17
February 2009 - Cadmium, mercury and selenium
levels in the tissues from walrus were similar
to those found in seal species (ringed seal,
harp seal and hooded seal) in the previous
study.
If organochlorine levels
in walrus and hooded seal are compared to
levels found earlier in ringed and harp
seal, no systematic picture is apparent.
In some cases levels in walrus and hooded
seal generally are higher than in the other
seal species (PCBs, DDTs, chlordanes, dieldrin),
whereas in other cases they are lower (toxaphene,
coplanar PCBs).
In the previous study
unexpected high levels of toxaphene were
found in skin compared to blubber of minke
whale sampled in 1998 and analyzed in 2000.
Therefore more samples of minke whale blubber
and skin (also collected in 1998) were analyzed
in 2005. In this set of samples the highest
toxaphene concentrations were found in blubber.
In most cases organochlorine levels in minke
whale skin and blubber analyzed in 2005
were similar to levels found in samples
analyzed in 2000, and although there are
differences, these most likely may be explained
by individual variation (not the same individuals
analyzed in both rounds).
Levels of brominated
diphenyl ethers (PBDEs) in walrus and hooded
seal blubber were at the same level as found
earlier in ringed seal blubber from West
Greenland, but lower than in harp seal blubber.
The highest PBDE concentrations were found
in minke whale blubber.
+ More
Attempt to reduce the
number of cormorants in Ringkøbing
and Nissum Fjords
26 February 2009 - A
national management plan for cormorants
was adopted in Denmark in 2002. The overriding
goal was to ensure the protection and survival
of cormorants at the same time as ensuring
that their number and extent did not give
rise to unacceptable impact for fish populations
and fisheries in Danish waters. The management
plan provided the opportunity to test whether
egg oiling in colonies and shooting of cormorants
in the hunting season could be used as tools
to reduce the number of cormorants within
a limited area. From 2002 to 2008, Ringkøbing
Fjord and Nissum Fjord came to be used as
experimental areas for attempts to reduce
cormorant numbers. This report presents
and evaluates the results from these areas.
The most important conclusions
from the project are:
• The trend in the number
of breeding cormorants in both fjords was
affected by the management measures undertaken
in the colonies, especially egg oiling.
• Oiling is an effective
method to reduce cormorants’ production
of young and thereby a) their requirement
for food and b) breeding numbers in the
longer term. The development in breeding
numbers over the years is also affected,
however, by exchange of individuals between
colonies, which can vary according to e.g.
feeding conditions in the local area and
living conditions in other breeding areas.
• The number of cormorants
present in Ringkøbing and Nissum
Fjords in late summer and autumn did not
decline measurably over the years despite
egg oiling and shooting. Among the reasons
for this was that migrating cormorants came
from a large number of colonies located
over an extensive area and that shooting
did not affect the development of these
individual colonies, nor therefore the number
of cormorants that came annually on migration.
• In Nissum Fjord a
considerable reduction in the number of
cormorants that kept to the fjord in autumn
was achieved by scaring the cormorants away
by means of shooting. For this effect to
be realised, the shooting had to be intensive
and take place close to the sites where
the cormorants roosted during the day and
night, which was only possible in Nissum
Fjord.
+ More
Scale and effects of
intervention measures in Danish cormorant
colonies in Denmark 1994–2008
18 February 2009 - In
Denmark the breeding population of cormorants
grew from a few hundred in the beginning
of the 1970s to around 40,000 pairs in mid-11000s.
As a result the number of conflicts between
cormorants and fisheries in Denmark increased.
In order to avoid further growth in the
cormorant population and to relieve some
of the conflict, the Danish Forest and Nature
Agency introduced a new management practice
in 1994. This aimed to limit the development
of new cormorant colonies in Denmark. In
2002 a new cormorant management plan came
into being, and under this plan the attempts
to limit creation of new colonies was taken
a step further, and as a new measure egg
oiling, in various of the older colonies
where cormorants nested on the ground, was
initiated. This egg oiling, which hinders
eggs hatching while the parents continue
to incubate, was designed to limit the production
of young cormorants in certain areas and,
in the longer term, lead to a reduction
in breeding numbers.
In 1994–2000 and 2001–2008
the Danish Forest and Nature Agency carried
out interventions at an average of nine
and 16 colonies a year, respectively. The
highest number was 19 colonies, and this
corresponded to a third of all cormorant
colonies. In the majority of cases action
was directed at newly established colonies
or in colonies from which the cormorants
had not disappeared despite previous years’
interventions. In 2002–2008 the measures
were to a greater degree carried out in
larger colonies that had existed for a greater
number of years.
The total number of
nests to which the intervention measures
were applied with the result that the nests
or their contents were lost rose from a
total of 7,500 nests in 1994–2001 to a total
of 39,700 nests in 2002–2008. The highest
number of nests subject to regulation by
the Danish Forest and Nature Agency was
in a single year approx. 7,200 nests in
2008, equivalent to a fifth of all cormorant
nests in Denmark.
The conclusions of the
report can be summarised in the following
points:
• By carrying out measures
to scare the birds in the first year they
attempted to establish a new colony, the
probability of the cormorants returning
in subsequent years could be reduced. Shooting
(including the killing of individual birds
in or near the colony) was the most effective
method of avoiding the cormorants returning
the following year.
• In connection with
the cormorants’ attempts to create new colonies
on the ground, it was most often egg oiling
that was selected as the method of intervention.
This method led rarely to the cormorants’
leaving the site the subsequent year, but
in the majority of cases prevented newly
established colonies on the ground from
becoming large. In many cases, shooting
in or near colonies established on the ground
would have resulted in other colony breeding
bird species having been disturbed.
• The measures applied
in new colonies reduced the general ‘risk’
of colonies with growth potential becoming
medium-sized or large.
• Comprehensive oiling
over several years in some of the colonies
on the ground, with several hundred nests,
led to a marked fall in production of young
cormorants. However, it was revealed to
be difficult to predict the effect of the
oiling on developments in the number of
nests, especially due to a high degree of
unpredictability in exchange of individuals
among colonies .
• It is assessed that
the intervention measures which prevented
growth in several new colonies and led to
low production of young in individual large
colonies affected the size of the total
breeding population as well as that of individual
colonies. The intervention measures applied
are assessed to have contributed to the
decline in the total Danish breeding population
that occurred in 2007 and 2008.
Contact: Senior Researcher,
Thomas Bregnballe, tel. 8920 1517, tb@dmu.dk
Forvaltende indgreb
i danske skarvkolonier i Danmark 1994-2008.
– Omfang og effekter af oliering af æg,
bortskræmning og beskydning. Bregnballe,
T. & Eskildsen, J. 2009. Danmarks Miljøundersøgelser,
Aarhus Universitet. 46 s. – Arbejdsrapport
fra DMU nr. 249. Summary (in Danish) | The
full report (in Danish) in pdf format (4.757
kB)
