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Author: Lacepède, 1803

Alosa fallax Lacepède, 1803

Diagnosis: body moderately deep, belly with a prominent keel of scutes, upper jaw with a distinct median notch. Gillrakers short and coarse, total 30-80 on first arch, about equal to gill filaments. Colour: back brilliant blue, flanks silvery to white, with a dark spot posterior to gillopening and a series of 5-6 others after this. Size: to 50 cm, usually 20-40 cm.

Habitat: marine pelagic, also penetrating a short distance up rivers (but some purely freshwater populations in lakes); shoaling, strongly migratory. Food: small fishes, euphausiids, mysids and isopods. Reproduction: mostly anadromous, entering river mouths in March (Italy) or early June (northern European rivers) to spawn in or above the tidal reaches; eggs demersal and widely scattered among sand or gravel on river bed; adults probably return to sea not long after spawning.

Distribution: Atlantic coasts from northern Morocco to southern and western Iceland and Bergen; North Sea, Baltic, Gulf of Bothnia and Gulf of Finland; also Mediterranean.

Eggs, larvae and young stages. No data.
Otoliths (sagitta). No data.

Subspecies

Alosa fallax fallax Lacèpede, 1803
A. fallax fallax: total gillrakers 37-42; Atlantic coasts (?including the goureen A. fallax killarnensis of Killarney lakes, Ireland, but gillrakers 43-53; a separate subspecies by some authors) (Clofnam 33.6.3.1).
Eggs, larvae and young stages. Ehrenbaum, 1896: 56, pl. II (fig. 9-15) | Hass, 1969: 23.
Otoliths (sagitta). Jenkins, 1902: 116, pl. III (fig. 15-16) | Frost, 1925: 154, pl. XI (fig. 10) | Chaine, 1938b: 175, pl. XIII | Bauzá-Rullán, 1958b: 124, pl. II (fig. 11-15).

Alosa fallax nilotica Geoffroy Saint-Hilaire, 1808
A. fallax nilotica: total gillrakers 34-37; Mediterranean, Adriatic (common), Marmara and Black Seas (rare) (?including A. fallax lacustris of Italian lakes, gillrakers to 76; separate subspecies by some authors) (Clofnam 33.6.3.2).
Eggs, larvae and young stages. Hoestlandt, 1947: 938.
Otoliths (sagitta). Jenkins, 1902: 116, pl. III (fig. 15-16) | Frost, 1925: 154, pl. XI (fig. 10) | Chaine, 1938: 175, pl. XIII | Bauzá-Rullán, 1958: 124, pl. II (fig. 11-15).

Twaite shad (Alosa fallax)