ◽

Aegiceras Corniculatum ◽

Transect Line ◽

Rhizophora Apiculata ◽

Xylocarpus Granatum ◽

Bruguiera Gymnorhiza

This study aims to determine the type and density of mangroves on the coast of Alariano sub-village Amahai District, Central Maluku Regency. This research was carried out in May 2019. The research location was divided into 2 stations. this research is descriptive quantitative. The method used in this research is line transect and sample plot (Transect line plot. Based on the results of the study found 6 types of mangroves including Achantus ebracteatus, Aegiceras corniculatum, Sonnerattia alba, Bruguiera gymnorhiza, Rhizophora apiculata, Xylocarpus granatum. According to the standard criteria of mangrove damage. the results of the calculation of species density at station I and station II are categorized as very dense so that they can be potential for ecotourism development.

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Gastropod Density and Diversity in the Intertidal Zone of Malalayang Beach, Manado

JURNAL PERIKANAN DAN KELAUTAN TROPIS ◽

10.35800/jpkt.10.3.2019.27533 ◽

2020 ◽

Vol 10 (3) ◽

pp. 121

Author(s):

Sheyrel Tongkeles ◽

Fransine B. Manginsela ◽

Jety K. Rangan ◽

Alex D. Kambey

Keyword(s):

Intertidal Zone ◽

Diversity Index ◽

Line Transect ◽

Random Numbers ◽

Total Density ◽

Gastropod Species ◽

Transect Line ◽

Line Transects ◽

High Diversity

This study held in Malalayang Beach Manado, aims to determine the density and diversity of Gastropods on the Malalayang coast of Manado. So the research objective is to find out the density and diversity of Gastropods in Malalayang Beach, Manado. The study using the line transect technique with 50 cm x 50 cm sized. The transect line is placed perpendicular to the coastline. The distance between the line transects is 20 meters. On each transect line 5 squares are placed. The distance between squares is determined using random numbers. Gastropod species found in Malalayang Beach Manado consist of 31 species and 17 genus, each consisting of the Archaeogastropoda that consists of 3 species, Mesogastropoda consists of 9 species, and the Order of the Neogastropoda of 19 species. The total density of Gastropods in Malalayang Beach in Manado is 6.27 individuals / m2 with diversity of 3.07, according to the criteria for diversity index of Malalayang coast having high diversity. Based on this, it is suggested that Manado Malalayang Beach can be maintained and carried out management that considers the feasibility of the environment as one of the requirements for sustainable development.Keywords: Gastropods, Density, Species DiversityABSTRAK Penelitian ini dilakukan di Pantai Malalayang Manado,berkaitan dengan permasalahan yang dikemukakan bagaimanakah kepadatan dan keanekaragaman Gastropoda di pantai Malalayang Manado. Maka tujuan penelitian adalah Mengetahui kepadatan dan keanekaragaman Gastropoda di Pantai Malalayang Manado. Pengumpulan data dengan pendekatan Teknik line transect menggunakan kuadrat berukuran 50cm x 50cm. Line transect diletakkan tegak lurus dengan garis pantai. Jarak antara line transect sebesar 20 meter. Pada masing- masing line transect diletakkan 5 kuadrat. Jarak antar kuadrat ditentukan dengan menggunakan angka acak. Spesies Gastropoda yang ditemukan di Pantai Malalayang Manado terdiri dari 31 spesies dan 17 genera yang masing-masing terdiri dari Ordo Archaeogastropoda 3 spesies, Ordo Mesogastropoda 9 spesies, dan Ordo Neogastropoda 19 spesies. Kepadatan total Gastropoda di Pantai Malalayang Manado 6.27 individu/m2 dengan keanekaragaman 3,07, Menurut kriteria indeks keanekaragaman pantai Malalayang memiliki keanekaragaman yang tinggi. Berdasarkan hal tersebut, maka disarankan agar Pantai Malalayang Manado dapat dijaga dan dilakukan pengelolaan yang mempertimbangkan sskelayakan lingkungan sebagai salah satu syarat pembangunan berkelanjutan.Kata kunci: Gastropoda, Kepadatan, Keanekaragaman Jenis

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Conventional distance sampling versus strip transects and abundance indices for estimating abundance of greater gliders (Petauroides volans) and eastern ringtail possums (Pseudocheirus peregrinus)

Wildlife Research ◽

10.1071/wr18155 ◽

2019 ◽

Vol 46 (6) ◽

pp. 518

Author(s):

Luke D. Emerson ◽

Guy-Anthony Ballard ◽

Karl Vernes

Keyword(s):

Distance Sampling ◽

Probability Of Detection ◽

Density Estimate ◽

Imperfect Detection ◽

Density Estimates ◽

Transect Line ◽

Eucalypt Forest ◽

Arboreal Marsupials ◽

Abundance Indices ◽

Strip Transect

Abstract ContextAccurate estimates of abundance are extremely useful for wildlife management and conservation. Estimates generated from distance sampling are typically considered superior to strip transects and abundance indices, as the latter do not account for probability of detection, thereby risking significant error. AimTo compare density estimates generated from conventional distance sampling (CDS) of arboreal marsupials with strip transect density estimates and abundance indices. MethodsOff-track CDS and strip transects were used to estimate densities of P. volans and P. peregrinus across ~2.6km2 of remnant eucalypt forest at Mt Duval in north-eastern New South Wales. Key resultsCDS density estimates for P. volans (1.36ha−1, 95% confidence interval (CI) of 1.07–1.72ha−1) and P. peregrinus (0.28ha−1, 95% CI 0.22–0.35ha−1) were consistent with densities reported in other studies conducted in open eucalypt forests. A strip transect width of 40m for P. volans resulted in a collective set of values for density (1.35ha−1), error (s.e.±0.14), precision (cv 0.10) and 95% CI (1.07–1.62ha−1) closest to those associated with the CDS-generated density estimate (1.36ha−1, s.e.±0.15, cv 0.10, 95% CI 1.07–1.72ha−1). Strip widths of 10 to 40m resulted in density estimates for P. peregrinus closest to those generated through CDS, but much less precise. ConclusionsAlthough a 40-m wide strip transect provided a robust density estimate for P. volans at Mt Duval, this is unlikely to be consistent across different study areas. Strip transects provided less precise density estimates, or underestimated P. peregrinus density at Mt Duval, when compared with CDS density estimates. CDS should be favoured over strip transects or abundance indices for estimating P. volans and P. peregrinus abundance, because it is capable of providing more meaningful and robust abundance estimates by accounting for the probability of detection from the transect line across different habitats. ImplicationsResearchers, conservation managers and decision makers should be aware that common methods for assessing arboreal marsupial abundance have serious potential weaknesses. Thus, it would be prudent to invest in studies that address imperfect detection to improve the quality of monitoring data.

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Measurement Errors in Line Transect Surveys

Biometrics ◽

10.2307/2533844 ◽

1998 ◽

Vol 54 (3) ◽

pp. 899 ◽

Cited By ~ 25

Author(s):

Song Xi Chen

Keyword(s):

Measurement Errors ◽

Line Transect

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

Wildlife Research ◽

10.1071/wr07080 ◽

2008 ◽

Vol 35 (4) ◽

pp. 310 ◽

Cited By ~ 17

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.

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