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8 October 2020 Grey seal Halichoerus grypus recolonisation of the southern Baltic Sea, Danish Straits and Kattegat
Anders Galatius, Jonas Teilmann, Michael Dähne, Markus Ahola, Linda Westphal, Line A. Kyhn, Iwona Pawliczka, Morten Tange Olsen, Rune Dietz
Author Affiliations +
Figure 1.
Map of the North and Baltic Seas with place names mentioned in the manuscript. Dashed lines indicate international borders. The limits of the study area are marked by red lines.

Figure 2.
Map of important grey seal haul-out localities (crosses) in Kattegat and southern Baltic Sea. Column charts show moult abundance of grey seals for haul-out with more than 10 grey seals recorded, or total counts of several haul-outs around the main island in the cases of Rügen and Læsø. First bar represents the average count for the years 2001–2005, second bar 2006–2010, third bar 2011–2015 and fourth bar 2016–2019. Note, that Y-axis values range from 0 to 100 or 0 to 1000, depending on the size of the haul-out. N/A means that data are not available from the period in concern. Red crosses denote haul-outs with breeding activity after 1990, circled crosses denote haul-outs with historic breeding activity.

Figure 3.
Counted seals during the moult aerial censuses of grey seals in the Baltic Sea area. Solid line, square markers (left axis): total number of grey seals counted on haul-outs throughout the Baltic Sea. Solid line, round markers (left axis): total number of grey seals counted on haul-outs in the southern Baltic, Danish Straits and Kattegat (southern Sweden, Denmark, Germany and Poland). Dashed line, crosses (right axis): percentage of total number of seals that were counted on haul-outs in the southern Baltic. In 2018, the coordinated count was not conducted in important areas in Finland, so a total number is not available.

Table 1.
Maximum number of pups counted at each of the localities under the Danish monitoring programme since 2011. Ertholmene was added to the programme in 2012, Bosserne was added in 2017. Localities are given in Fig. 2. An ‘X’ denotes that the locality was not covered in the concerned year. Modelled pupping estimates for Rødsand are given in parentheses.

population recovery
survey data
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