The descriptive text, below the map, is from the Cornish Red Data Book (2009). The map on this web page depicts the organisms distribution and shows the records made pre-2000 and those made since.
Habitat & Distribution
An anadromous species that is strongly migratory. It is found in inshore waters and enters the rivers in spring when water temperatures reach 10-12\'baC and penetrates far upstream to spawn, normally only once, on stony ground, returning soon after to the open sea. On the Tamar they die, the spent corpses can be seen below the spawning grounds. They occur all around the coast of Britain with the main concentration being in the Thames estuary, Bristol Channel and around south-west England. Allis Shad are known to spawn in the lower reaches of the River Tamar, downstream of Gunnislake Weir and in associated rivers. They can be quite common in the Falmouth Bay and Estuary area in springtime. This species is found along the Atlantic coast from the Mediterranean to Scandinavia.
This species has been in decline since the mid-nineteenth century, due to interruption of its spawning migration resulting from obstructions along the various river courses. Deterioration of water quality as a result of agricultural and industrial pollution has also played a part. Many specimens are accidentally caught in nets, set for other fish species, in the open sea.
Listed under Appendix III of the Bern Convention; listed under Annex IIa and Va in the EC Habitats Directive; It is also protected under Schedule 5 of the Wildlife and Countryside Act (1981), S.9 (1) \endash 1991, S.9 (4) (a) \endash 1998, against killing, injuring or taking. It is also on the UK List of Priority Species with its own Species Action Plan (SAP) and is an OSPAR priority and NIMF candidate species.
I.J. Bennallick, S. Board, C.N. French, P.A. Gainey, C. Neil, R. Parslow, A. Spalding and P.E. Tompsett. eds. 2009. Red Data Book for Cornwall and the Isles of Scilly. 2nd Edition.Croceago Press.
The Cornish Red Data Book Project was led by the Cornwall and Isles of Scilly Federation for Biological Recorders (CISFBR). The full text and species accounts (minus the maps) are available on the CISFBR website.