# Allis shad > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Allis_shad > Markdown URL: https://mediated.wiki/source/Allis_shad.md > Source: https://en.wikipedia.org/wiki/Allis_shad > Source revision: 1322911636 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Species of fish}} {{Speciesbox | name = Allis shad | image = Alosa alosa.jpg | status = CR | status_system = IUCN3.1 | status_ref ={{cite iucn |author=Ford, M. |year=2024 |title=''Alosa alosa'' |article-number=e.T903A15541267 |doi=10.2305/IUCN.UK.2024-2.RLTS.T903A15541267.en}} | genus = Alosa | species = alosa | authority = ([Linnaeus](/source/Carl_Linnaeus), [1758](/source/10th_edition_of_Systema_Naturae)) |synonyms=*''Alausa vulgaris'' Valenciennes, 1847 *''Alosa communis'' Yarrell, 1836 *''Alosa cuvierii'' Malm, 1877 *''Alosa rusa'' Mauduyt, 1848 *''Clupea alosa'' Linnaeus, 1758 |synonyms_ref={{GBIF|taxon=''Alosa alosa'' (Linnaeus, 1758)|id=2412685|access-date=29 October 2024}}{{FishBase|Alosa|alosa|month=October|year=2024}} }} thumb|Allis shad The '''allis shad''' ('''''Alosa alosa''''') is a widespread Northeast Atlantic species of [fish](/source/fish) in the [Alosidae family](/source/Alosidae). It is an [anadromous](/source/Fish_migration) fish which migrates into fresh water to spawn. It is found in the eastern Atlantic Ocean, the western Baltic Sea and the western Mediterranean Sea. In appearance it resembles an [Atlantic herring](/source/Atlantic_herring) but has a distinctive dark spot behind the gill cover and sometimes a row of up to six spots behind this. It sometimes [hybrid](/source/Hybrid_(biology))ises with the [twait shad](/source/twait_shad) (''A. fallax''). This fish becomes mature when three or more years old and migrates to estuaries, later swimming up rivers to spawn. Populations of this fish have declined due to [overfishing](/source/overfishing), pollution and [habitat destruction](/source/habitat_destruction). Conservation of this species is covered by Appendix III of the [Bern Convention](/source/Berne_Convention_on_the_Conservation_of_European_Wildlife_and_Natural_Habitats) and Appendix II and V of the [European Community Habitats Directive](/source/Habitats_Directive). ==Description== The allis shad is a typical herring-type fish. It has no [lateral line](/source/lateral_line) and a somewhat rounded belly. The [gill cover](/source/gill_cover) is ridged and the [scales](/source/Fish_scale) large. The back is a bluish-green colour and the head brownish with a golden tinge on the [operculum](/source/Operculum_(fish)). The flanks are silvery, sometimes with a bronzy tinge, and a distinctive large dark spot occurs just behind the gill cover, and occasionally one to six smaller spots behind that. The adult length is typically {{convert|30|to|60|cm|abbr=on}}.{{cite web |url=http://www.luontoportti.com/suomi/en/kalat/allis-shad |title=Allis shad: ''Alosa alosa'' |publisher=NatureGate |access-date=14 December 2013}} ==Distribution== The allis shad is found in the eastern Atlantic in waters bordering most of [Europe](/source/Europe) and northwestern [Africa](/source/Africa), and it enters to the western [Baltic](/source/Baltic_Sea) and western [Mediterranean](/source/Mediterranean) Seas, but it is rare outside and increasingly within [France](/source/France). There are no longer breeding populations in Morocco or Mediterranean Spain. ==Biology and lifecycle== thumb|left|Biology and lifecycle of ''Alosa alosa''. ''Alosa alosa'' has a similar lifecycle to that of the [twait shad](/source/twait_shad) ''A. fallax''. They are known to live in [sympatry](/source/sympatry),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. and the two species can hybridize. They are [anadromous](/source/anadromous) species like many other species in the genus ''Alosa''.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. However, some record of them being landlocked suggests an ability to adapt well to their environment. They primarily live at sea on feeding grounds and migrate to their spawning grounds between April and June once they are sexually mature. Maturity usually ranges from 3–7 years of age. ''A. alosa'' can usually only reproduce once in their lifetimes. Juveniles appear in [estuaries](/source/estuaries) and brackish water around July to August. The salinity of brackish water may pose problems to the juveniles migrating from fresh water. The estuarine phase, or the time spent in estuaries migrating from spawning grounds to sea, is estimated to have a duration in ''A. alosa'' of up to six months. The estimate, however, does not take into account individual variation and/or survival of juveniles in the estuarine phase. ==Population reduction== Populations have been reduced primarily by [overfishing](/source/shad_fishing), pollution, and habitat destruction. [Siltation](/source/Siltation) and [gravel](/source/gravel) mining threaten spawning locations. There is concern that barriers to migration like dams are causing allis shad to spawn downstream from their usual locations, potentially prompting hybridization with twaite shad. Climate change may force the species' distribution to shift or contract further. The [International Union for Conservation of Nature](/source/International_Union_for_Conservation_of_Nature) listed the species as [critically endangered](/source/critically_endangered) in 2024, citing an estimated global population decline of around 80% over the past 20 years, leaving many small relict subpopulations and [extirpating](/source/extirpating) others. ==Conservation== Four special areas of conservation have been designated in Ireland where ''Alosa'' species have been known to spawn. ''Alosa alosa'' "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." However, ''A. alosa'' is currently under a moratorium (2008) in numerous French watersheds. ==References== {{Reflist}} ==External links== * [http://www.alosa-alosa.eu EU LIFE-Project: The re-introduction of allis shad (''Alosa alosa'') in the Rhine system] * {{Cite NIE|wstitle=Allice|year=1905 |short=x}} {{Taxonbar|from=Q300997}} {{Authority control}} Category:Alosa Category:Fauna of France Category:Marine fish of Europe Category:Fish described in 1758 Category:Animal taxa named by Carl Linnaeus Category:Least concern biota of Europe Category:Taxonomy articles created by Polbot Category:Habitats Directive species --- Adapted from the Wikipedia article [Allis shad](https://en.wikipedia.org/wiki/Allis_shad) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Allis_shad?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.