Correcting for Visibility Bias in Strip Transect Aerial Surveys of Aquatic Fauna

1989 ◽  
Vol 53 (4) ◽  
pp. 1017 ◽  
Author(s):  
H. Marsh ◽  
D. F. Sinclair
Keyword(s):  
Aquatic Fauna ◽  
Aerial Surveys ◽  
Strip Transect

scholarly journals Estimated pup production of harp seals Pagophilus groenlandicus in the White Sea, Russia, in 2000

2003 ◽  
Vol 60 (5) ◽  
pp. 1012-1017 ◽  
Author(s):  
V.A Potelov ◽  
A.P Golikov ◽  
V.A Bondarev
Keyword(s):  
Standard Error ◽  
White Sea ◽  
Survey Design ◽  
The White Sea ◽  
Adult Females ◽  
Aerial Surveys ◽  
Pagophilus Groenlandicus ◽  
The 1960S ◽  
Adult Abundance ◽  
Strip Transect

Abstract Since the 1960s pup production of harp seals Pagophilus groenlandicus in the White Sea was estimated from aerial photographic surveys of visible adult females on the ice. Adult abundance estimations were underestimated because an unknown number of females were in the water during the survey. The absence of a reliable estimation of pup production constrained management initiatives. Aerial photographic surveys of whelping harp seals were conducted in the White Sea 10–12 March 2000. Using a systematic strip transect survey design approach, the number of pups present was estimated as 294 914 with a standard error (s.e.) of 36 168. When pups caught by Russian sealers in the White Sea before the aerial surveys (30 729 pups) were included the total estimated number of pups was 325 643 (s.e. 36 168), whereas the number of adult harp seals was 215 943 (s.e. 22 630). The pup estimate was not corrected for pups born after the survey, but this was not considered to be significant. The new estimation of pup production is higher than thought earlier.

scholarly journals Pilot aerial study of the marine megafauna in northern coast Alagoas, Brazil

2013 ◽  
Vol 41 (1-2) ◽  
Author(s):  
Maria Danise de Oliveira ALVES ◽  
João Carlos Gomes BORGES ◽  
Maria Elisabeth De ARAÚJO
Keyword(s):  
Sea Turtles ◽  
Water Clarity ◽  
Aerial Survey ◽  
Northern Coast ◽  
Sampling Area ◽  
Turbid Waters ◽  
Aerial Surveys ◽  
Low Visibility ◽  
Marine Megafauna ◽  
Strip Transect

This study aimed to investigate the feasibility of strip-transect aerial survey for the study of the marine megafauna in northern coast of Alagoas, chosen as the pilot area due to the better water clarity and the occurrence of the Antillean manatee. It was sighted 15 dolphins, 13 sea turtles and 10 manatees. From five aspects tested on the experimental flight, three adjustments were necessary on the methodology as following: 1) reduction of the transect angle to 40º to increase the sampling area; 2) constant transects of 1.5 nautical miles from shore to standardize the area of coverage; and 3) transects restricted to the mouths of estuaries due to low visibility in turbid waters. This study demonstrated the effectiveness of aerial surveys for the detection of marine megafauna. However, the adjustments proposed are necessary to minimize the characteristic limitations of each species and/or habitat. Keywords: aerial method, manatees, dolphins, sea turtles, limitations

Aerial survey of the dugong (Dugong dugon Muller 1776) in coastal waters of the Lease Islands, East Inodonesia

1995 ◽  
Vol 46 (4) ◽  
pp. 759 ◽  
Author(s):  
HH de Iongh ◽  
R Wenno ◽  
B Bierhuizen ◽  
B van Orden
Keyword(s):  
Coastal Waters ◽  
Aerial Survey ◽  
Neonatal Calf ◽  
Aerial Surveys ◽  
Coastal Shelf ◽  
Strip Transect

During December 1990 and August 1992, aerial surveys of dugongs were made along the coastlines of the Lease Islands in East Indonesia. The aerial surveys followed a strip transect covering the coastal shelf and totalled 3.5 h of observation. During the first survey, 17 dugongs were observed, one of which was a neonatal calf; during the second survey, 10 dugongs were seen but no neonates. The minimum population of dugongs was estimated to be between 22 and 37 animals. The population probably interacts with a larger unidentified reservoir of dugongs in the coastal waters of nearby Seram and Buru Islands.

