Taxonomy

Alosa fallax | Twaite Shad

Distribution

Status

Conservation status

HABITATS DIRECTIVE ARTICLE 17 REPORTING
Range
Bad
Population
Inadequate
Habitat
Inadequate
Future Prospects
Inadequate
Overal Assessment of Conservation Status
Bad
Overal trend in Conservation Status*
Stable

Source: NPWS 2013.


IUCN Conservation Status
Ireland (1)
Vulnerable  [D2]
Europe (2)
Least Concern
Global (3)
Least Concern

Sources: (1) King, J.L. et al 2011; (2) Freyhof 2008; (3) Freyhof, J. & Kottelat, M. 2008.




Legal status

Protected by the following legal instruments:

  • EU Habitats Directive [92/43/EEC] Annex II and V.
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention) Appendix III.
  • Fisheries Acts 1959 to 2006.
  • Fisheries Act (Northern Ireland) 1966.
  • Foyle Fisheries Act (NI) 1952.
  • Foyle and Carlingford Fisheries Act 2007
Sources: King, J.L. et al, 2011; Maitland, Peter S., 2004.

Native status

Native.

Species Biology

Identification

  • One dorsal fin, no adipose fin.
  • Barbels not present on head.
  • Dorsal and caudal (tail) fins distinct and separate.
  • Lateral line absent.
  • Eyelids obvious.
  • Lower jaw fits into notch in upper jaw.
  • Keeled ridge of scales along the belly giving a spiny look and feel there.
  • Usually less than 60 gill rakers on the first gill arch.
  • Usually less than 70 scales in the main lateral  row of scales.
  • Colouration; Overall silvery, with green-blue tinge dorsally, mainly silver laterally, ightening considerably to white ventrally. Usually has a number of large, dark spots laterally in front half. Dark spots may be difficult to see or may be absent.
  • Length at maturity; 25-40cm.

  • Normal life span 5-9 years.

Hybrids between Twaite Shad (Alosa fallax) and Allis Shad (Alosa alosa) are known so individuals with features intermediate between both may be encountered.

Source: Maitland, Peter S., 2004.



Habitat

The Twaite Shad (Alosa fallax) is anadromous spending most of its life at sea but returning to freshwater to spawn. 

Habitats include but are not necessarily limited to*;

  • Marine water bodies (M)
  • Depositing / lowland rivers (FW2)

Sources: fishbase.org; Fossitt, J.A. 2001.

*subspecies killarnensis only occurs in Lough Leane in Killarney. See separate profile for that taxon.

Sources: Maitland, Peter S., 2004; Fossitt, J.A., 2001.

Reproduction

  • Sexual maturity males: c. 4 years
  • Sexual maturity females: c.5 years
  • Adults migrate to freshwater for spawning  April - May.
  • Most adults die after spawning but c. 5-6 % may return to spawn again.
  • Spawning is nocturnal, fertilisation in the water column after which fertilised eggs sink to river-bed.
  • Eggs hatch within 4-8 days.
  • Juveniles begin to migrate seawards from 3-4 months.

Sources:Froese, R. and D. Pauly. eds., 2014.; Davies et al, 2004.

Threats faced

THREAT
ARTICLE 17 CODE
RANKING
Invasive non-native species*
I01
High
Fishing and harvesting aquatic resources
F02
High
Reduced fecundity/ genetic depression in animals (inbreeding)**
K05.01
High

* competition for resources with, and direct predation by, alien invasives such Asian Clam (Corbicula fluminea) and competition with introduced coarse fish species.

** due to hybridisation with A. alosa.

Source: NPWS 2013.


Conservation actions

In the Article 17 Habitats Directive reporting for the period 2007-2012 Conservation Actions in place or being implemented during the period were;

  • Continued legal protection of the species and its habitats inside and outside of Natura 2000 sites.

Source: NPWS 2013.


Distribution

World distribution(GBIF)

Western Europe, Norway to the Mediterranean including Ireland and Britain.

Sources: Maitland, Peter S., 2004.

Irish distribution

Coastal marine waters and recorded from Munster Blackwater, Suir, Barrow, Nore and Slaney and Boyne estuary. Subspecies killarnensis only occurs in Lough Leane in Killarney. See separate profile for that taxon.

Source: King, J.L. et al 2011.

Temporal change

Records submitted to Data Centre in 2024

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

The National Biodiversity Data Centre is trying to improve our knowledge on the distribution of Alosa fallax in Ireland. Should you observe the species, please submit sightings to add to the database. Detailed observations will assist us gaining a better insight into where the species is most abundant in Ireland and we might also be able to detect regional variations. Please submit any sightings and photographs at:

http://records.biodiversityireland.ie/index.php

All records submitted on line can be viewed on Google Maps – once checked and validated these will be added to the database and made available for conservation and research.

Further information

For further information contact Dr. Liam Lysaght llysaght@biodiversityireland.ie

References

Publications

Davies, C.E., Shelley, J, Harding, PT, McLean, IFG, Gardiner, R, Peirson, G (2004), Freshwater fishes in Britain - the species and their distribution. Harley Books

Freyhof, J. 2008. Alosa fallax. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 18 December 2014.

Freyhof, J. & Kottelat, M. 2008. Alosa fallax. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 18 December 2014.

Froese, R. and D. Pauly. Editors. 2014. FishBase. World Wide Web electronic publication. www.fishbase.org, version (11/2014).

King, J.L., Marnell, F., Kingston, N., Rosell, R., Boylan, P., Caffrey, J.M., FitzPatrick, Ú., Gargan, P.G., Kelly, F.L., O’Grady, M.F., Poole, R., Roche, W.K. & Cassidy, D. (2011) Ireland Red List No. 5: Amphibians, Reptiles & Freshwater Fish. National Parks and Wildlife Service, Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.

Maitland, Peter S., 2004. Keys to the Freshwater Fish of Britain and Ireland With Notes on Their Distribution and Ecology. The Freshwater Biological Society, Cumbria.

NPWS (2013) The Status of EU Protected Habitats and Species in Ireland.  Species Assessments Volume 3. Version 1.0. Unpublished Report, National Parks & Wildlife Services. Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland.

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