Alosa alosa | Allis Shad



Conservation status

Future ProspectsN/A
Overall  Assessment of Conservation StatusN/A
Overall Trend in Conservation StatusN / A

*Only small numbers of this species are caught in Irish marine waters. There is also evidence of small numbers entering Irish freshwaters. It is currently considered a vagrant for the purpose of Habitats Directive Article 17 reporting

Sources: King, J. J.; Roche, W. K., 2008; NPWS 2013; European Topic Centre on Biological Diversity.

IUCN Conservation Status

Ireland  (1)
Data Deficient
Europe (2)Least Concern
Global (3)Least Concern
Sources: (1) King, J.L. et al 2011; (2) Freyhof, J. 2008; (3) Freyhof, J. & Kottelat, M. 2008.

Legal status

Protected by the following legal instruments:

  • Habitats Directive [92/42/EEC] Annex II, Annex V
  • Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention)  Appendix III
  • The Convention for the Protection of the marine Environment of the North-East Atlantic (OSPAR)
  • 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; Froese, R. and D. Pauly. eds., 2014.

Native status

The 2008 IUCN Global and European Red List assessment accounts for this species list Ireland as one of the countries where it is native, however for the purposes of Habitats Directive Article 17 reporting for the period 2007-2012 it is considered a vagrant in  Ireland.

Sources: Freyhof, J. 2008; Freyhof, J. & Kottelat, M. 2008; NPWS.

Alosa alosa has been recorded in Irish coastal waters during the marine phase of its life-cycle, but in low numbers. It has also been recorded in Irish freshwater, but again in low numbers. Current indications of spawning comes, in addition to physical examination of breeding age individuals, from the presence of Twaite shad x Allis shad hybrids rather than the detection of juvenile Allis shad (Alosa alosa).

Sources: King, J. J., Roche, W. K., 2008; NPWS 2013.

Species Biology


Allis Shad (Alosa alosa) very closely resembles the related Twaite Shad (Alosa fallax) and can only be reliably distinguished from it by counting its gill rakers. Allis Shad is generally slightly larger than Twaite Shad.

Source: Davies et al (2004).

  • Adult average length 45-50 cms
  • Maximum weight recorded; 4kg
  • Females usually larger than males (max recorded length female; 83cms, male (?); 69cms.
  • One dorsal fin, no adipose fin.
  • Barbels not present on head.

  • Dorsal and caudal (tail) fins distinct and separate.
  • Lateral line absent
  • Eyelids obvious.
  • Usually more than 90, fine, gill rakers on the first gill arch.

  • Body deep (deeper than head length at pectoral fin) and somewhat laterally compressed.
  • Lower jaw fits into notch in upper jaw.
  • Scales are large and thin.
  • Keeled ridge of scales along the belly giving a spiny look and feel there.
  • Colouration; Dark blue dorsally, golden on upper sides fading to silver ventrally.
  • Markings; Usually with a dark spot behind gill cover, occasionally up to six more behind this but these markings may be absent.
Hybrids between Twaite Shad (Alosa fallax) and Allis Shad (Alosa alosa) are known so individuals with features intermediate between both may be encountered (e.g. more than 60 but less than 90 gill rakers).

Sources: Maitland, Peter S., 2004; Maitland P.S. & Hatton-Ellis T.W. 2003; Froese, R. and D. Pauly. eds., 2014.



The Allis shad (Alosa alosa) is anadromous spending most of its life at sea but returning to freshwater to spawn. It is neritic-pelagic for most of its life, but when ready to mate the species congregates in estuaries before migrating into freshwater rivers.

Source: Froese, R. and D. Pauly. eds., 2014.

Habitats include but are not necessarily limited to;

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

Sources: Froese, R. and D. Pauly. eds., 2014.; Fossitt, J.A. 2001.


