Biodiversity & Conservation

Allis shad - Alosa alosa

Alosa alosa

Image Keith Hiscock - Alosa alosa caught off Plymouth. Image width ca 40 cm.
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Distribution map

Alosa alosa recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

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  • Berne
  • EC_Habitats
  • WC_Act_1981
  • UK_BAP
  • OSPAR
Taxonomy icon Taxonomy Taxon English term
Phylum Chordata Sea squirts, fish, reptiles, birds and mammals
Class Actinopterygii Ray-finned fish, e.g. sturgeon, eels, fin fish, gobies, blennies, and seahorses
Authority (Linnaeus, 1758)
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland 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.
Habitat information icon Habitat information Coastal waters returning to freshwater to spawn above gravel substrates. Alosa alosa has been reported in depths ranging from 10 -150 m.
Text page icon Description Alosa alosa is a herring-like, planktivorous fish with silvery white sides and a deep blue colouration on its back. It is most commonly recorded at a size between 30 -50 cm but has been reported to reach 70 cm. Like other shads its upper jaw is distinctly notched in the mid line and the gill cover has distinct radiating ridges.
Identifying features
  • Dorsal profile of the allis shad is curved and the tail fins are forked.
  • Body flattened side to side with strong spines along the belly.
  • Deep bodied with silvery scales.
  • Back deep blue in colour with silvery white sides.
  • Dark spot behind the gill cover (sometimes absent).
  • Grows up to 70 cm length.
Additional information icon Additional information The allis shad is distinguished from the other European shad, the twaite shad (Alosa fallax), by having between 80-130 gill rakers on the first gill arch while Alosa fallax has between 40-60. The allis shad is 'anadromous' in that it spends its life in the ocean but enters rivers in April and May to spawn before returning to the sea. Juveniles remain in the rivers for up to 24 months.

This review can be cited as follows:

Al Reeve 2005. Alosa alosa. Allis shad. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 11/09/2010]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=2465>