Page 115 - Sjæklen2009

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Summary
As secretary for the contingency plan for strandings of
marine mammals in Denmark, the Fisheries and Maritime
Museum receives several reports of stranded marine mam-
mals every year. The contingency plan is run jointly by the
Fisheries and Maritime Museum, the Danish Forest and Na-
ture Agency and the Natural History Museum of Denmark,
Zoological Museum in Copenhagen. This article is based on
the work that relates to this contingency plan, and it gives a
brief overview of the different species of marine mammals
that were handled in 2008.
The prime objective of the contingency plan is, as far as
possible, to record all stranded marine mammals along the
Danish coastline and to ensure quick and humane euthanis-
ing of sick and suffering marine mammals. Stranded marine
mammals are also collected by the two museums to ensure
that important information is registered. Tissue samples and
skeletal remains from seals and whales are stored under op-
timal conditions.
In 2008 a total of 309 common seals and 12 grey seals
were registered. Compared to the numbers from 2007 (312
common seals and 29 grey seals), considerately fewer grey
seals were registered in 2008, whereas the number of regis-
tered common seals was constant. On average 133 seals were
registered each year between 2003 and 2006. After a marked
increase in 2007, the number of registrations stayed at this
high level throughout 2008. In 2007 the marked increase
could be explained by an unidentified pathogen among the
common seals at the island of Anholt in the Kattegat Sea –
this was not the case in 2008. Instead the high number of
registrations in 2008 could be explained by a growing seal
population – provided that the percentage of individuals in
the population that succumb to disease is constant.
The majority of the registered seals in 2008 were young
individuals – probably yearlings. In the Wadden Sea the
mortality among yearlings is generally about 30%.
Post mortem examinations of the seals either found dead
or euthanised showed heavy infection with parasites, pri-
marily lungworms. More than half of the seals were young
animals with severe pneumonia due to lungworms. In Ger-
many and the Netherlands this is known to be a widespread
infection and cause of death among yearlings in autumn.
Three of the registered common seals carried tags from
seal rehabilitation centres. Two of them had been tagged at
the Seehundstation Friedrichskoog in Germany, while the
third carried a tag from the Seal Rehabilitation and Research
Centre Pieterburen in the Netherlands.
For the last five years (2003-2007), an average of 124 ce-
taceans has been registered each year in Denmark. In 2008
almost twice as many (235 individuals) were registered; 224
of the registered cetaceans were harbour porpoises. The rea-
son for such a marked increase in the number of harbour
porpoises remains unknown. In 2005 the SCANS-II survey
estimated that the density of harbour porpoises in Danish
waters had decreased since 1994, when a similar estimate
was made.
220 of the registered harbour porpoises were found dead.
Three were found suffering and subsequently euthanised,
and one incidentally caught individual was set free.
Apart from the harbour porpoise, six white-beaked dol-
phins, two white-sided dolphins, one striped dolphin and
two minke whales were registered in 2008. The striped
dolphin is very rare in Danish waters – a striped dolphin
has only previously been reported stranded on the Danish
coastline once.
Sælunge på Langli Sand.