The twait shad or twaite shad (Alosa fallax) is a species of fish in the family Alosidae.[1] It is found in the eastern Atlantic Ocean and the Mediterranean Sea and is an anadromous fish which lives in the sea but migrates into fresh water to spawn. In appearance it resembles an Atlantic herring but has a row of six to ten distinctive spots on its silvery flanks. They become mature when three or more years old and migrate to estuaries, later swimming up rivers to spawn. Populations of this fish have declined due to overfishing, pollution and habitat destruction. Conservation of this species is covered by Appendix III of the Bern Convention and Appendix II and V of the European Community Habitats Directive.
The twait shad is a typical herring-type fish and much resembles the allis shad. It has no lateral line and the belly is more rounded than that of the sprat and Baltic herring. The gill cover is ridged and the caudal peduncle has large, plate-like scales. This fish is more colourful than the Baltic herring. The back is a bluish green colour and the head brownish with a golden tinge on the operculum. The flanks are silvery, sometimes with a bronzy tinge, and there are a distinctive row of six to ten large dark spot just behind the gill cover though these may fade when the fish is dead. The adult length is typically 25 to 40 cm (10 to 16 in).[2]
Distributionedit
The twait shad is found in most of Europe and all countries bordering the Mediterranean Sea.[1]
Biology and lifecycleedit
Alosa fallax has a similar lifecycle to A. alosa (allis shad). They are known to live in sympatry.[3] Some studies have suggested A. fallax and A. alosa species can hybridize.[4] They are anadromous species, like many other species in the genus Alosa.[4] However, some record of them being landlocked suggests an ability to adapt well to their environment.[4] They primarily live at sea on feeding grounds and migrate to their spawning grounds between April and June once they are sexually mature.[4] Maturity usually ranges from 3–7 years of age.[4] Juveniles appear in estuaries and brackish water around June to July.[3] The salinity of brackish water may pose problems to the juveniles migrating from fresh water.[3]
Population reductionedit
Populations have been reduced primarily through overfishing, pollution, habitat destruction and migratory route obstruction in the Victorian Era.[5][4] Hybridization between species is more likely with species affected by human disturbances.[4] It is estimated that the estuarine phase, or the time that they are in the estuaries migrating from spawning grounds to sea, has a duration in A. fallax of up to a year and a half.[3] The estimate, however, does not take into account individual variation and survival of juveniles in the estuarine phase.[3]
Conservationedit
Four special areas of conservation have been designated in Ireland where Alosa species have been known to spawn.[4]Alosa fallax "has been placed in Appendix III of the Bern Convention (1979) that lists protected fauna species as well as in appendix II and V of the European Community Habitats Directive (1992) that list, respectively, species whose conservation requires the designation of special areas of conservation and that are subject to management measures."[3]
In England the Unlocking The Severn project, a consortium of the Canal & River Trust, Severn Rivers Trust, Environment Agency and Natural England is creating fish passes around weirs on the River Severn. The aim is to open 150 miles (241 km) of the river for the fish to increase its freshwater breeding habitat. By 2021 passes at Diglis and Bevere, near Worcester, had been completed,[6] and by 2022 all four passes were completed and it was confirmed that the twaite shad had passed all of the passes, allowing the species to return to its natural spawning habitat.[7][8]
Referencesedit
^ abcFreyhof, J.; Kottelat, M. (2008). "Alosa fallax". IUCN Red List of Threatened Species. 2008: e.T904A174776207. doi:10.2305/IUCN.UK.2008.RLTS.T904A174776207.en. Retrieved 15 November 2021.
^"Allis shad: Alosa alosa". NatureGate. Retrieved 14 December 2013.
^ abcdefLochet, A., S. Boutry, and E. Rochard. Estuarine Phase during Seaward Migration for Allis Shad Alosa Alosa and Twaite Shad Alosa Fallax Future Spawners. Ecology of Freshwater Fish 18 (2009): 323-35.
^ abcdefghCoscia, I., V. Rountree, J. J. King, W. K. Roche, and S. Mariani. A Highly Permeable Species Boundary between Two Anadromous Fishes. Journal of Fish Biologydoi:10.1111/j.1095-8649.2010.02768.x 77.5 (2010): 1137-149.
^. jncc.defra.gov.uk. Archived from the original on 2011-07-04.
^"Rare fish set for return to River Severn breeding grounds". BBC News. 6 May 2021. Retrieved 6 May 2021.
^"Endangered twaite shad fish return to habitat unlocked after 180 years! - Unlocking the SevernUnlocking the Severn". 2022-07-15. Retrieved 2023-06-15.
^"Unlocking the Severn | Canal & River Trust". canalrivertrust.org.uk. Retrieved 2023-06-15.
External linksedit
Froese, Rainer; Pauly, Daniel (eds.) (2006). "Alosa fallax" in FishBase. April 2006 version.
