[4][5][6] The smallmouth spiny eel is silver or brown in colour, with a maximum length of 36 cm (14 in).

It looks similar to Polyacanthonotus africanus but its lateral line is lighter and less distinct.

[7] The smallmouth spiny eel lives in the Arctic waters off of Canada and in the North Atlantic Ocean off of Iceland, Ireland and Great Britain; it has also been observed in the waters off South Africa and in the Tasman Sea.

[8][9] It is a benthic and bathydemersal species, living at depths of 500–2,800 m (1,600–9,200 ft).

[10][11][12] Polyacanthonotus rissoanus feeds on coelenterates, worms and crustaceans.