Reading the Bottom – Substrate, Depth & Structure
What lies beneath the surface matters more than what’s happening on top.
Carp don’t roam randomly. They follow food, comfort, and underwater highways. If you understand bottom type, depth changes, and structure, you can predict where carp will feed before ever casting a line.
The Major Bottom Types
Silt (Soft Organic Sediment)
Dark, soft bottom rich in bloodworm.
Carp love silt and root through it feeding.
• Extremely food-rich
• Leads sink easily
• Bottom baits can disappear
Use lighter leads and pop-ups or wafters.
Common in protected bays and coves.
Sand
Clean, firm bottom with lower food content.
Excellent presentation.
• Bottom baits sit clean
• Easier hook-ups
• Often near beaches
Target transitions where sand meets silt or weed.
Gravel
Small stones with moderate invertebrate life.
Crayfish common.
• Fantastic rig presentation
• Abrasive on leaders
Use fluorocarbon 20lb+.
Often found in current areas and lake points.
Rock & Boulder
High risk, high reward.
Crayfish and mussels attract big carp.
• Extreme snag potential
• Accept tackle loss
Use heavy leaders (25lb+).
Common along Lake Michigan shorelines.
Weed
Summer feeding factories.
Loaded with shrimp, snails, and insect larvae.
• Bottom baits vanish
• Fish edges and gaps
• Pop-ups essential
Apply immediate pressure on hookup.
The Lead Test (Old-School Bottom Reading)
Cast out.
Let lead hit bottom.
Slowly drag.
Feel:
Soft = silt
Smooth = sand
Crunchy = gravel
Jerky = rock
Spongy resistance = weed
This works everywhere.
Depth & Carp Positioning
Shallow (0–6 ft)
Dawn, dusk, spawning, warm evenings
Medium (6–15 ft)
Most consistent feeding depth
Deep (15–30 ft)
Summer refuge and winter holding
Carp move vertically constantly.
Depth changes matter more than absolute depth.
Structure – Underwater Highways
Carp follow structure like roads.
Look for:
• Points
• Humps
• Drop-offs
• Holes
• Channels
Best areas combine structure + food.
Example: silt bay with drop-off = carp magnet.
Michigan Notes
River mouths combine depth change, current, and food.
Inland lakes often have subtle humps holding fish all season.
Wind-blown points regularly outfish flat banks.
Key Takeaways
• Silt = food
• Sand = presentation
• Gravel = quality fish
• Weed = summer magnets
• Medium depths most productive
• Structure concentrates carp
• Learn the lead test
• Find transitions
Read the bottom, find the carp.
Next Steps
Continue with:
Watercraft & Conditions → Article 9: Weed Beds, Lily Pads & Aquatic Vegetation
https://michigancarp.com/watercraft/