Rudderfish

The rudderfish is a sturdy, dark medusafish of the open ocean, the only species in its genus, which ranges from near the surface to more than 1000m down and eats almost anything of the right size, from small fish to drifting medusae.

It lives singly or in small schools over deep oceanic water. In the Atlantic it occurs on both sides, from Nova Scotia to Massachusetts in the west and into the Mediterranean in the east, and it turns up again off South Africa, Australia, New Zealand and in the Southern Ocean. It is largely missing from the tropics, but appears occasionally around the British Isles, with records off County Galway, County Donegal and the Isles of Scilly.

Appearance

The body is spindle-shaped, with a grey head and a violet-black, dark brown or purplish body that pales on the belly. Its fins are darker still, and some fish show faint spots or a marbled pattern. Most reach about 60cm, though the biggest grow to two and a half times that.

Feeding

It is not a fussy eater and takes whatever suitably sized prey is around, including small fish, squid, copepods and amphipods, as well as medusae and comb jellies.

Life cycle

Juveniles are believed to stay in surface waters, often with drifting medusas and salps, while adults live deeper and may gather in small schools.