January 01, 1970
twait, shad, twait, shad, twaite, shad, alosa, fallax, species, fish, family, alosidae, found, eastern, atlantic, ocean, mediterranean, anadromous, fish, which, lives, migrates, into, fresh, water, spawn, appearance, resembles, atlantic, herring, distinctive, . The twait shad or twaite shad Alosa fallax is a species of fish in the family Alosidae 1 It is found in the eastern Atlantic Ocean and the Mediterranean Sea and is an anadromous fish which lives in the sea but migrates into fresh water to spawn In appearance it resembles an Atlantic herring but has a row of six to ten distinctive spots on its silvery flanks They become mature when three or more years old and migrate to estuaries later swimming up rivers to spawn Populations of this fish have declined due to overfishing pollution and habitat destruction Conservation of this species is covered by Appendix III of the Bern Convention and Appendix II and V of the European Community Habitats Directive Twait shad Conservation status Least Concern IUCN 3 1 1 Scientific classification Domain Eukaryota Kingdom Animalia Phylum Chordata Class Actinopterygii Order Clupeiformes Family Alosidae Genus Alosa Species A fallax Binomial name Alosa fallaxLacepede 1800 Contents 1 Description 2 Distribution 3 Biology and lifecycle 4 Population reduction 5 Conservation 6 References 7 External linksDescription editThe twait shad is a typical herring type fish and much resembles the allis shad It has no lateral line and the belly is more rounded than that of the sprat and Baltic herring The gill cover is ridged and the caudal peduncle has large plate like scales This fish is more colourful than the Baltic herring The back is a bluish green colour and the head brownish with a golden tinge on the operculum The flanks are silvery sometimes with a bronzy tinge and there are a distinctive row of six to ten large dark spot just behind the gill cover though these may fade when the fish is dead The adult length is typically 25 to 40 cm 10 to 16 in 2 Distribution editThe twait shad is found in most of Europe and all countries bordering the Mediterranean Sea 1 Biology and lifecycle editAlosa fallax has a similar lifecycle to A alosa allis shad They are known to live in sympatry 3 Some studies have suggested A fallax and A alosa species can hybridize 4 They are anadromous species like many other species in the genus Alosa 4 However some record of them being landlocked suggests an ability to adapt well to their environment 4 They primarily live at sea on feeding grounds and migrate to their spawning grounds between April and June once they are sexually mature 4 Maturity usually ranges from 3 7 years of age 4 Juveniles appear in estuaries and brackish water around June to July 3 The salinity of brackish water may pose problems to the juveniles migrating from fresh water 3 Population reduction editPopulations have been reduced primarily through overfishing pollution habitat destruction and migratory route obstruction in the Victorian Era 5 4 Hybridization between species is more likely with species affected by human disturbances 4 It is estimated that the estuarine phase or the time that they are in the estuaries migrating from spawning grounds to sea has a duration in A fallax of up to a year and a half 3 The estimate however does not take into account individual variation and survival of juveniles in the estuarine phase 3 Conservation editFour special areas of conservation have been designated in Ireland where Alosa species have been known to spawn 4 Alosa fallax has been placed in Appendix III of the Bern Convention 1979 that lists protected fauna species as well as in appendix II and V of the European Community Habitats Directive 1992 that list respectively species whose conservation requires the designation of special areas of conservation and that are subject to management measures 3 In England the Unlocking The Severn project a consortium of the Canal amp River Trust Severn Rivers Trust Environment Agency and Natural England is creating fish passes around weirs on the River Severn The aim is to open 150 miles 241 km of the river for the fish to increase its freshwater breeding habitat By 2021 passes at Diglis and Bevere near Worcester had been completed 6 and by 2022 all four passes were completed and it was confirmed that the twaite shad had passed all of the passes allowing the species to return to its natural spawning habitat 7 8 References edit a b c Freyhof J Kottelat M 2008 Alosa fallax IUCN Red List of Threatened Species 2008 e T904A174776207 doi 10 2305 IUCN UK 2008 RLTS T904A174776207 en Retrieved 15 November 2021 Allis shad Alosa alosa NatureGate Retrieved 14 December 2013 a b c d e f Lochet A S Boutry and E Rochard Estuarine Phase during Seaward Migration for Allis Shad Alosa Alosa and Twaite Shad Alosa Fallax Future Spawners Ecology of Freshwater Fish 18 2009 323 35 a b c d e f g h Coscia I V Rountree J J King W K Roche and S Mariani A Highly Permeable Species Boundary between Two Anadromous Fishes Journal of Fish Biology doi 10 1111 j 1095 8649 2010 02768 x 77 5 2010 1137 149 1103 Twaite shad Alosa fallax SAC selection species account jncc defra gov uk Archived from the original on 2011 07 04 Rare fish set for return to River Severn breeding grounds BBC News 6 May 2021 Retrieved 6 May 2021 Endangered twaite shad fish return to habitat unlocked after 180 years Unlocking the SevernUnlocking the Severn 2022 07 15 Retrieved 2023 06 15 Unlocking the Severn Canal amp River Trust canalrivertrust org uk Retrieved 2023 06 15 External links editFroese Rainer Pauly Daniel eds 2006 Alosa fallax in FishBase April 2006 version Retrieved from https en wikipedia org w index php title Twait shad amp oldid 1222429033, wikipedia, wiki, book, books, library,
