Stiftung Tierärztliche Hochschule Hannover (TiHo)

Aerial surveys for Antarctic minke whales (Balaenoptera bonaerensis) reveal sea ice dependent distribution patterns

ORCID
0000-0002-5028-2419
Affiliation
Institute for Terrestrial and Aquatic Wildlife Research University of Veterinary Medicine Hannover, Foundation Buesum Germany.
Herr, Helena;
ORCID
0000-0002-9664-354X
Affiliation
CSIRO Mathematical and Information Sciences Hobart Tasmania Australia.
Kelly, Natalie;
ORCID
0000-0002-3495-5927
Affiliation
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Bremerhaven Germany.
Dorschel, Boris;
ORCID
0000-0002-9110-001X
Affiliation
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Bremerhaven Germany.
Huntemann, Marcus;
Affiliation
von Thünen Institute Institute of Sea Fisheries Bremerhaven Germany.
Kock, Karl-Hermann;
ORCID
0000-0003-1282-8334
Affiliation
Institute for Terrestrial and Aquatic Wildlife Research University of Veterinary Medicine Hannover, Foundation Buesum Germany.
Lehnert, Linn Sophia;
ORCID
0000-0002-2556-3948
Affiliation
Institute for Terrestrial and Aquatic Wildlife Research University of Veterinary Medicine Hannover, Foundation Buesum Germany.
Siebert, Ursula;
ORCID
0000-0002-2519-7319
Affiliation
Institute for Terrestrial and Aquatic Wildlife Research University of Veterinary Medicine Hannover, Foundation Buesum Germany.
Viquerat, Sacha;
ORCID
0000-0001-7496-453X
Affiliation
Pew Fellow in Marine Conservation, Oceans Initiative Seattle Washington.
Williams, Rob;
Affiliation
Wageningen Marine Research Wageningen University and Research IJmuiden The Netherlands.
Scheidat, Meike

This study investigates the distribution of Antarctic minke whales (AMW) in relation to sea ice concentration and variations therein. Information on AMW densities in the sea ice-covered parts of the Southern Ocean is required to contextualize abundance estimates obtained from circumpolar shipboard surveys in open waters, suggesting a 30% decline in AMW abundance. Conventional line-transect shipboard surveys for density estimation are impossible in ice-covered regions, therefore we used icebreaker-supported helicopter surveys to obtain information on AMW densities along gradients of 0%-100% of ice concentration. We conducted five helicopter surveys in the Southern Ocean, between 2006 and 2013. Distance sampling data, satellite-derived sea-ice data, and bathymetric parameters were used in generalized additive models (GAMs) to produce predictions on how the density of AMWs varied over space and time, and with environmental covariates. Ice concentration, distance to the ice edge and distance from the shelf break were found to describe the distribution of AMWs. Highest densities were predicted at the ice edge and through to medium ice concentrations. Medium densities were found up to 500 km into the ice edge in all concentrations of ice. Very low numbers of AMWs were found in the ice-free waters of the West Antarctic Peninsula (WAP). A consistent relationship between AMW distribution and sea ice concentration weakens the support for the hypothesis that varying numbers of AMWs in ice-covered waters were responsible for observed changes in estimated abundance. The potential decline in AMW abundance stresses the need for conservation measures and further studies into the AMW population status. Very low numbers of AMWs recorded in the ice-free waters along the WAP support the hypothesis that this species is strongly dependent on sea ice and that forecasted sea ice changes have the potential of heavily impacting AMWs.

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