A clean-up operation is continuing on the River Wensum after more than 3,000 fish died along a stretch of river in Norwich. Experts say mass fish deaths could become increasingly frequent because of climate change after thousands perished in what has been described as a river heatwave "disaster".
Norfolk Wildlife Trust issued the warning following an incident on the River Wensum in Norwich last Thursday. The Environment Agency believed it was caused by heavy rainfall flushing contaminants from surface water drainage systems into the river at a time when it was already suffering from depleted oxygen levels caused by prolonged dry, hot weather.
Helen Hebditch, director of nature recovery at the Norfolk Wildlife Trust, called the conditions a "recipe for disaster".
"In a summer characterised by shocking wildfires, this is yet another example of how our changing climate is having a devastating impact on our wildlife.
"Drought conditions are depleting already low water levels, and sustained high temperatures lower water oxygen levels, leaving river wildlife such as fish struggling to breathe.
"This means our rivers, and the wildlife that calls them home, are extremely vulnerable. Add to this heavy rain washing pollutants into the water from nearby roads or sewage discharge, and it's a recipe for disaster."
The stretch of the River Wensum where the fish were discovered is a popular spot for paddle boarders and people using canoes, with multiple hire firms located in the city.
Hebditch said the incident was "particularly significant" because the River Wensum is a protected chalk river. She added that such events will likely increase in frequency because of climate change.
There have also been reports of fish found dead elsewhere in the county on the River Yare in Trowse and at Cantley east of Norwich.
Anglian Water workers continue to clean up the Wensum, and Norwich City Council and the Broads Authority are also assisting.
Council workers said they had collected about 1,200 fish in two days, focusing on larger species, while Anglian Water said it has collected 2,126.
People have complained there has been a strong smell along the river in the past few days.
Anglian Water, which is continuing to monitor the river, said ammonia levels have returned to background levels and dissolved oxygen levels are improving.
The River Wensum stretches about 44 miles (71km) through Norfolk and is designated as a Site of Special Scientific Interest and Special Area of Conservation.
It is believed to be home to more than 100 plant species and rich invertebrate fauna, and is recognised as one of the most important chalk river habitats in England.
Do you have a story suggestion for Norfolk? Contact us below.
Follow Norfolk news on , Facebook, external, Instagram, external and X, external.
Hundreds of dead fish in river linked to heatwave
River fading before our eyes, say campaigners
Related internet links
Anglian Water workers collected thousands of dead fish from the River Wensum in Norwich
Lots of smaller fish remain caught in weeds in the river
Dead fish continue to be found in the river, such as at Pulls Ferry
