West Sutherland Elver Survey

West Sutherland Elver Survey 2008
(Godfrey 2007). Mean eel length in NW Scotland between 1996 and 2006 was 221mm,
which is slightly smaller than the East coast of Scotland as would be expected from effects
of density dependent growth and higher recruitment on the west (Godfrey 2007).
MIGRATION
In the highlands, silver eels were recorded migrating to the sea from late September until
late October (Williamson 1976). Migration normally occurs on moonless nights often
associated with spates and stormy weather, and eels may sometimes cross short distances
over land. Silver eels at this stage are only partly mature adults.
There have been very few observation of eel movements from leaving the coast until finding
eggs in Sargasso Sea. Laboratory experiments have shown that Silver eels have heightened
magnetic orientation in autumn in the direction of the Sargasso Sea (van Ginneken et al.
2005b) and energy-balance studies performed in swim-tunnels have demonstrated the
capacity of eels to utilise their fat reserves to swim constantly day and night for at least 6-7
months (though eels have been shown to swim 5533km in 117 days and only burning up
19.7% of body weight). Silver eels are thought to swim at depths below 200m (some have
been caught at 300-700m), where they would catch the cold Canaries current (