Large numbers of eels returning to Fens and a special pass created to allow them to migrate into the Middle Level

23:01 12 July 2014

Cliff Carson, Environmental Officer for the Middle Level Commissioners monitoring elver numbers at the St Germans Pumping Station elver pass.

Cliff Carson, Environmental Officer for the Middle Level Commissioners monitoring elver numbers at the St Germans Pumping Station elver pass.

Archant

An exceptionally early arrival of large numbers of elvers and eels has been recorded at the new Wiggenhall St Germans Pumping Station elver pass near Kings Lynn.

The size of eels that climb the elver pass range from tiny elvers to much larger young adult eels.The size of eels that climb the elver pass range from tiny elvers to much larger young adult eels.

After decades of poor numbers of young eels returning from their breeding grounds in the Sargasso Sea, a significant improvement has been recorded in 2014 at many sites around the UK.

An elver pass has been installed to allow the young eels to migrate into the waterways of the Middle Level catchment.

Cliff Carson, Environmental Officer for the Middle Level BAP Partnership said: “It is great to see a boom year for elvers after so very many years when their numbers were less than five per cent of the former totals returning to the UK.

“We hope this improved trend will continue. The St Germans Pumping Station elver pass will give excellent access for eels and elvers into the Middle Level rivers and drains that will benefit eel population recovery in the future’

The elver pass during construction. The green bristle tufts in the trough enable the elvers to climb its 35 meter length. 
                                Photo Cliff Carson  ref. IMG_9281The elver pass during construction. The green bristle tufts in the trough enable the elvers to climb its 35 meter length. Photo Cliff Carson ref. IMG_9281

The catchment covers 70,000 hectares of the Cambridgeshire and West Norfolk fens between the Nene Washes near Peterborough and the Ouse Washes from Earith to Downham Market.

At the beginning of April the first elvers of the year were seen making their way up the 35 meter long pass from the tidal River Ouse. The elver pass is an angled trough with bristle boards inside it that help the eels to climb up it. They are attracted to it by the fresh water that is trickled down the trough from the upstream side.

Glass eels are the early stage of elvers (young eels) and are nearly transparent. They are thinner than a shoe lace and less than three inches (75mm) long. During the first three weeks of April nearly 50,000 elvers made their way through the pass.

“This is an exceptional quantity for so early in the elver migration period which lasts from April to October,” said Mr Carson.

The elver pass on the tidal side of the pumping station. The elvers climb eight meters in height and 35 meters in length.                                                Photo Cliff Carson ref. IMG_9253The elver pass on the tidal side of the pumping station. The elvers climb eight meters in height and 35 meters in length. Photo Cliff Carson ref. IMG_9253

“There is a chamber at the top of the elver pass where they can rest and be counted. It is difficult to count the small elvers in quantity but they can be weighed and their numbers calculated from the weight.

“As the season progresses the glass eels become darker and are referred to as elvers.

Later, larger young eels also climb the elver pass. They too are looking for fresh water in the Middle Level catchment to feed in.”

He said: “They will spend the next 10 to 15 years growing and putting on fat that will sustain them on their long journey back to their breeding grounds in the Sargasso Sea.”

The new St Germans Pumping Station near Wiggenhall St Germans, Kings Lynn. It is one of the largest pumping stations in Europe.          Photo Cliff Carson   ref. IMG_2394The new St Germans Pumping Station near Wiggenhall St Germans, Kings Lynn. It is one of the largest pumping stations in Europe. Photo Cliff Carson ref. IMG_2394

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