SALMON from the chalk streams of Hampshire are genetically unique, researchers have discovered.

The fish are classified as Atlantic salmon but research by the University of Exeter and the Fordingbridge-based Game and Wildlife Conservation Trust shows their genes are distinct from others of the species.

The researchers studied five chalk streams in Hampshire and Dorset - habitats they said were under “massive pressure” from human activity.

Classifying chalk-stream salmon as a separate sub-species could make it easier to protect them.

Chalk streams - which originate in chalk hills and are generally wide and shallow with clear water - are fed by underground aquifers.

As a result they have steadier flow rates and more stable temperatures than most other rivers and are less acidic.

Of the 161 rivers classified as chalk streams by the Environment Agency, only five contain significant populations of salmon.

These - the Frome, Piddle, Avon, Test and Itchen - were the focus of this study.

Chalk-stream salmon, like other species, spend long periods at sea and swim hundreds of miles but return to breed.