Distribution and Abundance of Belugas, Delphinapterus leucas, and Narwhals, Monodon monoceros, in the Canadian High Arctic

1985 ◽  
Vol 42 (4) ◽  
pp. 676-684 ◽  
Author(s):  
T. G. Smith ◽  
M. O. Hammsll ◽  
D. J. Burrage ◽  
G. A. Sleno
Keyword(s):  
Scientific Literature ◽  
High Arctic ◽  
Delphinapterus Leucas ◽  
Confidence Limits ◽  
Canadian High Arctic ◽  
Monodon Monoceros ◽  
Aerial Surveys ◽  
Strip Transect

Opportunistic reconnaissance aerial surveys of Lancaster Sound, Barrow Strait, Peel Sound, and Prince Regent Inlet were conducted between 1974 and 1982 to determine the distribution and abundance of belugas, Delphinapterus leucas, and narwhals, Monodon monoceros. In 1981, two stratified strip-transect surveys were flown. From these we estimate that a total of 6300 – 18 600 belugas and approximately 13 200 –18 000 narwhals summer in Lancaster Sound and adjoining waterways. Improvement in the precision of these estimates would require a substantial increase in survey coverage and may not be justified considering the significant increase in costs. Our review of the results of surveys conducted since 1975 in the same study area, of which most of the information is not yet available in the scientific literature, shows much duplication of effort, little increase in information, and a lack of confidence limits for the estimated numbers.

scholarly journals Population estimates of Antillean manatees in Puerto Rico: an analytical framework for aerial surveys using multi-pass removal sampling

2019 ◽  
Vol 100 (4) ◽  
pp. 1340-1349
Author(s):  
Jaime A Collazo ◽  
Matthew J Krachey ◽  
Kenneth H Pollock ◽  
Francisco J Pérez-Aguilo ◽  
Jan P Zegarra ◽  
...  
Keyword(s):  
Puerto Rico ◽  
Detection Probability ◽  
Analytical Framework ◽  
Population Estimates ◽  
High Concentration ◽  
Imperfect Detection ◽  
Factors Affecting ◽  
Management Actions ◽  
Aerial Surveys ◽  
Population Size Estimates

AbstractEffective management of the threatened Antillean manatee (Trichechus manatus manatus) in Puerto Rico requires reliable estimates of population size. Estimates are needed to assess population responses to management actions, and whether recovery objectives have been met. Aerial surveys have been conducted since 1976, but none adjusted for imperfect detection. We summarize surveys since 1976, report on current distribution, and provide population estimates after accounting for apparent detection probability for surveys between June 2010 and March 2014. Estimates in areas of high concentration (hotspots) averaged 317 ± 101, three times higher than unadjusted counts (104 ± 0.56). Adjusted estimates in three areas outside hotspots also differed markedly from counts (75 ± 9.89 versus 19.5 ± 3.5). Average minimum island-wide estimate was 386 ± 89, similar to the maximum estimate of 360 suggested in 2005, but fewer than the 700 recently suggested by the Puerto Rico Manatee Conservation Center. Manatees were more widespread than previously understood. Improving estimates, locally or island-wide, will require stratifying the island differently and greater knowledge about factors affecting detection probability. Sharing our protocol with partners in nearby islands (e.g., Cuba, Jamaica, Hispaniola), whose populations share genetic make-up, would contribute to enhanced regional conservation through better population estimates and tracking range expansion.El manejo efectivo del manatí antillano amenazado en Puerto Rico requiere estimados de tamaños de poblaciónes confiables. Dichas estimaciones poblacionales son necesarias para evaluar las respuestas a las acciones de manejo, y para determinar si los objetivos de recuperación han sido alcanzados. Se han realizado censos aéreos desde 1976, pero ninguno de ellos han sido ajustados para detecciones imperfectas. Aquí resumimos los censos desde 1976, actualizamos la distribución, y reportamos los primeros estimados poblacionales ajustados para la probabilidad de detección aparente en los censos de Junio 2010 a Marzo 2014. Las estimaciones poblacionales en áreas de mayor concentración del manatí promedió 317 ± 103, tres veces más abundante que los conteos sin ajuste (104 ± 0.56). Las estimaciones poblacionales en tres áreas fuera de las áreas de mayor concentración del manatí también fueron marcadamente diferentes (75 ± 9.89 vs 19.5 ± 3.5). El estimado mínimo poblacional en la isla entera fue de 386 ± 89, similar al estimado máximo de 360 sugerido en el año 2005, pero menor a los 700 sugeridos recientemente por el Centro de Conservación de Manatíes de Puerto Rico. Documentamos que el manatí tiene una distribución más amplia de lo que se sabía con anterioridad. El mejoramiento de los estimados poblacionales locales o a nivel de isla requerirá que se estratifique a la isla en forma diferente y que se investiguen los factores que influencian a la probabilidad de detección. Compartir protocolos como este con colaboradores de islas vecinas (por. ej., Cuba, Jamaica, Española), cuyas poblaciones de manatíes comparten material genético, contribuiría a la conservación regional mediante mejores estimaciones poblacionales y monitoreo de la expansión de su ámbito doméstico.

