| Twait shad | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Clupeiformes |
| Family: | Clupeidae |
| Subfamily: | Alosinae |
| Genus: | Alosa |
| Species: | A. fallax |
| Binomial name | |
| Alosa fallax Lacépède, 1800 |
|
The twait shad or twaite shad (Alosa fallax) is a species of fish in the Clupeidae family.[1]
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It is found in most of Europe and all countries bordering the Mediterranean Sea.[1]
Alosa fallax has a similar lifecycle to Alosa alosa (allis shad). They are known to live in sympatry with Alosa alosa. [2] Some studies have suggested that the Alosa fallax and Alosa alosa species can hybridize.[3] They are anadromous species just like many other species in the Alosa genus.[3] However, there is some record of them being landlocked suggesting an ability to adapt well to their environment. [3] They primarily live at sea on feeding grounds and will migrate to their spawning grounds between April and June once they are sexually mature.[3] Maturity usually ranges from 3-7 years of age.[3] It is observed that juvenilles appear in estruaries, brackish water, around June to July.[2] The salinity of brackish water may impose problems to the juveniles migrating from freshwater.[2]
Populations have been reduced primarily through overfishing, pollution, and habitat destruction.[3] Hybridization between species is more likely with species affected by human disturbances.[3] It is estimated that the estruarine phase, or the time that they are in the estruaries migrating from spawning grounds to sea, has a duration in Alosa fallax of up to a year and a half.[2] The estimate however does not take into account individual variation and/or survival of juveniles in the estruarine phase.[2]
Four special areas of conservation have been designated in Ireland where Alosa species have been known to spawn.[3] 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.” [2]