Transcript Enis americanus and Mya arenaria in the Wadden Sea

Ensis americanus and Mya
arenaria in the Wadden Sea
Coastal and Marine Ecosystem Field Studies, SS 2008
Fabian Delong, Sam Jantz, Rashed Sheriff, Jan Wildefeld
E. americanus
• Introduced to
Europe in the late
1970’s
• Rapidly spread
along the
continental
coastline of the
North Sea
• Occupies the
sediment in the subtidal and intertidal
zones
• Areas of
colonization are
scarcely populated
with native fauna
M. arenaria
• Present in Europe
in late Pliocene
• Possibly reintroduced to
Europe in the 13th
Century by
Vikings
• Wide range of
habitat and food
preferences
• Highest densities
found in intertidal
and shallow subtidal zones
Methods
• Sampled individuals of E. americanus
along a 50 meter transect on the lower
portion of the intertidal zone
• 50 individuals, 35 dead and 15 living
• Measured length and counted growth
ridges
Results
Mean (length v s age)
200
r2 = 0.95
180
160
length [mm]
140
120
100
80
60
40
01
02
03
04
05
age [y ears]
06
07
Mittelwert
±0,95 Konf . Interv .
Results
Dead (n = 35)
12
10
Frequency
8
6
4
2
0
2
3
4
5
age [years]
6
7
Results
Aliv e (n = 15)
7
6
Frequency
5
4
3
2
1
0
1
2
3
4
age [y ears]
5
6
Impacts
E.americanus
• No significant interactions with native species
• Possibly hazardous for bathers. Occurs in fairly
shallow depths
• Can cause damage to trawls and other
commercial fishing equipment
Impacts
M.arenaria
• No information is available on impact since
invasion of North Sea
• No negative impacts on other species is
observed today
• Has been observed to competitively exclude
native species in other regions
Management
M.arenaria
• Has been thoroughly established for several
centuries and seems to be benign. No action
is needed
E.americanus
• Seemingly benign, however population
sizes as well as interactions with native
species should be monitored
Additional Idea: How to reach the public
www.aliens-europe.org
Additional Idea: How to reach the public
www.aliens-sylt.org ?!
Additional Idea: How to reach the public
www.aliens-sylt.org ?!
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