Allis Shad Alosa alosa
A herring-like, planktivorous fish with silvery white sides and a deep blue colouration on its back. The Allis Shad is a coastal species recorded from many areas around the British Isles. Known spawning populations exist in the River Tamar with other possible spawning sites in the English and Bristol Channels and the Solway Firth. Image: Koelner50 (WikiMedia).