Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys
Generalized additive models (GAMs) with spatially referenced covariates were fitted to data collected during the 1995 and 2001 Icelandic (shipboard and aerial) and Faroese (shipboard only) components of the North Atlantic Sightings Surveys (NASS-95 and NASS-2001). The shipboard surveys extended from...
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Septentrio Academic Publishing
2009
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ftunitroemsoe:oai:ojs.henry.ub.uit.no:article/2711 2023-05-15T16:11:17+02:00 Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys Paxton, Charles GM Burt, M Louise Hedley, Sharon L Víkingsson, Gísli A Gunnlaugsson, Thorvaldur Desportes, Geneviève 2009-09-01 application/pdf https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2711 https://doi.org/10.7557/3.2711 eng eng Septentrio Academic Publishing https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2711/2561 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2711 doi:10.7557/3.2711 Copyright (c) 2009 Charles GM Paxton, M Louise Burt, Sharon L Hedley, Gísli A Víkingsson, Thorvaldur Gunnlaugsson, Geneviève Desportes http://creativecommons.org/licenses/by/3.0/ CC-BY NAMMCO Scientific Publications; Vol 7: North Atlantic Sightings Surveys: Counting whales in the North Atlantic, 1987-2001; 143-160 2309-2491 1560-2206 10.7557/3.7 abundance humpback whales surveys density info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2009 ftunitroemsoe https://doi.org/10.7557/3.2711 https://doi.org/10.7557/3.7 2021-08-16T16:39:00Z Generalized additive models (GAMs) with spatially referenced covariates were fitted to data collected during the 1995 and 2001 Icelandic (shipboard and aerial) and Faroese (shipboard only) components of the North Atlantic Sightings Surveys (NASS-95 and NASS-2001). The shipboard surveys extended from the east coast of Greenland, around Iceland, down to an area along the west coast ofIreland (in 1995) and to the north of the United Kingdom (in 2001). In contrast, the aerial surveys were limited to Icelandic coastal waters only. The aim of the analysis was to predict density, and hence abundance, of humpback whales throughout the survey regions and also to establish if there was any evidence that humpback whale density was related to sea surface temperature or depth.Fitting GAMs to the 1995 data proved problematic and so various subsets of the data were used in an attempt to improve the model fitting. Such difficulties did not occur with the 2001 data. Confidence intervals (CIs) for the abundance estimates were estimated using bootstrap sampling methods.The estimated humpback whale abundance for the region covered by the aerial and shipboard surveys in 1995 was 10,521 (95% CI: 3,716–24,636) using all available data and 7,625 (3,641–22,424) if survey blocks with 0 sightings around the Faroes and south of 60˚ N where no humpback whales were detected were excluded from the analysis. The estimate for the total survey region in 2001 was 14,662 (9,441–29,879). The high upper bounds of the confidence intervals were thought to be caused by a paucity of effort over wide areas of the survey leading to interpolation. Overall, the uncertainty associated with these abundance estimates was approximately equal to, or greater than, that associated with a stratified distance analysis. Given these wide CIs the evidence for a substantial difference in abundance between years was equivocal. However there was evidence to suggest that humpback whales congregated in shallower waters between 6–8˚C. Article in Journal/Newspaper Faroes Greenland Humpback Whale Iceland North Atlantic University of Tromsø: Septentrio Academic Publishing Greenland NAMMCO Scientific Publications 7 143 |
institution |
Open Polar |
collection |
University of Tromsø: Septentrio Academic Publishing |
op_collection_id |
ftunitroemsoe |
language |
English |
topic |
abundance humpback whales surveys density |
spellingShingle |
abundance humpback whales surveys density Paxton, Charles GM Burt, M Louise Hedley, Sharon L Víkingsson, Gísli A Gunnlaugsson, Thorvaldur Desportes, Geneviève Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys |
topic_facet |
abundance humpback whales surveys density |
description |
Generalized additive models (GAMs) with spatially referenced covariates were fitted to data collected during the 1995 and 2001 Icelandic (shipboard and aerial) and Faroese (shipboard only) components of the North Atlantic Sightings Surveys (NASS-95 and NASS-2001). The shipboard surveys extended from the east coast of Greenland, around Iceland, down to an area along the west coast ofIreland (in 1995) and to the north of the United Kingdom (in 2001). In contrast, the aerial surveys were limited to Icelandic coastal waters only. The aim of the analysis was to predict density, and hence abundance, of humpback whales throughout the survey regions and also to establish if there was any evidence that humpback whale density was related to sea surface temperature or depth.Fitting GAMs to the 1995 data proved problematic and so various subsets of the data were used in an attempt to improve the model fitting. Such difficulties did not occur with the 2001 data. Confidence intervals (CIs) for the abundance estimates were estimated using bootstrap sampling methods.The estimated humpback whale abundance for the region covered by the aerial and shipboard surveys in 1995 was 10,521 (95% CI: 3,716–24,636) using all available data and 7,625 (3,641–22,424) if survey blocks with 0 sightings around the Faroes and south of 60˚ N where no humpback whales were detected were excluded from the analysis. The estimate for the total survey region in 2001 was 14,662 (9,441–29,879). The high upper bounds of the confidence intervals were thought to be caused by a paucity of effort over wide areas of the survey leading to interpolation. Overall, the uncertainty associated with these abundance estimates was approximately equal to, or greater than, that associated with a stratified distance analysis. Given these wide CIs the evidence for a substantial difference in abundance between years was equivocal. However there was evidence to suggest that humpback whales congregated in shallower waters between 6–8˚C. |
format |
Article in Journal/Newspaper |
author |
Paxton, Charles GM Burt, M Louise Hedley, Sharon L Víkingsson, Gísli A Gunnlaugsson, Thorvaldur Desportes, Geneviève |
author_facet |
Paxton, Charles GM Burt, M Louise Hedley, Sharon L Víkingsson, Gísli A Gunnlaugsson, Thorvaldur Desportes, Geneviève |
author_sort |
Paxton, Charles GM |
title |
Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys |
title_short |
Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys |
title_full |
Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys |
title_fullStr |
Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys |
title_full_unstemmed |
Density surface fitting to estimate the abundance of humpback whales based on the NASS-95 and NASS- 2001 aerial and shipboard surveys |
title_sort |
density surface fitting to estimate the abundance of humpback whales based on the nass-95 and nass- 2001 aerial and shipboard surveys |
publisher |
Septentrio Academic Publishing |
publishDate |
2009 |
url |
https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2711 https://doi.org/10.7557/3.2711 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Faroes Greenland Humpback Whale Iceland North Atlantic |
genre_facet |
Faroes Greenland Humpback Whale Iceland North Atlantic |
op_source |
NAMMCO Scientific Publications; Vol 7: North Atlantic Sightings Surveys: Counting whales in the North Atlantic, 1987-2001; 143-160 2309-2491 1560-2206 10.7557/3.7 |
op_relation |
https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2711/2561 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/2711 doi:10.7557/3.2711 |
op_rights |
Copyright (c) 2009 Charles GM Paxton, M Louise Burt, Sharon L Hedley, Gísli A Víkingsson, Thorvaldur Gunnlaugsson, Geneviève Desportes http://creativecommons.org/licenses/by/3.0/ |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.7557/3.2711 https://doi.org/10.7557/3.7 |
container_title |
NAMMCO Scientific Publications |
container_volume |
7 |
container_start_page |
143 |
_version_ |
1765996424608088064 |