Twaite shad (Alosa fallax)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help

Summary

Description

Alosa fallax is a member of the herring family. It is a planktivorous fish with silvery white sides and a deep blue colouration on its back. It is most commonly recorded at a size between 20-40 cm but has been reported to reach 60 cm. Like other shads its upper jaw is distinctly notched in the mid line and the gill cover has distinct radiating ridges.

Recorded distribution in Britain and Ireland

A coastal species recorded from many areas around the British Isles. Known spawning populations exist in a few rivers flowing into the Severn estuary with other possible spawning sites in southwest England and the Solway Firth.

Global distribution

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Habitat

Coastal waters returning to freshwater to spawn usually above shallow gravel substrates near deeper pools. It is a schooling and migratory species and spends most of its life offshore.

Depth range

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Identifying features

  • Dorsal profile of the twaite 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.
  • Large thin scales and scutes found along belly.
  • Dark spot behind the gill cover (sometimes absent).
  • Grows up to 50 cm in length.

Additional information

The twaite shad is distinguished from the other European shad, the allis shad (Alosa alosa), by having between 40-60 gill rakers on the first gill arch while Alosa alosa has between 80-130 (Whitehead, 1985). The twaite 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 (Muus & Nielson, 1999).

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Further information sources

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Bibliography

  1. Froese, R. & Pauly, D., 2007. Fishbase. A global information system on fishes. [On-line] http://www.fishbase.org, 2008-02-18

  2. Hayward, P.J. & Ryland, J.S. (ed.) 1995b. Handbook of the marine fauna of North-West Europe. Oxford: Oxford University Press.

  3. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  4. Muus, B.J. & Nielsen, J.G. 1999. Sea Fish. Scandinavian Fishing Year Book. Hedehusene: Denmark

  5. Whitehead, P.J.P. 1985. Clupeoid Fishes of the World: An Annotated and Illustrated Catalogue of the Herrings, Sardines, Pilchards, Sprats, Shads, Anchovies and Wolf-herring; Part 1 - Chirocentridae, Clupeidae and Pristigasteridae. FAO, 125. Rome, Italy.

Datasets

  1. Cofnod – North Wales Environmental Information Service, 2018. Miscellaneous records held on the Cofnod database. Occurrence dataset: https://doi.org/10.15468/hcgqsi accessed via GBIF.org on 2018-09-25.

  2. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  3. Norfolk Biodiversity Information Service, 2017. NBIS Records to December 2016. Occurrence dataset: https://doi.org/10.15468/jca5lo accessed via GBIF.org on 2018-10-01.

  4. OBIS (Ocean Biodiversity Information System),  2025. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2025-05-21

  5. South East Wales Biodiversity Records Centre, 2018. SEWBReC Fish (South East Wales). Occurrence dataset: https://doi.org/10.15468/htsfiy accessed via GBIF.org on 2018-10-02.

  6. Suffolk Biodiversity Information Service., 2017. Suffolk Biodiversity Information Service (SBIS) Dataset. Occurrence dataset: https://doi.org/10.15468/ab4vwo accessed via GBIF.org on 2018-10-02.

Citation

This review can be cited as:

Barnes, M.K.S. 2008. Alosa fallax Twaite shad. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-05-2025]. Available from: https://www.marlin.ac.uk/species/detail/48

Last Updated: 27/03/2008