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Last updated: Sat 5 Oct 2013

Nunney Castle weir finished

English Heritage has finished work to replace a weir in the Nunney Brook, essential for supplying the moat of Nunney Castle.

Nunney Castle weir

The weir is located opposite The George at Nunney

The weir is located next to the car park opposite The George at Nunney on Church Street. The existing weir is constructed of large boulders that have gradually been washed away.

The Nunney Castle weir is essential to feed water into the moat surrounding the castle. Due to the state of the old weir, the moat had become largely stagnant. Once one of the deepest moats in the country, the water level had dropped and the moat was filled with algae.

A pipe runs from the weir in the Nunney Brook into the moat. However, it was silted up, overgrown and above the waterline.

Nunney Castle moat

The moat around Nunney Castle had filled with green algae due to problems with the weir

English Heritage is responsible for maintenance of Nunney Castle, including the moat. The Environment Agency manages the Nunney Brook and only gets involved in issues surrounding the moat if fish are starting to die through a lack of oxygen.

English Heritage started work to replace the weir on Monday 7 October. Huge new boulders and planks were firmly fixed in place to create a sturdy new weir.

Eel ladder

Delay to the replacement project was caused by an EU Directive that makes it compulsory to install an eel ladder on the weir. This led to substantial additional costs that will be borne by English Heritage.

English Heritage

The existing weir is constructed of large boulders that have gradually been washed away.

An eel ladder is type of fish ladder designed to help eels swim past barriers, such as dams and weirs or even natural barriers, to reach upriver feeding grounds.

The basic design of an eel ladder has the eel swim over the barrier using an eel ascending ramp, which provides the eels a climbing substrate to ‘push against’ while slithering upstream.

An eel ladder typically consists of four parts: an eel ascending ramp, a supporting structure, a water-feeding system, and a side gutter. The side gutter provides an attraction flow to draw eels toward the ladder, the water-feeding system ensures the proper flow of water to the gutter and the ramp, and the supporting structure mounts the ladder to the barrier.

Nunney Brook weir

The new weir with eel ladder

Excellent trout and eels

Although there is currently little or no fish in the Nunney Brook – unlike the moat, which is well-stocked -, the Nunney Brook certainly used to have trout and eels in it.

The Rev. John Collinson wrote in his 1791 book The History and Antiquities of the County of Somerset: “A spring rises called Holywell or Holwell from which a brook runs through Nunney. This stream contains excellent trout and eels and has a bridge of three arches over it in the street of Nunney village through which it runs.”

Eel and mash shop

Eels were long a popular delicacy in the UK

The eels’ spawning grounds are believed to be in the Sargasso Sea resulting in a 4,000 mile migration from the UK. Once spawned, eel larvae are carried by oceanic currents back to continental shores.

Here they are distributed into waterways throughout Europe. By this stage they have transformed from the flat, leaf-like shape of the larvae to a small transparent eel known as glass eels.

Eel stocks

Eel stocks have dwindled in recent years

As unpigmented glass eels or newly pigmented elvers, they enter UK estuaries with the spring tides in Spring, migrating upstream into freshwater where they stay and mature for up to 20 years.

Eel stocks have dwindled in recent years due to increases in man-made structures acting as barriers to migration upstream, a reduction in freshwater habitat, pollution, fisheries, changing oceanic currents and exposure to parasites.

Jellied eels were a traditional delicacy in the UK until the Second World War. Today, Japan consumes more than 70 percent of the global eel catch.

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