Rising water temperatures indicate local climate change

Water in the lake reached 24C in July,the hottest since records began in 1933, according to the Freshwater Biological Association.

The trend is also taking its toll on native fish populations.

Roger Sweeting, the association's director, said the rising temperature was an indication of climate change.

He said: "We've been taking readings every day for 73 years. For the last 15 of those years we've had hot temperatures throughout the year.

Northerly water

"Over the last 15 years it's been much warmer than the long term average - compared to 1961 and 1990.

"Fish being cold blooded, their activity reflects the water temperature. Roach, which were introduced some years ago, like warmer water and are now probably the most common fish in the lake.

"But native species such as the arctic char need cooler, more northerly water and are at the edge of their tolerance."

In a world where water is a scarce resource, the effects of climate change will compound this problem and also affect the quality of water, added Mr Sweeting.