Side-scan Sonar Basics

Side-scan sonar shoots off to the port and starboard side of your boat, and marks fish and structure. Side-scan works very well in conjunction with regular sonar, which shoots directly beneath your boat.

It is difficult to mark fish with side-scan when traveling at speeds which create a lot of bubbles and disturbance from the engine. 

For example, I have had my best success marking fish using side-scan when traveling at trolling speed, however I can also mark fish when traveling at 10mph, because the pitch of my boat offers the side-scan sonar beams a clear shot with no bubbles or disturbance from the engine.

Engine disturbance on my boat becomes too great at speeds higher than 10 mph, and due to the pitch of my boat, side-scan doesn't work well for me when traveling between 3-8mph. The moral of the story is that trolling speed generally works well on all boats, but you'll have to experiment with how your boat and side-scan work when traveling at higher clips.

What Do Fish Look Like On Side-Scan?

Fish will appear as white lines on side scan. Schools of fish will appear as many individual white lines. In many instances the size of the white lines does indicate the size of the fish.

For example, short white lines are often schoolies or bluefish, while big white lines are 25 plus pound stripers.

You can often even count the amount of fish in a school by counting the white lines.

Also, in some situations you may just catch sight of the side-scan sonar “shadow” and not the white line. Yet the shadow also indicates that a fish was marked, so keep your eyes open for both the white lines and any shadows.

Best & Worst Situations For Sidescan Sonar

In my opinion, side-scan works best in deep water during calm conditions. I get super clear and clean markings in this type of situation.

Side-scan also works well in shallow water areas when it is calm. I can mark fish, as well as weed beds, rocks, boulders and other structure using side-scan sonar in shallow during calm conditions.

Side-scan does not work very well for me in rough conditions. My boat pitches up and down in rough conditions, which causes bubbles and disturbs the side-scan sonar readings. There’s often so much clutter and noise on the side scan that I will not even use it when it’s rough.

I have also not received much benefit from using side-scan in areas where the bottom undulates greatly. In one particular spot I often fish, bass settle down into the troughs of large underwater “sand dunes”.

The side-scan is useless here because the sonar beams bounce off the crests of the underwater “sand dunes” and just can’t get to the bass which are holding in the troughs.

In this situation the regular sonar is all I use.

Using Sidescan To Catch
More Fish

So how exactly can you utilize side-scan sonar to put a few more nice fish in your boat?

Here’s two specific ways side scan can help:

1) Side scan will mark fish holding shallow, which you would miss using just your regular sonar.

Because your regular sonar shoots directly beneath your boat in a cone shape, you will rarely mark many fish that are holding shallower than 15 feet beneath the surface. The cone shape of the regular sonar beam simply does not allow it.

Yet with side-scan sonar you can mark fish that are holding just beneath the surface, and even fish that are working right on the surface. Big bass will sometimes focus on the upper portion of the water column, and without side scan you could miss out on these fish.

2) Side scan shows you what side of the boat most of the fish are on.

With regular sonar you may mark a big school of fish beneath your boat. Well, at least it appears as if that big school of fish is directly beneath your boat.

Truth is that the school may be slightly off to the port or starboard. With side scan you will see exactly what side of the boat the majority of the fish are holding on.

If you’re casting plugs or bait this can be useful, because you’ll know what side of the boat is best to cast at.

You may also pick up on the general direction that the school is moving. If you are drifting through a school of fish you may see that the school is first on your port, then passes beneath the boat, and then disappears to the starboard.

Now you at least know the general direction the fish are moving.

In Conclusion

I feel that side-scan is worth the extra money, especially right now because the price has come way down, compared to how much side scan cost 10 years ago.

What specific questions do you have with regards to side scan sonar? Let me know by commenting below.

Tight lines!