  • Sexual maturity males: c. 4 years
  • Sexual maturity females: c.5 years
  • Adults migrate to freshwater for spawning  April - May.
  • Spawning May-June
  • 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 6-8 days.
  • Juveniles begin to migrate seawards from 10 months.
  • Mature at c. 3-4 years.
  • Maximum recorded age: 10 years.

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

Threats faced

In the Article 17 Habitats Directive reporting for the period 2007-2012 no Threats were listed for this species.

Source: NPWS 2013.

In the 2011 Irish Red List of Amphibians, Reptiles & Freshwater Fish a potential threat to the species in it's marine phase is suggested;

  • By-catch in commercial fishery activities
Source: King, J.L. et al 2011.

The 2008 IUCN Global and European level Red List assessment accounts for this species list the following threats;

  • Overfishing
  • Pollution
  • Cutting off access to spawning sites.

Sources: Freyhof, J. 2008; Freyhof, J. & Kottelat, M. 2008.

Conservation actions

In the Article 17 Habitats Directive reporting for the period 2007-2012 no Conservation Measures in place or being implemented were listed for this species.

Source: NPWS 2013.

In the 2007 European Regional IUCN Red List assessment for Alosa alosa, in addition to acknowledging legal protection under the Berne Convention and Habitats Directive, the assessment also referred to the use, in France, of the following Conservation Action;

  • Fish passes and elevators to allow access to spawning sites.

Sources: Freyhof, J. 2008.


World distribution(GBIF)

A species of the east North Atlantic, found in coastal waters from Norway to northern Mauritania and in large rivers that flow into those coastal waters.

Source: Froese, R. and D. Pauly. eds.

Accuracy of world distribution shown in the Global Biodiversity Information Facility (GBIF) map below will be constrained by, amongst other factors, data held but not shared by countries and organizations not participating in the GBIF.

Irish distribution

The species has been recorded in rivers in the south west, south, south-east and north-east and in coastal waters. There is some indication that the species has spawned in some south eastern rivers, where a hybrid between it and the Twaite Shad (Alosa fallax) has been recorded.

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

Temporal change

Records submitted to Data Centre in 2021

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 the Allis Shad 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:

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



Aprahamian M.W., Baglinière J.L., Sabatié R., Alexandrino P. and Aprahamian C.D. (2002). Alosa alosa and Alosa fallax spp.: Literature review and bibliography. Environment Agency R&D Technical Report W1-014. Environment Agency,

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

Fossitt, J.A. (2001) A Guide to Habitats in Ireland. The Heritage Council.

Freyhof, J. 2008. Alosa alosa. The IUCN Red List of Threatened Species. Version 2014.2. <>. Downloaded on 16 October 2014.

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

King, J. J.; Roche, W. K., 2008: Aspects of anadromous Allis shad (Alosa alosa Linnaeus) and Twaite shad (Alosa fallax Lacepede) biology in four Irish Special Areas of Conservation (SACs): status, spawning indications and implications for conservation designation. Hydrobiologia 602, 145–154.

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.

Maitland P.S. & Hatton-Ellis T.W. (2003).Ecology of the Allis and Twaite Shad. Conserving Natura 2000 Rivers Ecology Series No. 3. English Nature, Peterborough.

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.

Additional comments

The Allis shad (Alosa alosa), along with its sister species the Twaite shad (Alosa fallax), has experienced a grave decline in abundance in the past century or so, throughout its range. These declines have been attributed to a combination of overfishing, pollution and anthropogenic barriers to spawning sites.

For the Allis shad it is not currently clear whether it has ever spawned successfully and regularly in Irish freshwaters.

There are recent indications of hybridization between the Allis shad and Twaite shad in Irish freshwaters. This may be a result of the 'pooling' of both species below obstacles such as dams and weirs. Such hybridization may prove deleterious to both species, the Allis shad perhaps most affected as it is the less numerous of the two species.

Sources: King, J. J., Roche, W. K., 2008; Maitland P.S. & Hatton-Ellis T.W., 2003; Aprahamian M.W. et al 2002.