Ruffe
Eurasian Ruffe is an invasive small perch-family fish that arrived in the Great Lakes through ship ballast water in the 1980s. In Canada, it's established near Thunder Bay on the Kaministiquia River and has been confirmed near Sault Ste. Marie.
It's not a target species — anglers encounter it as bycatch and are legally required to report or destroy it, not release it.
Scientific Name: Gymnocephalus cernua
Also known as Eurasian Ruffe, grémille eurasienne, blacktail, pope, river ruffe
- Olive-brown to golden-brown back with yellowish-white belly; irregular dark blotches along the flanks that can resemble a sauger or young walleye at a glance.
- Single fused dorsal fin with 12–19 hard spines followed by 11–16 soft rays — the spiny-to-soft fusion distinguishes it from perch, sauger, and walleye, which have a gap between their two dorsal fins.
- Typically 5–6 inches (12 cm); rarely exceeds 10 inches (25 cm). Most fish caught in Canadian waters are small enough to fit in a hand.
What to know
Habitat Distribution
- Introduced, not native — arrived in Lake Superior via ballast water discharge, likely in the early-to-mid 1980s. Now established in Ontario waters.
- Confirmed in the Kaministiquia River near Thunder Bay and recently detected near Sault Ste. Marie; suspected to be spreading east along Lake Superior's northern shore.
- Prefers lakes and slow or still rivers with soft bottoms and little vegetation; tolerates both fresh and slightly brackish water across a wide range of depths and nutrient levels.
Key Locations
- Kaministiquia River, Thunder Bay, Ontario — the primary confirmed Canadian location, connected to western Lake Superior.
- Sault Ste. Marie area, Ontario — recently confirmed, indicating eastward spread along Lake Superior's northern shore.
Specific Spots
- Soft-bottom areas in harbours, river mouths, and nearshore lake zones — ruffe hug the bottom and avoid open, well-lit water.
- Low-light zones near docks, pilings, and deeper nearshore structure; most active at dusk, night, and on overcast days.
- Slow backwater sections of rivers connected to Lake Superior, particularly where fine sediment accumulates and invertebrates are abundant.
Ruffe FAQ
Answers from onWater's species guide.
What are the best lures and bait for Ruffe?
Small jigs tipped with worm or maggot, or plain hook-and-worm rigs fished on the bottom, the same setups used for perch will catch ruffe incidentally in areas where they're present.
When is the best time to fish for Ruffe?
Can be encountered year-round in established areas, but most active in low-light conditions, dusk, night, and overcast days across all seasons. Spawning activity peaks in spring when water temperatures climb above 43°F (6°C), typically April through June in Ontario.
How do you catch Ruffe?
Ruffe are not deliberately targeted by anglers in Canada. They turn up as bycatch when fishing soft-bottom nearshore areas near Thunder Bay or Sault Ste. Marie with bottom rigs intended for perch or other species. Any ruffe caught should be reported to Ontario's Invading Species Hotline and not returned to the water.
What do Ruffe eat?
Bottom-dwelling invertebrates make up the bulk of the diet, insect larvae, copepods, and other small aquatic invertebrates. This overlaps heavily with yellow perch and other native species, which is why ruffe cause competitive harm in Canadian waters.
Where do Ruffe live?
Introduced, not native, arrived in Lake Superior via ballast water discharge, likely in the early-to-mid 1980s. Now established in Ontario waters. Confirmed in the Kaministiquia River near Thunder Bay and recently detected near Sault Ste. Marie; suspected to be spreading east along Lake Superior's northern shore.
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