A dark, deep-bodied jack of steep outer walls and offshore rock, often in small groups above the drop.
To about a metre. The only uniformly dark jack in these waters: body and fins grey to black, the scutes along the tail base jet black, and a small dark spot at the upper corner of the gill opening. The head profile is steep and angular with a distinct dip between the snout and the nape.
The bluefin trevally is the fish to rule out, and it is blue-spotted with electric-blue fins, never black-finned.
Twelve to over three hundred metres, in deep clear water around oceanic islands, on reef drop-offs and over seamounts. It is not a shallow-bank fish, which is why Roca Partida and the offshore rock suit it. Solitary or in schools of up to about thirty, hunting fish at night.
One documented oddity: it has been recorded following spinner dolphins and feeding on their excrement.
Numerous ciguatera cases are confirmed for this species and the toxin has been verified in its flesh.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.