scholarly journals Drivers of Bornean Orangutan Distribution across a Multiple-Use Tropical Landscape

2021 ◽  
Vol 13 (3) ◽  
pp. 458
Author(s):  
Sol Milne ◽  
Julien G. A. Martin ◽  
Glen Reynolds ◽  
Charles S. Vairappan ◽  
Eleanor M. Slade ◽  
...  
Keyword(s):  
Forest Cover ◽  
Food Resource ◽  
Multiple Use ◽  
Natural Forests ◽  
Bornean Orangutan ◽  
Aerial Surveys ◽  
Significant Difference ◽  
The Difference ◽  
Fig Trees ◽  
Abundance And Distribution

Logging and conversion of tropical forests in Southeast Asia have resulted in the expansion of landscapes containing a mosaic of habitats that may vary in their ability to sustain local biodiversity. However, the complexity of these landscapes makes it difficult to assess abundance and distribution of some species using ground-based surveys alone. Here, we deployed a combination of ground-transects and aerial surveys to determine drivers of the critically endangered Bornean Orangutan (Pongo pygmaeus morio) distribution across a large multiple-use landscape in Sabah, Malaysian Borneo. Ground-transects and aerial surveys using drones were conducted for orangutan nests and hemi-epiphytic strangler fig trees (Ficus spp.) (an important food resource) in 48 survey areas across 76 km2, within a study landscape of 261 km2. Orangutan nest count data were fitted to models accounting for variation in land use, above-ground carbon density (ACD, a surrogate for forest quality), strangler fig density, and elevation (between 117 and 675 m). Orangutan nest counts were significantly higher in all land uses possessing natural forest cover, regardless of degradation status, than in monoculture plantations. Within these natural forests, nest counts increased with higher ACD and strangler fig density, but not with elevation. In logged forest (ACD 14–150 Mg ha−1), strangler fig density had a significant, positive relationship with orangutan nest counts, but this relationship disappeared in a forest with higher carbon content (ACD 150–209 Mg ha−1). Based on an area-to-area comparison, orangutan nest counts from ground transects were higher than from counts derived from aerial surveys, but this did not constitute a statistically significant difference. Although the difference in nest counts was not significantly different, this analysis indicates that both methods under-sample the total number of nests present within a given area. Aerial surveys are, therefore, a useful method for assessing the orangutan habitat use over large areas. However, the under-estimation of nest counts by both methods suggests that a small number of ground surveys should be retained in future surveys using this technique, particularly in areas with dense understory vegetation. This study shows that even highly degraded forests may be a suitable orangutan habitat as long as strangler fig trees remain intact after areas of forest are logged. Enrichment planting of strangler figs may, therefore, be a valuable tool for orangutan conservation in these landscapes.

scholarly journals Assessment and novel application of N ‐mixture models for aerial surveys of wildlife

Ecosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Sonja A. Christensen ◽  
Matthew T. Farr ◽  
David M. Williams
Keyword(s):  
Mixture Models ◽  
Aerial Surveys

scholarly journals A reference inventory for aquatic fauna of the Laurentian Great Lakes

2019 ◽  
Vol 45 (6) ◽  
pp. 1036-1046 ◽  
Author(s):  
Anett Trebitz ◽  
Maicie Sykes ◽  
Jonathan Barge
Keyword(s):  
Great Lakes ◽  
Laurentian Great Lakes ◽  
Aquatic Fauna
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