Rising temperatures a threat to Norfolk rare river species

Dr Jonah Tosney from the Norfolk Rivers Trust has been checking the health of fish in the county's rivers

The current heatwave is threatening rare and protected species which live in rivers, an ecologist has said.

Dr Jonah Tosney from the Norfolk Rivers Trust said higher water temperatures and low river levels can harm things like the bullhead fish and crayfish.

The Met Office has issued an extreme heat weather warning for England from Sunday until Tuesday.

Dr Tosney said: "The warmer the water gets the less oxygen it can hold so that's a huge threat to them."

Both the bullhead and white-clawed crayfish are on the International Union for Conservation of Nature (IUCN) red list of threatened species.

Temperatures in the UK are expected to peak on Tuesday, with highs of 36C (96.8F) forecast.

Dr Jonah Tosney said demand for water also affected river levels

Dr Tosney said: "The actual water temperature can be a threat, once that gets about 20C all these species that are evolved to live in cool streams - that's a real danger to their life.

"The other thing that's going on is the less water we've got, the more the concentration of pollutants build up.

"The water evaporates off and that's just leaving everything behind it."

Heatwaves are becoming more likely and more extreme because of human-induced climate change.

The River Glaven near Holt in Norfolk has low levels due to the heatwave and lack of rain