Table 4 Sampling details including number of individuals per sampling location (N), latitude, longitude and sea-surface temperature at river mouth averaged across the 30 days preceding the sampling date

Spain

Valencia

44

39°46′ N

0°24′ W

15 January 2010

15.05

Italy

Tiber

39

41°73′ N

12°23′ E

30 December 2007

14.17

South France

Canet

40

42°70′ N

3°15′ E

23 January 2008

13.24

West France

Gironde

40

44°86′ N

0°42′ W

16 April 2008

11.26

Ireland

Burrishoole

39

53°90′ N

9°58′ W

14 March 2005

9.57

Northern Ireland

Lough Erne

39

54°46′ N

7°77′ W

1 July 2008

13.85

Sweden

Ringhals

40

57°21′ N

12°27′ E

15 March 2008

4.19

Iceland

40

May – June 2001

8.45

Stokkseyri

10

63°81′ N

21°04′ W

Vifilsstadvatn

10

64°07′ N

21°87′ W

Seljar

10

64°56′ N

22°31′ W

Vogslækur

10

64°69′ N

22°33′ W