Darwin's Roughy

Gephyroberyx darwinii, the big roughy or Darwin's slimehead, is a species of fish in the slimehead family found widely in the Atlantic and Indo-Pacific oceans. This deep-sea species reaches a length of 60 cm (2.0 ft) and is mainly found at depths of 200 to 500 m (660–1,640 ft), but has been recorded between 9 and 1,210 m (30–3,970 ft). Based on broadly overlapping morphological features it sometimes (e.g., by IUCN) includes G. japonicus as a synonym.

Typical of Trachichthyidae, G. darwinii are laterally compressed, with a deep body, and have mucous-filled cavities within their heads. They possess large mouths with teeth on the vomer and palatine, large spines on their opercular bones, a ventral keel bearing robust scutes, and a forked tail. The species tends to be reddish in color. The species can be distinguished from sympatric Hoplostethus species by the presence of eight spines on the first dorsal fin (with the 3rd and 4th being the longest, spines on the lateral line scales, the opercular spine extending beyond the opercular's rear edge, a concave area between the eyes, and a comparatively small eye diameter.