Sio nordenskjoldii

Common Name

Nordenskjold's Bigscale

Year Described

Lönnberg, 1905


Dorsal Fin: III, 9
Anal Fin: I, 8-9
Pectoral Fin: 13-15
Pelvic Fin: I, 7
Caudal Fin: 9-11 branched, 3-5 procurrent rays
Lateral Scale Rows: 29-35
Gill Rakers: 24-29
Vertebrae: 27-28

Head with numerous bony ridges and pits. No post-temporal spines, projecting anterior spines, or raised bony crest on top of head. Preopercle and upper opercular margins with serrations. Gill rakers in first arch relatively numerous (20 or more). Anal fin origin under last few dorsal rays. Pectoral fin reaches last ray of dorsal fin. Pelvic fin origin slightly behind pectoral fin origin. Body scales large and easily shed.


Uniformly brown to black


Maximum size to 108mm SL


Mesopelagic from 200-3000m. Adults are found more frequently in colder Antarctic waters while juveniles and larvae are collected into the subtropical boundary currents.


Circumpolar: found mostly south of the Southern Subtropical Convergence off Uruguay and Argentina. Juveniles are most likely to be caught further north and adults are far more commonly caught south of the South Polar Front around Antarctica and the Scotia Arc.


Kotlyar, A. N. 2002. Sio nordenskjoldii (Melamphaeidae): morphology and distribution. Journal of Ichthyology v. 42 (no. 1): 28-36.

Other Notes

Sio kreffti (Keene, 1987), an unpublished species from the southern ocean, is of uncertain status.