Endangered eels have been seen in the River Tud for the first time in four decades as efforts to introduce them into new habitats are seeing 'encouraging results'.
The Environment Agency has been trying to improve access to freshwater habitats for eels in Norfolk.
Increased numbers have been seen at a Norwich fish pass, as well as sightings further upstream on the River Tud.
It is the first time eels have been seen in that location for more than 40 years.
Jez Wood, a specialist at the Environment Agency, said: 'Last month two small eels were found on a routine fish survey on the Tud, a tributary of the Wensum.
'Two doesn't sound like many but these are the only small eels we've found on this stretch for years, and only the fifth and sixth of this size found in the Wensum catchment since 1973.
'Whilst this does not herald the recovery of the species as a whole, it does show the positive benefit of eel passes at barriers to migration and the monitoring programme at the Environment Agency.'
The global eel population has dropped dramatically over the past 40 years, with numbers down by as much as 95pc.
Barriers to upstream migration reduce access to freshwater habitat in which many eels prefer to live while they mature, before migrating back across the Atlantic to the Sargasso Sea where they spawn and die.
In Norfolk barriers include tidal sluices, weirs and mills. Eel passes are helping the Environment Agency ensure the population can be restored and stabilised.
The status of the European eel is still regarded as 'critical' and the agency is creating passes at several key obstruction locations on the throughout Norfolk rivers, such as New Mills Yard, in Norwich.
Eel numbers are monitored by the Environment Agency at various tidal structures and also in fish monitoring surveys on the rivers. Since the New Mills pass was installed in 2009, the number of eels have ranged from the hundreds to a record 34,000 in 2016.
These are not new eels fresh from the Sargasso, but older eels which have spent time in the Broads for maybe two or three years before attempting to migrate upstream.
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