Fish
Ruffe
Gymnocephalus cernua · also called pope
On the muddy bottom of a lake at dusk, a ruffe lies motionless, the sensory pits on its head tuned to the faint vibrations of a passing insect larva.
Overview
The ruffe, Gymnocephalus cernua, is a Least Concern perch relative of lakes, slow rivers, and brackish waters across Europe and northern Asia, and an invader in the Great Lakes of North America. Its spiny fin, head pits, and spread across the Atlantic make it a small fish with a big reputation.
A small fish that travelled
Carried in ballast water to the Great Lakes, the ruffe spread rapidly and competes with native fish, which is why it is watched closely by fisheries managers.
Status
Least Concern, abundant in its native range and invasive in the Great Lakes.
Ruffe: common questions
How is a ruffe different from a perch?
It has a single, continuous, spiny dorsal fin, unlike the two separate fins of a perch, and is smaller and more speckled.
Why is the ruffe a problem in North America?
It reached the Great Lakes in the 1980s, probably in ships' ballast water, and spread widely there.
How does the ruffe hunt in the dark?
It has large, sensory pits on its head, which detect vibrations in the water.
Where is the ruffe found?
It lives in lakes, slow rivers, and brackish waters across Europe and northern Asia, and in the Great Lakes of North America.