Lake Bassenthwaite is home to rare species of fish

Bassenthwaite Lake is one of only two lakes in the country to have populations of vendace.

But scientists say too much silt is entering the waters and could hinder the breeding of the fish.

A team is taking samples from under the lake bed to find out what is happening and whether it can be prevented.

Lake Bassenthwaite is a designated Site of Special Scientific Interest and National Nature Reserve.

It is home to the vendace which is one of the UKs rarest fish and feeds primarily on free-swimming organisms such as water fleas. It is protected under the Wildlife and Countryside Act (1981).

But increasing amounts of sediment are finding their way into the water hampering the breeding of the vendace.

Breeding grounds

Professor Barbara Maher, who is taking part in the project, said a specially-designed bore will be sunk 15 metres below the lake bed from where samples will be taken.

She said: "There are only two populations of vendace in the country - at Bassenthwaite and Derwent Water.

"There used to be two populations in Scotland but both have been reported extinct since1951."

She said the fish needs shallow water to raise eggs and the gravely lake floor is ideal.

"But at the moment there is too much fine grain sediment coming in so it is silting up the fish breeding grounds.

"The silt also brings in nutrients which may be responsible for bacterial blooms causing the water to darken up and the amount of oxygen to reduce.

"We want to find out why it is happening and what we can do to stop it."