Ensis americanus and Mya arenaria in the Wadden Sea

Ensis americanus and Mya arenaria in the Wadden Sea

Fabian Delong, Sam Jantz, Rashed Sheriff, Jan Wildefeld

Coastal and Marine Ecosystem Field Studies, SS 2008

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 sub-tidal and intertidal zones

• Areas of colonization are scarcely populated with native fauna

M. arenaria

• Present in Europe in late Pliocene

• Possibly re-introduced to Europe in the 13th Century by Vikings

• Wide range of habitat and food preferences

• Highest densities found in intertidal and shallow sub-tidal 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

ResultsMean (length vs age)

Mittelwert ±0,95 Konf. Interv. 01 02 03 04 05 06 07

age [years]

40

60

80

100

120

140

160

180

200

leng

th [m

m]

r2 = 0.95

ResultsDead (n = 35)

2 3 4 5 6 7

age [years]

0

2

4

6

8

10

12

Freq

uenc

y

ResultsAlive

1 2 3 4 5 6

age [years]

0

1

2

3

4

5

6

7

Freq

uenc

y

(n = 15)

ImpactsE.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

ImpactsM.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 publicwww.aliens-europe.org

Additional Idea: How to reach the publicwww.aliens-sylt.org ?!

Additional Idea: How to reach the publicwww.aliens-sylt.org ?!

Thank you for your attention