10 20 40 60 cm
mittakaava < 40 cm
© Copyright: Images:
www.scandfish.com, Lauri Urho. All rights reserved.
- Other names: Twait shad
- Family: Herrings – Clupeidae
- Similar species: allis shad, baltic herring (giant form)
- Size: 25–40 cm, may exceed 1 kg.
- Appearance: The twaite shad is a slightly smaller fish than its close relative the allis shad. Both are encountered only occasionally along Finland’s coasts. A typical herring fish in shape, the twaite shad is generally larger than the sprat and Baltic herring, so that the only species with which it might possibly be confused are the giant Baltic herring and the allis shad. The lateral line is absent, the belly more rounded than either Baltic herring or sprat. Ridges on gill cover, caudal peduncle has large, plate-like scales. Eye covered by a nictating membrane. Also differs from the giant Baltic herring by its deeper body. Distinguished from the allis shad by the number of gill rakers on the first gill arch: over 60 (usually 80-130) for the allis shad and usually fewer than 60 for the twaite shad.
- Colouring: Back bluish green, head brown, some gold colour on operculum. Sides generally silvery, sometimes with a golden tinge. Exhibits more colour than the Baltic herring. Characteristic are the 6–10 dark spots along the back, though these may fade after the fish is killed.
- Reproduction: Ascends rivers to spawn. Not known to spawn in Finland.
- Food: Plankton.
- Distribution and habitat: The twaite shad is an occasional visitor to Finnish waters, the most recent recording being off Merikarvia near Pori in 2003.