Creating refuge for fish on a depleted river – the Charvil Meadows project

To a casual observer the River Loddon at Charvil Meadows may feel like a wild and diverse part of the river. In this part of the Loddon large woody material can be found in abundance. Stands of trees line the banks and cast patches of dappled shade that cool the river in the hot summer months and create lots of small refuges that fish could hide amongst to escape from predation.

Unfortunately, from evidence collected from the Loddon at Twyford this isn’t the case. As part of the project we carried out an electro-fishing survey with Martin Moore and the Loddon Fisheries and Conservation Consultative (LFCC) to use as baseline data.  Along a short stretch of river that should support hundreds of fish, we only caught 37 individuals, and 13 of those were made up of minnow and bullhead. The same survey recorded few mature fish and only a a small number of chub and dace, which are normally indicators of a healthy river.

The Loddon at Charvil Meadows is downstream of the first major barrier to fish migration so we knew the depleted fish population was not caused by a access to the stretch being blocked. It was a worryingly clear demonstration that our rivers may not be in as good as condition as they appear.

The presence of the occasional braided channel, gravel bar and decent riffle habitat should support somewhat healthy fish populations. However, the closer you look the more you realise that large scale historic changes have affected the river in some of the most fundamental ways.

Regular dredging over hundreds of years has almost completely disconnected the river from its floodplain for much of the year, and means that the river has become almost continuously a single or braided channel along its length. The incised channel drains the land around it and reduces the habitat suitability for freshwater macro-invertebrates in most areas outside of the main channel – invertebrates which fish are heavily reliant on for food.

There is also chronic pollution from a range of substances including pesticides, oils, heavy metals and sewage. All of these can suppress the populations of fish within a river until a large acute pollution event causes a mass die-off of fish.

So how do we go about reversing these losses?

Well, it will take a lot of concerted effort across the entire landscape, but we can start with small scale interventions to return some of the missing habitat.

And that is what we have done on the River Loddon at Charvil Meadows.

Over a two-week period in late September/early October, we were busy converting an area of grassland, owned by Wokingham Borough Council, in the north eastern corner of Charvil Meadows, into a backwater habitat. This essentially means we have created a large pool, adjacent and connected to the river, which will act as a refuge.

The backwater has been designed so that during a large pollution event the water within the backwater will remain largely clean, providing a safe haven until for all manners of wildlife to take sanctuary until the pollution has passed. Additionally, the stillwater habitat which has been created will allow fish to take shelter during floods, and prevent them from being ‘washed out’ of the system.

This shallow pool will provide ideal habitat for fish fry to develop in during the warmer months. Large pieces of wood have been dug into the banks to provide additional shelter and habitat.

We excavated c.1000 tonnes with the help of R.Collards and graded the banks to create a small marginal shelf under the water in such a way that native aquatic plants will blossom and burst into life in the spring. We’ve sown a native mix of aquatic and semi-aquatic seeds around the site and will do so again in the spring to help native plant species thrive.

The project was designed and delivered in house by staff from South East Rivers Trust with help and expertise in the form of Ben the digger driver from Kenward Groundworks. We were incredibly lucky with largely grey but dry weather for much of the delivery and we managed to finish on site before any heavy rain set in.

We kindly received permission from a landowner local to Twyford village and their tenant farmer for access through their field, without which this project would not have been successful.

We gained a lot of interest in the project with interviews on Radio Berkshire and were filmed by BBC South East. It also made it onto Radio 4’s Farming Today.

The creation of this backwater was funded by a generous grant from the Loddon Fisheries and Conservation Consultative as part of an Enforcement Undertaking by Thames Water for pollution event(s) and supported by the landowner Wokingham Borough Council and the Environment Agency. A big thank you is also due to Martin Moore for volunteering his time and services with the electrofishing survey.