Fish vs Structure vs Weeds: How to Read Your Sonar Like a Pro

SECTION: IDENTIFYING FISH

Fish usually appear as arches or small blobs on 2D / CHIRP sonar. On Side Imaging, fish may appear as small suspended targets casting shadows on the bottom.

Tips for beginners:

• Fish arches are curved marks moving across the screen

• Suspended fish appear off the bottom in Side Imaging

• Observe the size, movement, and density to distinguish schools from individual fish

• How to read sonar = for detailed sonar reading

2D CHIRP sonar showing clear fish arches with beginner settings

SECTION: RECOGNIZING WEEDS & VEGETATION

Weeds and vegetation are one of the most misread elements on sonar. Key characteristics:

• Fuzzy, tall vertical marks rising from the bottom

• Often connected to the bottom

• Can create a wall or canopy

• Do not form arches like fish

Pro tip: Use Side Imaging to see the shape of weed edges — fish often hang just outside weed beds.

Weed bed appearing as fuzzy vertical marks on Side Imaging sonar (right) and 2D (left)

SECTION: UNDERSTANDING STRUCTURE

Down Imaging is excellent for seeing fish directly under the boat. Beginner tips:

• Frequency: Usually 800 kHz for shallow water, 455 kHz for deeper water

• Range: Auto mode works, adjust if fish are missed

• Contrast: Slightly higher than side imaging to see details

• Boat Speed: Slow to moderate for jigging or tight spots

Links:

• Down imaging → full Down Imaging tutorial

Various Structures

Structures on Side Imaging Sonar (left)

• Hard objects like rocks, brush piles, or submerged trees reflect strong signals show up bright on screen.

Structures on Down Imaging Sonar (right)

• Can see fine details of objects like branches, rocks, and drop-offs.

SECTION: COMMON MISTAKES

Many anglers confuse fish, weeds, and structure. Avoid these mistakes:

• Chasing every arch you see → not all are fish

• Assuming all fuzzy marks are weeds → some may be baitfish

• Ignoring shadows → they reveal size and position of fish and structure

• Wrong sonar settings → can hide fish or exaggerate weeds

SECTION: SIDE IMAGING & DOWN IMAGING TIPS

• Side Imaging: Great for identifying fish along weed edges and structure. Look for shadows to confirm targets.

• Down Imaging: Helps spot fish directly under the boat in dense vegetation.

• 2D CHIRP: Confirms size and depth of fish.

Walleye on Side Imaging

• Bright, elongated shape slightly above the bottom.

• Often accompanied by a dark shadow behind it, which helps indicate how far it is from the bottom.

Stop guessing and start catching more fish. Book hands-on sonar training or a guided trip and learn how to read fish vs structure vs weeds in real conditions.