(Steenstrup, 1882)
Description
Adult. A small nektonic squid with a thin, narrow, weakly muscular, cylindrical mantle. Head is small and narrow. Fins transversely rhomboidal or widely heart-shaped, not attenuated or just slightly attenuated posteriorly. Arms with two rows of suckers. There are many rows of small suckers in the proximal part of the tentacular club, the distal part with 4-6 rows of initially large and then gradually smaller suckers. Mantle length up to 10-17 cm. Fin length 35-50 % of the mantle length. Mantle is nearly colourless, with scarce small chromatophores.
Larvae/juvenile [Bracioteuthis sp-y ]. Specific description incomplete. Larvae have a long neck; distinctive surfal swalling of the head. Tentacles large, robust relative to the arms and already present at hatching. Club suckers with adult-like pattern of numerous suckers on proximal manus well established by mantle length of about 10 mm. Fins separated, terminal, paddle-shaped and transversely oval. Smallest known larvae show a mantle length of about 3 mm. [After Roper and Sweeney, in Sweeney et al., 1992].
Size
Maximum mantle length about 17 cm.
Depth range
Common from 0-100 m, down to 300 m depth (though catches from 2000-3000 m have been reported); juveniles in 0-200 m. B. riisei is suspected to undertake diurnal vertical migration.
Distribution in the North Sea
Northern North Sea, Skagerrak.
World distribution
Probably a cosmopolitan species between 60°N and 60°S, except for boreal Pacific.