TY - JOUR

T1 - Grey seal Halichoerus grypus recolonisation of the southern Baltic Sea, Danish Straits and Kattegat

AU - Galatius, Anders

AU - Teilmann, Jonas

AU - Daehne, Michael

AU - Ahola, Markus

AU - Westphal, Linda

AU - Kyhn, Line A.

AU - Pawliczka, Iwona

AU - Olsen, Morten Tange

AU - Dietz, Rune

PY - 2020

Y1 - 2020

N2 - The grey seal became locally extinct in the southern Baltic Sea, Danish Straits and Kattegat in the early 1900s after prolonged culling campaigns. Here, we combine national monitoring and anecdotal data from Denmark, Sweden, Germany and Poland to report on the grey seal's recolonisation of those areas and the initial reestablishment of breeding colonies. Grey seal occurrence has steadily increased since year 2003 as evidenced by the coordinated Baltic Sea moult censuses. At the first census in 2003, there were 146 grey seals along the southern Baltic coasts of Sweden and Denmark, ca 1% of the total Baltic Sea population count. Since 2015, this has increased to 2000-2600 grey seals, or ca 7% of the total population count. Since the local extinction, there have been sporadic breeding events in the 1940s on sea ice around Bornholm and in the 1980s and 1990s on haul-outs in Kattegat. In 2003, the first two pups in the southern Baltic Sea were recorded at Rodsand, Denmark. This is to date the only site in the southern Baltic Sea with regular annual pupping since the recolonisation. Since 2000, there have also been sporadic breeding events in Danish Kattegat, southern Sweden, Poland and Germany. At Rodsand, there have been at least 3-10 pups recorded every year since initiation of monitoring in 2011, with an increasing tendency until 2017 with 10 pups counted, which subsequently decreased to 5-6 pups annually in 2018-2020. Compared to recolonising events in the Atlantic, the numbers of pups are low. This may be caused by differences in population dynamics, recolonisation distances, habitat and mortality and effects of rehabilitation programmes. It is likely that the breeding distribution will spread throughout the southern Baltic, Danish Straits and Kattegat if appropriate protection measures of seals and haul-outs are installed.

AB - The grey seal became locally extinct in the southern Baltic Sea, Danish Straits and Kattegat in the early 1900s after prolonged culling campaigns. Here, we combine national monitoring and anecdotal data from Denmark, Sweden, Germany and Poland to report on the grey seal's recolonisation of those areas and the initial reestablishment of breeding colonies. Grey seal occurrence has steadily increased since year 2003 as evidenced by the coordinated Baltic Sea moult censuses. At the first census in 2003, there were 146 grey seals along the southern Baltic coasts of Sweden and Denmark, ca 1% of the total Baltic Sea population count. Since 2015, this has increased to 2000-2600 grey seals, or ca 7% of the total population count. Since the local extinction, there have been sporadic breeding events in the 1940s on sea ice around Bornholm and in the 1980s and 1990s on haul-outs in Kattegat. In 2003, the first two pups in the southern Baltic Sea were recorded at Rodsand, Denmark. This is to date the only site in the southern Baltic Sea with regular annual pupping since the recolonisation. Since 2000, there have also been sporadic breeding events in Danish Kattegat, southern Sweden, Poland and Germany. At Rodsand, there have been at least 3-10 pups recorded every year since initiation of monitoring in 2011, with an increasing tendency until 2017 with 10 pups counted, which subsequently decreased to 5-6 pups annually in 2018-2020. Compared to recolonising events in the Atlantic, the numbers of pups are low. This may be caused by differences in population dynamics, recolonisation distances, habitat and mortality and effects of rehabilitation programmes. It is likely that the breeding distribution will spread throughout the southern Baltic, Danish Straits and Kattegat if appropriate protection measures of seals and haul-outs are installed.

KW - abundance

KW - distribution

KW - management

KW - Pinnipedia

KW - population recovery

KW - survey data

KW - SITE FIDELITY

KW - MOVEMENT

KW - INCREASE

KW - HISPIDA

U2 - 10.2981/wlb.00711

DO - 10.2981/wlb.00711

M3 - Journal article

VL - 2020

JO - Wildlife Biology

JF - Wildlife Biology

SN - 0909-6396

IS - 4

M1 - 00711

ER -