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Grass Carp

Grass Carp

Grass Carp in Illinois are large, non-native fish considered common and present throughout the state's waterways as part of ongoing invasive species management efforts.

Scientific Name: Ctenopharyngodon idella

Physical Characteristics:
  • Large fish with distinctive olive-brown coloration, large overlapping scales with dark edges, and an oblong body shape with a slightly flattened head.
  • These powerful fish can reach over 80 pounds and 49 inches in length.

What to know

Habitat Distribution

  • Widely distributed throughout Illinois waters.
  • They prefer large, slow-flowing water bodies.

Key Locations

  • Illinois Waterway, Chicago Area Waterway System, backwaters of lakes, ponds, slower rivers and creeks, and canals statewide.

Specific Spots

  • Focus on backwaters of lakes, ponds, slower rivers and creeks, and canals throughout Illinois where grass carp cruise like submarines in relatively deeper water.
  • Target areas with emergent vegetation, cattail edges, and shoreline plants where cottonwood seeds or insects are present on the surface.

Grass Carp FAQ

Answers from onWater's species guide.

What flies work for Grass Carp in Illinois?

Effective fly patterns include size 12-16 beadhead woolly buggers, beadhead hares ear nymphs (#14-18), CDC caddis (#12-14), cottonseed patterns (#12-16), and parachute hoppers (#12-16). Many flies should imitate plant material or insects present on the surface.

When is the best time to fish for Grass Carp in Illinois?

March through November when water temperatures are 50-75°F, avoid fishing during active spawning periods from late spring into summer (May-July) when water temperatures reach 64-77°F.

How do you catch Grass Carp in Illinois?

Cast 10-15 feet ahead of cruising fish to the right or left of their path (they have a blind spot directly in front). Present flies delicately with low, tight loops at 40-60 feet distances. Don't cast over their heads or make the fly move aggressively as they're more likely to flee than chase moving flies.

What do Grass Carp eat?

Primarily herbivorous, feeding on aquatic plants but also consuming detritus, insects, small fish, earthworms and invertebrates when vegetation is scarce. They can consume 20-100% of their body weight daily depending on water temperature, life stage, and available vegetation.

Where do Grass Carp live in Illinois?

Widely distributed throughout Illinois waters. They prefer large, slow-flowing water bodies.

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