The twait shad or twaite shad (Alosa fallax) is a species of fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 in the Clupeidae

Clupeidae

Clupeidae is the family of the herrings, shads, sardines, hilsa and menhadens. It includes many of the most important food fishes in the world.-Description and biology:...

 family.

Location

It is found in Albania

Albania

Albania , officially known as the Republic of Albania , is a country in Southeastern Europe, in the Balkans region. It is bordered by Montenegro to the northwest, Kosovo to the northeast, the Republic of Macedonia to the east and Greece to the south and southeast. It has a coast on the Adriatic Sea...

, Algeria

Algeria

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, Austria

Austria

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, Belgium

Belgium

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, Bulgaria

Bulgaria

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, Croatia

Croatia

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, Cyprus

Cyprus

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, Denmark

Denmark

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, Egypt

Egypt

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, Estonia

Estonia

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, Finland

Finland

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, France

France

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, Germany

Germany

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, Gibraltar

Gibraltar

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, Greece

Greece

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, Ireland

Ireland

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, Israel

Israel

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, Italy

Italy

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, Latvia

Latvia

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, Lebanon

Lebanon

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, Lithuania

Lithuania

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, Malta

Malta

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, Morocco

Morocco

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, the Netherlands

Netherlands

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, Norway

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, Poland

Poland

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, Portugal

Portugal

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, Russia

Russia

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, Serbia and Montenegro

Serbia and Montenegro

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, Spain

Spain

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, Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

, Switzerland

Switzerland

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, Syria

Syria

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, Tunisia

Tunisia

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, Turkey

Turkey

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, and the United Kingdom

United Kingdom

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.

Biology and Life-cycle

Alosa fallax has a similar lifecycle to Alosa alosa (allis shad). They are known to live in sympatry with Alosa alosa. Some studies have suggested that the Alosa fallax and Alosa alosa species can hybridize. They are anadromous species just like many other species in the Alosa genus. However, there is some record of them being landlocked suggesting an ability to adapt well to their environment.
They primarily live at sea on feeding grounds and will migrate to their spawning grounds between April and June once they are sexually mature. Maturity usually ranges from 3-7 years of age. It is observed that juvenilles appear in estruaries, brackish water, around June to July. The salinity of brackish water may impose problems to the juveniles migrating from freshwater.

Population Reduction

Populations have been reduced primarily through overfishing, pollution, and habitat destruction. Hybridization between species is more likely with species affected by human disturbances. 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. The estimate however does not take into account individual variation and/or survival of juveniles in the estruarine phase.

Conservation

Four special areas of conservation have been designated in Ireland where Alosa species have been known to spawn. 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.”