The first migrating eel of the year has been spotted in a north Norfolk riverway after having travelled thousands of miles.

The European eel was photographed in Blakeney Freshes sluice this week by members of the National Trust which arrive in our waterways after drifting across the Atlantic for up to three years.

According to the Trust, the eel eggs are spawned in the Sargasso Sea, more than 5000km away, where they float on the current and hatch into larvae that transform into glass eels along the way.

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When they arrive the eels are small and transparent but will eventually grow to be up to one metre long over their 25 to 30-year lifespan in Norfolk's marshes and dykes. 

As part of their regular checks on the species, the National Trust uses 'eel mops' which are placed at sluice gates to catch the juvenile eels which they measure and count and then release to carry on their journeys further inland.

The slippery sea creatures adapt to freshwater and mature in rivers over several decades until they are ready to migrate back to the Sargasso Sea to reproduce and die, restarting the cycle.

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National Trust ranger, Carl Brooker said: "They really are fascinating creatures and it’s amazing that any make it this far."

From May to June the Trust expects to find around 20 eels a day but since the 1980s there has been a more than 90pc decline in the species due to an increase in ocean pollution among other factors.

The news follows shortly after it was discovered that Swallowtail butterfly numbers have fallen by a quarter since 1976 according to a wildlife charity report.