On the availability bias in narwhal abundance estimates
Abundance estimation of narwhals is usually done with either visual or photographic aerial surveys. The basic estimation for both methods is detection of whales at the surface, and to obtain fully corrected abundance estimates, the at-surface detections need to be corrected for the proportion of wha...
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ftunitroemsoe:oai:ojs.henry.ub.uit.no:article/6518 2023-10-09T21:52:04+02:00 On the availability bias in narwhal abundance estimates Heide-Jørgensen, Mads Peter Lage, Jochim 2022-12-21 application/pdf image/jpeg https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518 https://doi.org/10.7557/3.6518 eng eng Septentrio Academic Publishing https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6936 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6937 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6938 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6939 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6940 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6941 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6942 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6943 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6944 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6945 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518 doi:10.7557/3.6518 Copyright (c) 2022 Mads Peter Heide-Jørgensen, Jochim Lage https://creativecommons.org/licenses/by/4.0 NAMMCO Scientific Publications; Vol. 12 (2022): Marine Mammals in the North Atlantic 2309-2491 1560-2206 10.7557/3.12 Narwhal aerial surveys Greenland diving behavior surface time zero offset correction info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 2022 ftunitroemsoe https://doi.org/10.7557/3.651810.7557/3.12 2023-09-20T23:07:55Z Abundance estimation of narwhals is usually done with either visual or photographic aerial surveys. The basic estimation for both methods is detection of whales at the surface, and to obtain fully corrected abundance estimates, the at-surface detections need to be corrected for the proportion of whales that, at any given time, is available to be detected at the surface. The surfacing time or ‘availability correction factor’ is obtained from whales instrumented with dive recorders, that either relay concatenated information on the proportion of time spent at different depth intervals to satellites, or from recovered instruments that collect complete dive profiles, measured at high frequency. Concatenated data binned in depth histograms from Satellite-Linked-Time-Depth-Recorders (SLTDR) falls in two categories, where those that correct the zero depth values with information from the saltwater switch provide larger and apparently more accurate surfacing times, than those collected from instruments that does not correct the zero depth readings. The erroneous detection of near-surface pressure values is likely due to slow response of pressure transducers made from temperature sensitive materials. The high frequency sampling from AcousondeTM recorders documents erroneous surface detections, and adjustments of the dive profiles are needed to obtain realistic near-surface values. Any reconstruction of dive profiles and near-surface values apparently involves some level of corrections and it is recommended, for development of availability correction factors for aerial surveys, that data from zero-adjusted SLTDRs or TDR instruments are used. The mean estimate of surface time from 7 SLTDRs was 29% (CV=0.05). One SLTDR, with steel pressure transducer and zero-adjustments, that was retrieved from the whale, provided a particular long-record (83 days) of reliable high-resolution data. The surface time for this sample was 31%, when calculated as the sum of all depth readings at or above 2 m. The mean of 144 hourly depth ... Article in Journal/Newspaper Greenland narwhal* University of Tromsø: Septentrio Academic Publishing Greenland |
institution |
Open Polar |
collection |
University of Tromsø: Septentrio Academic Publishing |
op_collection_id |
ftunitroemsoe |
language |
English |
topic |
Narwhal aerial surveys Greenland diving behavior surface time zero offset correction |
spellingShingle |
Narwhal aerial surveys Greenland diving behavior surface time zero offset correction Heide-Jørgensen, Mads Peter Lage, Jochim On the availability bias in narwhal abundance estimates |
topic_facet |
Narwhal aerial surveys Greenland diving behavior surface time zero offset correction |
description |
Abundance estimation of narwhals is usually done with either visual or photographic aerial surveys. The basic estimation for both methods is detection of whales at the surface, and to obtain fully corrected abundance estimates, the at-surface detections need to be corrected for the proportion of whales that, at any given time, is available to be detected at the surface. The surfacing time or ‘availability correction factor’ is obtained from whales instrumented with dive recorders, that either relay concatenated information on the proportion of time spent at different depth intervals to satellites, or from recovered instruments that collect complete dive profiles, measured at high frequency. Concatenated data binned in depth histograms from Satellite-Linked-Time-Depth-Recorders (SLTDR) falls in two categories, where those that correct the zero depth values with information from the saltwater switch provide larger and apparently more accurate surfacing times, than those collected from instruments that does not correct the zero depth readings. The erroneous detection of near-surface pressure values is likely due to slow response of pressure transducers made from temperature sensitive materials. The high frequency sampling from AcousondeTM recorders documents erroneous surface detections, and adjustments of the dive profiles are needed to obtain realistic near-surface values. Any reconstruction of dive profiles and near-surface values apparently involves some level of corrections and it is recommended, for development of availability correction factors for aerial surveys, that data from zero-adjusted SLTDRs or TDR instruments are used. The mean estimate of surface time from 7 SLTDRs was 29% (CV=0.05). One SLTDR, with steel pressure transducer and zero-adjustments, that was retrieved from the whale, provided a particular long-record (83 days) of reliable high-resolution data. The surface time for this sample was 31%, when calculated as the sum of all depth readings at or above 2 m. The mean of 144 hourly depth ... |
format |
Article in Journal/Newspaper |
author |
Heide-Jørgensen, Mads Peter Lage, Jochim |
author_facet |
Heide-Jørgensen, Mads Peter Lage, Jochim |
author_sort |
Heide-Jørgensen, Mads Peter |
title |
On the availability bias in narwhal abundance estimates |
title_short |
On the availability bias in narwhal abundance estimates |
title_full |
On the availability bias in narwhal abundance estimates |
title_fullStr |
On the availability bias in narwhal abundance estimates |
title_full_unstemmed |
On the availability bias in narwhal abundance estimates |
title_sort |
on the availability bias in narwhal abundance estimates |
publisher |
Septentrio Academic Publishing |
publishDate |
2022 |
url |
https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518 https://doi.org/10.7557/3.6518 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland narwhal* |
genre_facet |
Greenland narwhal* |
op_source |
NAMMCO Scientific Publications; Vol. 12 (2022): Marine Mammals in the North Atlantic 2309-2491 1560-2206 10.7557/3.12 |
op_relation |
https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6936 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6937 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6938 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6939 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6940 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6941 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6942 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6943 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6944 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518/6945 https://septentrio.uit.no/index.php/NAMMCOSP/article/view/6518 doi:10.7557/3.6518 |
op_rights |
Copyright (c) 2022 Mads Peter Heide-Jørgensen, Jochim Lage https://creativecommons.org/licenses/by/4.0 |
op_doi |
https://doi.org/10.7557/3.651810.7557/3.12 |
_version_ |
1779315196657926144 |