Vergelijking afname vogels in Waddenzee met toename
kokkelvisserij
Naar aanleiding van de recente ineenstorting van het aantal Kanoetstrandlopers
in de Waddenzee en de Eidereendensterfte heeft Wilde Kokkels een vergelijking
gemaakt tussen de hoeveelheid gevangen kokkels en de hoeveelheid schelpetende
vogels in de Waddenzee. De resultaten spreken voor zich.
Increasing shellfish landings….
Mechanical
shellfish-dredging
is a new activity in the Wadden Sea. Cockles were harvest with
hand-gear since a long time but in the late 1970s/early 1980s increasingly
powerful ships with increasingly powerful (suction-)dredges were used.
Despite declining cockle-stocks (not shown), the industry so far has
been able to maintain the harvest rates of the 1980s due to their increased
power and mobility.
….declining populations of birds
depending on shellfish
The
birds have not been so lucky… In the 1970s oystercatchers
started breeding in the heavily fertilised meadows of The Netherlands
and the numbers wintering in the Dutch Wadden Sea increased from 150,000
to 220,000 birds. With the advent of large-scale mechanical cockle dredging,
since the late 1980s numbers have been in decline, with the wintering
population now being even lower than before the discovery of the Dutch
meadows!
About
120,000 Eider Ducks wintered in the Wadden Sea area since at
least the early 1970s. After an initial decrease in the late 1980s they
have been in steep decline in the Wadden Sea since the mid 1990s. Large
numbers have died of starvation and even more birds have tried their
luck along
the North Sea coast.
Knots
are the smallest shellfish-eating specialist, and roam widely between
estuaries in Western Europe. They would be least expected to be negatively
affected by decreasing shellfish stocks since there will be many alternative
sites that they can find. Nevertheless, despite intense counting and
complete coverage, the Knot numbers counted this past winter are the
lowest ever. Never before has their been a steep decline over four successive
winters.
Data made available by SOVON
Bird Research, and from Camphuysen et al 2002
