It was heartening to read some good news about our eels recently.

They are an important indicator of the environmental health of freshwater habitats.

The European Eel (Anguilla anguilla) is listed as ‘critically endangered’ in the UK and across Europe. Numbers have declined by an estimated 95 per cent since the 1980s.

Last year scientists announced that they had tracked adult European Eels to their spawning ground, the Sargasso Sea near Bermuda, for the first time.

The Eels’ journey is up to 10,000 km long and is considered one of the most impressive feats of animal migration.

After spawning, the eel larvae are carried to UK and European waters on currents of the North Atlantic Drift.

They enter our river systems as tiny ‘glass eels’ or elvers. They live here for up to 20 years before reaching maturity, and then make their final journey back out to the Sargasso Sea to spawn.

One of the main causes of their decline in numbers is the disruption to their migratory pathways by man-made structures along our rivers – weirs, locks, sluices and pumping stations.

Here in the catchment of the River Great Ouse the Environment Agency have built over 35 eel and elver passes to allow the in-coming elvers to disperse into the wider river system and grow, and then to let the mature eels return to the sea to complete their life-cycle.

The eel passes contain brush-like structures where the bristles help the tiny elvers to swim up against the flow. However, new designs are also being trialled with pebbles and stones.

Another experiment is in the use of a ‘spat rope’ at small weirs. When positioned at the edge of a weir, away from the main flow of water, the eels can successfully climb this soft, fibrous rope and continue their journey up-stream.

The Environment Agency try to count the number of eels entering the Great Ouse catchment - a slippery job and there must always be at least one, or maybe many more elvers, that get away.

But at the last count, between March and October 2022, 74,452 eels travelled through the Brownshill staunch eel pass and monitoring station.

This is the third highest number recorded at the station since it began recording in 2008, when just 658 eels passed through. We are very hopeful for the 2023 count!