Under-shelf ice foraging of Weddell seals

The Drescher Inlet is a 25km long crack in the Riiser-Larsen Ice Shelf, eastern Weddell Sea, and is characterized by a stable fast ice layer. The fast ice represents an attractive habitat for Weddell seals, aggregating along the tidal cracks of the inlet in numbers of ca. 200 – 300 individuals. Mult...

Full description

Bibliographic Details
Main Authors: Nachtsheim, Dominik, Held, Christoph, Owsianowski, Nils, Plötz, Joachim, Steinmetz, Richard, Naito, Yasuhiko, Bornemann, Horst
Format: Conference Object
Language:unknown
Published: 2017
Subjects:
Online Access:https://epic.awi.de/id/eprint/45200/
https://hdl.handle.net/10013/epic.51378
id ftawi:oai:epic.awi.de:45200
record_format openpolar
spelling ftawi:oai:epic.awi.de:45200 2023-05-15T16:41:53+02:00 Under-shelf ice foraging of Weddell seals Nachtsheim, Dominik Held, Christoph Owsianowski, Nils Plötz, Joachim Steinmetz, Richard Naito, Yasuhiko Bornemann, Horst 2017-07-12 https://epic.awi.de/id/eprint/45200/ https://hdl.handle.net/10013/epic.51378 unknown Nachtsheim, D. , Held, C. orcid:0000-0001-8854-3234 , Owsianowski, N. orcid:0000-0003-4104-4926 , Plötz, J. , Steinmetz, R. , Naito, Y. and Bornemann, H. (2017) Under-shelf ice foraging of Weddell seals , XIIth Biology Symposium of the Scientific Committee of Antarctic Research (SCAR) "Scale Matters", Leuven, Belgium, 10 July 2017 - 14 July 2017 . hdl:10013/epic.51378 EPIC3XIIth Biology Symposium of the Scientific Committee of Antarctic Research (SCAR) "Scale Matters", Leuven, Belgium, 2017-07-10-2017-07-14 Conference notRev 2017 ftawi 2022-10-02T23:12:36Z The Drescher Inlet is a 25km long crack in the Riiser-Larsen Ice Shelf, eastern Weddell Sea, and is characterized by a stable fast ice layer. The fast ice represents an attractive habitat for Weddell seals, aggregating along the tidal cracks of the inlet in numbers of ca. 200 – 300 individuals. Multiple field campaigns aimed to investigate the seals’ diving behaviour and foraging ecology in relation to their environment. A recent joint seal and ROV project was focussed on the investigation of the cryo-benthic community underneath the floating ice shelf of the Drescher Inlet, which were previously detected by seal-borne cameras, and 3D-multi-channel dive loggers (Watanabe et al. 2006; Liebsch et al. 2007). Images show dense aggregations of isopods that likely represent an attractive food horizon, where seals could benefit from a local hotspot of high biological productivity. This context triggered a retrospective analysis of available high-resolution dive profile data to identify within-dive hunting phases and correlate those to the local physical environment. A total of 34 adult Weddell seals were instrumented with different types of dive loggers (time-depth recorders, digital still image loggers) in the course of six summer field campaigns between 1990 and 2016. Dive profiles were zero-offset corrected to reduce noise in the dataset and subsequently only dives deeper than 20m were regarded as ‘true’ dives, accounting for the thickness of the local fast ice and platelet ice layer. An automated broken stick algorithm (Heerah et al. 2014) was used to separate the dive into different segments. Segments with a high sinuosity were considered to indicate hunting. Segments characterized by a straight dive trajectories (low sinuosity), were assumed to be transit phases with no hunting behaviour. A tri-modal distribution of mean hunting depths suggests that Weddell seals concentrated their foraging activities in three depth strata. A peak in hunting depths below 370m corresponds to the sea floor of the Drescher Inlet, ... Conference Object Ice Shelf Larsen Ice Shelf Riiser Larsen Ice Shelf Riiser-Larsen Ice Shelf Weddell Sea Weddell Seals Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Weddell Sea Weddell Riiser-Larsen ENVELOPE(50.667,50.667,-66.783,-66.783) Larsen Ice Shelf ENVELOPE(-62.500,-62.500,-67.500,-67.500) Riiser-Larsen Ice Shelf ENVELOPE(-20.000,-20.000,-74.417,-74.417)
institution Open Polar
collection Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center)
