Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Distance sampling surveys for cetaceans in Antarctic waters
Lehnert, L.S. ; Geelhoed, S.C.V. ; Gray, I. ; Lehnert, K. ; Plon, S. ; Schmidt, K. ; Verdaat, J.P. ; Gilles, A. ; Herr, H. ; Siebert, U. - \ 2012
Berichte zur Polar- und Meeresforschung 646 (2012). - ISSN 1618-3193 - p. 51 - 55.
Sighting surveys from a ship and a helicopter in the Weddell Sea in 2006/07 and 2008/09
Kock, K.H. ; Herr, H. ; Scheidat, M. ; Braeger, S. ; Lehnert, K. ; Lehnert, L.S. ; Verdaat, J.P. ; Williams, R. ; Siebert, U. ; Boebel, O. - \ 2010
Agadir : International Whaling Commission
Helicopter and shipboard surveys were conducted for cetaceans in the Weddell Sea from the German research vessel ‘Polarstern’. The first survey in 2006/07 started south of South Africa, went to Neumayer Station in Atka Bay (70°29.6’ S/07°57.6’ W), crossed the Weddell Sea from Neumayer to south of Elephant Island and worked around the South Shetland Islands and east of the Antarctic Peninsula in front of former Larsen A and B glaciers. The second survey covered two transects: the first more westerly one started at 57°09.3’ S/00°39.1’ E and went to Atka Bay (70°29.6’ S/07°57.6’ W) whereas the second (return leg) followed a more easterly course from Atka Bay over Maud Rise to 57°03.1’ S/12° 27.5’ W. No observations could be conducted from 63 to 57°S on the return cruise due to fog (visibility <200 m) and swell. Standard line transect survey protocols were followed while the helicopter and the ship followed track lines that could not be designed (i.e. fully randomized) in advance due to unpredictability of the ice conditions and the need to meet several objectives simultaneously. Helicopter track lines covered a total of 13 124 and, 13 417 km in 2006 and 2008 respectively while the ship survey covered 1 171 and 2 011 km respectively. We were particularly interested in the distribution and abundance of Antarctic minke whales in the pack-ice. Minke whales were primarily seen in the ice. Killer and southern bottlenose whales were also seen in the ice while all baleen whales other than minke whales, and sperm whales were only observed in open water. Humpback whales were the most frequently sighted species on the shipboard survey in 2006/07 and the helicopter survey in 2008/09. Environmental information, including proportion ice coverage, was collected continuously. One striking finding from this summary was a much higher encounter rate for all cetaceans from the ship than from the helicopter. This difference could be explained by observers on the helicopter missing more animals on the track line than those from the ship (i.e. g (0) <1); it could equally be explained if whales, were drawn to leads created while RV ‘Polarstern’ broke the ice. This discrepancy warrants closer attention
The occurence of cetaceans along two transects from 57 S to Atka Bay
Kock, K.H. ; Scheidat, M. ; Boebel, O. ; Braeger, S. ; Herr, H. ; Lehnert, K. ; Lehnert, L.S. ; Verdaat, J.P. ; Williams, R. - \ 2009
Madeira : International Whaling Commission
Seals at sea: modelling seal distribution in the German bight based on aerial survey data
Herr, H. ; Scheidat, M. ; Lehnert, K. ; Siebert, U. - \ 2009
Marine Biology 156 (2009)5. - ISSN 0025-3162 - p. 811 - 820.
phoca-vitulina - harbor seals - satellite telemetry - diving behavior - common seals - moray firth - grey seals - wadden sea - space-use - scotland
The Wadden Sea is an important habitat for harbour seals and grey seals. They regularly haul-out on sandbanks and islands along the coast. Comparably little is known about the time seals spend at sea and how they use the remainder of the North Sea. Yet, human activity in offshore waters is increasing and information on seal distribution in the North Sea is crucial for conservation and management. Aerial line transect surveys were conducted in the German bight from 2002 to 2007 to investigate the distribution and abundance of marine mammals. Distance sampling methodology was combined with density surface modelling for a spatially explicit analysis of seal distribution in the German North Sea. Depth and distance to coast were found to be relevant predictor variables for seal density. Density surface modelling allowed for a depiction of seal distribution in the study area as well as an abundance estimate. This is the first study to use aerial survey data to develop a density surface model (DSM) for a spatially explicit distribution estimate of seals at sea
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