How many seals were there? The global shelf loss during the Last Glacial Maximum and its effect on the size and distribution of grey seal populations

• Published in: PLoS ONE
• Main Authors: Boehme, Lars, Thompson, David, Fedak, Mike, Bowen, Don, Hammill, Mike, Stenson, Gary
• Other Authors: University of St Andrews. School of Biology, University of St Andrews. Scottish Oceans Institute, University of St Andrews. Marine Alliance for Science & Technology Scotland, University of St Andrews. Sea Mammal Research Unit
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: QH301 Biology; SDG 14 - Life Below Water; QH301; North Atlantic; Sea ice
• Online Access: https://hdl.handle.net/10023/3315; https://doi.org/10.1371/journal.pone.0053000; http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0053000

The tagging studies were funded by the Natural Environment Research Council, UK; the Atlantic seal research program, Department of Fisheries and Oceans, Canada and NSERCD Discovery grants, Canada. This work also received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Predicting how marine mammal populations act to habitat changes will be essential for developing conservation management strategies by marine mammal ecologists in the 21st century. Responses to previous environmental change may be informative in the development of predictive models. Here we describe the likely effects of the last ice age on grey seal population size and distribution. We use satellite telemetry data to define grey seal foraging habitat in terms of the temperature and depth ranges exploited by the contemporary populations. We estimate the available extent of such habitat in the North Atlantic at present and at the last glacial maximum (LGM); taking account of glacial and seasonal sea-ice coverage, estimated reductions of sea-level (123m) and seawater temperature hind-casts from GLAMAP-2000. Most of the extensive continental shelf waters (North Sea, Baltic Sea and Scotian Shelf), currently supporting >95% of grey seals, were unavailable at the LGM. A combination of lower sea-level and extensive ice-sheets, massively increased seasonal sea-ice coverage and southerly extent of cold water would have pushed grey seals into areas with no significant shelf waters. The habitat during the LGM might have been as small as 4%, when compared to today’s extent and grey seal populations may have fallen to similarly. An alternative scenario involving a major change to a pelagic/bathy-pelagic foraging niche cannot be ...