op_collection_id ftawi
language unknown
description The Drescher Inlet is a 25km long crack in the Riiser-Larsen Ice Shelf, eastern Weddell Sea, and is characterized by a stable fast ice layer. The fast ice represents an attractive habitat for Weddell seals, aggregating along the tidal cracks of the inlet in numbers of ca. 200 – 300 individuals. Multiple field campaigns aimed to investigate the seals’ diving behaviour and foraging ecology in relation to their environment. A recent joint seal and ROV project was focussed on the investigation of the cryo-benthic community underneath the floating ice shelf of the Drescher Inlet, which were previously detected by seal-borne cameras, and 3D-multi-channel dive loggers (Watanabe et al. 2006; Liebsch et al. 2007). Images show dense aggregations of isopods that likely represent an attractive food horizon, where seals could benefit from a local hotspot of high biological productivity. This context triggered a retrospective analysis of available high-resolution dive profile data to identify within-dive hunting phases and correlate those to the local physical environment. A total of 34 adult Weddell seals were instrumented with different types of dive loggers (time-depth recorders, digital still image loggers) in the course of six summer field campaigns between 1990 and 2016. Dive profiles were zero-offset corrected to reduce noise in the dataset and subsequently only dives deeper than 20m were regarded as ‘true’ dives, accounting for the thickness of the local fast ice and platelet ice layer. An automated broken stick algorithm (Heerah et al. 2014) was used to separate the dive into different segments. Segments with a high sinuosity were considered to indicate hunting. Segments characterized by a straight dive trajectories (low sinuosity), were assumed to be transit phases with no hunting behaviour. A tri-modal distribution of mean hunting depths suggests that Weddell seals concentrated their foraging activities in three depth strata. A peak in hunting depths below 370m corresponds to the sea floor of the Drescher Inlet, ...
format Conference Object
author Nachtsheim, Dominik
Held, Christoph
Owsianowski, Nils
Plötz, Joachim
Steinmetz, Richard
Naito, Yasuhiko
Bornemann, Horst
spellingShingle Nachtsheim, Dominik
Held, Christoph
Owsianowski, Nils
Plötz, Joachim
Steinmetz, Richard
Naito, Yasuhiko
Bornemann, Horst
Under-shelf ice foraging of Weddell seals
author_facet Nachtsheim, Dominik
Held, Christoph
Owsianowski, Nils
Plötz, Joachim
Steinmetz, Richard
Naito, Yasuhiko
Bornemann, Horst
author_sort Nachtsheim, Dominik
title Under-shelf ice foraging of Weddell seals
title_short Under-shelf ice foraging of Weddell seals
title_full Under-shelf ice foraging of Weddell seals
title_fullStr Under-shelf ice foraging of Weddell seals
title_full_unstemmed Under-shelf ice foraging of Weddell seals
title_sort under-shelf ice foraging of weddell seals
publishDate 2017
url https://epic.awi.de/id/eprint/45200/
https://hdl.handle.net/10013/epic.51378
long_lat ENVELOPE(50.667,50.667,-66.783,-66.783)
ENVELOPE(-62.500,-62.500,-67.500,-67.500)
ENVELOPE(-20.000,-20.000,-74.417,-74.417)
geographic Weddell Sea
Weddell
Riiser-Larsen
Larsen Ice Shelf
Riiser-Larsen Ice Shelf
geographic_facet Weddell Sea
Weddell
Riiser-Larsen
Larsen Ice Shelf
Riiser-Larsen Ice Shelf
genre Ice Shelf
Larsen Ice Shelf
Riiser Larsen Ice Shelf
Riiser-Larsen Ice Shelf
Weddell Sea
Weddell Seals
genre_facet Ice Shelf
Larsen Ice Shelf
Riiser Larsen Ice Shelf
Riiser-Larsen Ice Shelf
Weddell Sea
Weddell Seals
op_source EPIC3XIIth Biology Symposium of the Scientific Committee of Antarctic Research (SCAR) "Scale Matters", Leuven, Belgium, 2017-07-10-2017-07-14
op_relation Nachtsheim, D. , Held, C. orcid:0000-0001-8854-3234 , Owsianowski, N. orcid:0000-0003-4104-4926 , Plötz, J. , Steinmetz, R. , Naito, Y. and Bornemann, H. (2017) Under-shelf ice foraging of Weddell seals , XIIth Biology Symposium of the Scientific Committee of Antarctic Research (SCAR) "Scale Matters", Leuven, Belgium, 10 July 2017 - 14 July 2017 . hdl:10013/epic.51378
_version_ 1766032360296415232