Twait shad
| Twait shad | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Clupeiformes |
| Family: | Clupeidae |
| Subfamily: | Alosinae |
| Genus: | Alosa |
| Species: | A. fallax |
| Binomial name | |
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Alosa fallax Lacépède, 1800 |
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The twait shad or twaite shad (Alosa fallax) is a species of fish in the Clupeidae family. 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).
The twait shad is found in most of Europe and all countries bordering the Mediterranean Sea.
Alosa fallax has a similar lifecycle to A. alosa (allis shad). They are known to live in sympatry. Some studies have suggested A. fallax and A. alosa species can hybridize. They are anadromous species, like many other species in the Alosa genus. 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. Juveniles appear in estuaries and brackish water around June to July. The salinity of brackish water may pose problems to the juveniles migrating from fresh water.
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Wikipedia