FAMOUS as the inspiration for one of England’s greatest artists – John Constable – the River Stour is a much-loved regional landmark.

Running through the Dedham Vale, the river passes through an area of outstanding natural beauty - as James Marston discovered.

Peaceful and serene, the River Stour is home to a wide variety of wildlife. But underneath the surface is an ecosystem that is crucial to the river’s ecology and the area’s biodiversity.

And in front of the historic Flatford Mill, it was science, not art, that is taking centre stage. A flat-bottomed boat was criss-crossing the mill pool, closely watched by a few tourists and a couple of curious ducks.

Andrew Raine, a team leader with the Environment Agency, was at the scene. He said: “Today we are conducting fish surveys. It’s called electrofishing, we pass a current through the water which stuns the fish and enables us to net them.”

Once caught, the fish are recorded, measured and weighed and a scale sample is taken – this enables the agency to record the age of the fish.

The fish surveys have been taking place on the Stour, and other Suffolk rivers since the 1960s.

Today Suffolk has some of the most comprehensive records of fish stocks in the UK.

Andrew said: “Electrofishing enables us to assess the health of the fish, the river and the local ecosystem. It doesn’t harm the fish in any way.”

Responsible for the country’s rivers, the Environment Agency has been much in the news as floods have struck across the UK.

Andrew said: “We thought this year we would be worrying about low water levels with the drought, but the rain has changed that.

“Our job is to check for pollution, check water quality and flow levels.”

Downstream from the iconic Willy Lott’s cottage – the lower Stour – the team has been recording healthy fish stocks.

The most common species include roach, perch, dace, pike and eel.

Dan Hayter, a monitoring officer for the Environment Agency, said: “We are looking at all species of fish and eels.

“We have about 30 sites on the Stour that we monitor and we do a survey every three years.

“So far we have found that fish stocks are better than previous years; this reflects the health of the river.

“We did suspect a natural toxin in the lower Stour and our surveys were showing up lower fish stocks, but this year it looks as if things have improved quite a bit.”

The UK’s rivers are, in general, far healthier today than they have been for decades.

Dan said: “Biodiversity around here is quite good.

“We see lots of other animals including water voles, kingfishers, egrets, the common tern, heron, swans and ducks and the occasional otter.

“We also see mink, which were first released into the wild from a mink farm in the Waveney area back in 1953. We are trying to eradicate them.”

Once the survey is completed, the agency publishes a report which is crucial to anglers, conservationists and leisure users of the river.

Dan said anglers want to make sure the river is well-stocked before deciding to fish there.

After a few minutes sweeping the mill pond the team came back to the riverbank with several fish in a holding tank including a female pike weighing about eight pounds and a yellow eel.

Andrew said: “Young eel numbers of have fallen by 80-90 per cent in the last decade.

“They breed in the Sargasso sea near Bermuda and make their way to England’s rivers crossing distances of thousands of miles.”

Dan said the team will be continuing their work on the Stour for some days.

He said: “It is a lovely job on a day like this, it is quite physical and it is great to be outdoors. It’s not so good in the rain.”

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