130925-studie-wildlife-comeback-in-europe

Figure 3.
Map of recent
developments
recorded for the
Harbour seal in
Europe.
Expansion
Persistence
Contraction
S
jB jB d
¿
jB
jB
B Habitat
degradation/
change
S Legal protection
d
Accidental
mortality
À
Population
increase
i New sighting (in
river tributary)
→ Further range
expansion
i
Recent developments
There have been a number of mass mortality events
in European seals in the past [12, 36] , and disease [44] and
high levels of pollution [45] continue to be a problem.
For example, over 900 seals, many of them
juveniles, were left dead on the Schleswig-Holstein
coast in 2010 due to a suspected nematode infestation
[46] . In addition, widespread high concentrations
of organochloride compounds from contaminated
prey have been identified in a number of seal
populations, including the Baltic area and Swedish
coast [47] , the Dutch coast [48] , German Wadden Sea [49]
and Britain [50] . These contaminants are released in
the seal’s body when fat reserves are mobilised and
have been shown to affect reproductive success [10, 47] .
Conflict with fisheries, and associated culling and
by-catch mortality, are also sizeable threats to
the species. In addition, human disturbance is an
issue; it has been shown, for example, that human
presence at haul-out sites has a detrimental effect
on seal behaviour [51] . There are also concerns over
the genetic diversity of the species in Europe due
to bottlenecks and the resulting fragmentation of
populations, with some populations showing low
effective population size, such as in Svalbard [52] .
Recently, an increasing number of seal carcasses
has been found in England (Norfolk), Scotland and
Northern Ireland [53] exhibiting so called corkscrew
lacerations [23, 53] . The resulting single smooth-edged
cut starting at the head and spiralling down the
body (skin and blubber are often detached from the
underlying tissue) [23] is consistent with seals being
drawn through a ducted propeller [23, 53] . In total,
over 65 grey and harbour seals of all age classes
and sexes have been recovered [23] . While this level
of mortality is negligible in large populations, it
may well exacerbate declines in smaller populations
[23] . For example, it is considered a significant
cause of mortality in the Firth of Tay [53] . In addition,
the species may be increasingly driven from sites
through developments in marine renewables such
as costal and off-shore wind farms, as has been
observed at Scroby Sands (UK) [54] .
However, there are also positive developments
for the Harbour seal. In Scotland, the outdated
Conservation of Seals Act 1970 was replaced with
the Marine (Scotland) Act 2010 (Part 6) [27] . This Act
increases protection, including a new offence of
harassment at designated haul-out sites. Although
shooting of seals for the protection of fisheries is
still permitted, it is regulated by licence and there
are specific limits on numbers that may be taken
in each of seven Seal Management Areas around
Scotland [27] . Plans by the Scottish government to
protect coastal sites used by only half the nation’s
seals have been widely criticised [55] , but may
represent an important first step. In Germany,
counts of Harbour seals on the Niedersachsen
coast revealed the largest population size since
records began in 1958, with a total number of over
6,600 individuals [56] . Overall, the number of seals
in the Wadden Sea reached over 21,600 in 2009 [57]
and grew to over 24,100 in 2011 [13] . There are also
records of the species spreading further south,
and into large rivers. One individual was sighted
200 km inland in the Dordogne river in southwest
France [58] .
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