Buying guide for Best fish finders
A fish finder makes a great addition to any fisherman’s tackle box. This technology can help you figure out if you’re in the right area on the water. It can show you lake maps and allow you to mark your favorite “hot spots.”
What’s more, fish finder technology continues to improve – even as the cost of these helpful gadgets continues to drop.
In short, now is the perfect time to consider purchasing a new fish finder.
At BestReviews, our top priority is to give our readers the information they need to make smart shopping decisions. We closely examine the products we endorse for quality, durability, and other key features. We’re confident that each of the fish finders in our product list gives a strong performance.
Types of fish finders
A fish finder uses sonar to scan an underwater area for objects. The sonar data creates a representation of the underwater area on a display screen. It can find the bottom of the lake, underwater plants where you could snag your line, and, of course, fish.
Because so many different fish finders are available, you can surely find one to meet your needs for the way you enjoy fishing. But first, it helps to understand a bit about the two major fish finder types: fixed and portable.
Fixed fish finders
A fixed fish finder attaches permanently to a boat.
Some fixed units screw permanently into the edge of the boat.
Others affix permanently to the bottom of the boat, sending sonar through the hull.
Portable fish finders
A portable fish finder can be moved from boat to boat.
You can also use it during ice fishing and when fishing off a dock.
Some portable units attach to your boat with a suction cup. Notably, this isn’t as stable as a fixed mount.
You may have to adjust a portable unit’s positioning numerous times to achieve the exact angle you want.
Did you know?
A fish finder maps the “structures” – including fish – that it detects via sonar. Owners use this mapping information to determine where fish might be.
STAFF
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How it works
Unless you understand your fish finder works, you might end up spending your day battling electronics instead of fish.
The science behind it
A device called a transducer sends sonar waves into the water. As the waves strike an object – such as a fish or the lake bottom – they reflect back to the transducer. Software measures the rate at which the waves return, calculating the distance to the object. It then turns this data into a graphical representation on a display screen.
What it looks like
Two primary display options exist.
Arch display: This display depicts lines and arches where it has measured objects. You must decipher the lines for yourself, figuring out which returns represent fish. With a full-color display, the returns that have a stronger signal (indicating a larger object) will be darker in color.
Fish-ID display: Some fish-ID units will show a fish or plant shape on the screen. When a fish-ID unit shows a fish shape, the unit’s software is interpreting the data for you.
The fish-ID option could result in some errors, as the unit may misinterpret data. For example, it may perceive a series of plants as a school of fish. But with the arch type of display, you may be able to tell the difference yourself after you get some practice reading the display.
Fish finder technology
Although easy to use, fish finders are actually quite complicated when you delve into their technology. To make the most of your fish finder, it helps to understand the mechanics involved.
Display
As mentioned above, a fish finder has a display screen on which you view its sonar “map.” The quality of the screen plays a key role in your enjoyment of the device. A sharper screen makes it easier to see the water depth as well as any fish in the area.
The average screen resolution is 250,000 pixels. A higher resolution (meaning more pixels) yields a better display quality. To calculate resolution, multiply the number of pixels vertically and horizontally.
In addition to a higher resolution, it’s preferable to get a screen that’s large and bright. A bright screen is easier to see in sunlight, and a large screen is easier to see from a distance. Just like a television, the size of a fish finder’s display is measured diagonally across the face of the screen.
Frequencies
A fish finder’s frequency measurement is given in kilohertz (kHz). Some fish finders make use of multiple frequencies; others are limited to one. Available frequencies usually range from 50 kHz to 200 kHz, although units with other frequencies can be found.
The frequency measurement helps to determine how and where you can use the unit.
Low-frequency units work better in deep water.
High-frequency units excel in shallow water, where you may see underwater plants.
A high-frequency unit generates a sharper display image than a unit with a lower frequency.
GPS
GPS, short for Global Positioning System, plays a key role in fish finder technology.
You can use GPS to mark spots where you had success today, and the fish finder’s software will then help you find those spots next time.
Some fish finders include background maps and charts for multiple lakes. You can use your fish finder’s GPS system to navigate the lake without losing your way.
Power
A fish finder’s power is measured in watts (W). A high-wattage unit creates sharper readings in deep water than a low-wattage unit. Units with higher wattage respond faster, too.
A general rule of thumb says you can receive about 200 feet of reading depth for 100W of power with a 100-kHz frequency.
If you double the frequency, you’ll receive about half of the reading depth for that same 100 watts. And with half the frequency, you can expect to roughly double the reading depth at 100W.
Power sources
Different fish finders use different power sources.
Some run on rechargeable or alkaline batteries.
Some can plug into a cigarette lighter on the boat’s dashboard.
Some connect directly to a trolling motor battery with alligator clips.
Some wire directly into the boat’s electrical system.
Make sure you can meet whatever power needs a particular fish finder has before you buy it. For example, if you don’t own a trolling motor, you probably wouldn’t want to buy a fish finder that requires one.
Transducer
A transducer sends and receives sonar waves. The transducer included with the fish finder device determines the cone angle. (Think of the cone angle as the direction and width of the signal the transducer sends.) A narrow cone angle could be 10 degrees, but some have cone angles as wide as 60 degrees. A 20-degree cone angle is standard for many fish finders.
As you use a wider cone angle, you may lose some sensitivity in deeper water. Some fish finders allow you to swap out multiple cones.
Commonly, a fixed transducer will mount to the edge of your boat. Some pricier models work through the hull of the boat.
With a portable fish finder – the kind you might in connection with a smartphone app – the transducer is placed directly in the water. The transducer may have a float on it to prevent it from sinking.
Others portable units attach to your fish line.
Types of sonar
Fish finders offer three types of sonar.
Downscan
This sonar focuses strongly downward, making it work better in deep water than shallow water. In deep water, it can generate sharp images.
Combination
Both downscan and broadband (see below) are available together in some fish finders. This is an excellent option, and fortunately, the price of these combination units is decreasing.
Broadband
Also called sidescan, broadband sonar works at an angle to the boat, allowing you to see undisturbed water. It doesn’t work as well in deep water as downscan does.
The newest type of broadband sonar is called CHIRP, which uses a type of pulse that yields extremely accurate results. Pairing a CHIRP broadband sonar with a high-resolution display is a strong combination.
"Not all fish finders have GPS; there are some standalone units. These tend to cost less, and they’re great for people who simply want to know what’s below their boat."
STAFF
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Price
You can expect to pay anywhere from $50 to $500+ for a fish finder.
A simple portable fish finder will cost less. However, if you’re looking for a mountable fish finder with a strong signal quality aimed at professional fishermen, you can expect to pay several hundred dollars or more.
Extra and hidden costs with fish finders are minimal. However, you may need to pay for professional installation if you’re uncomfortable drilling holes in the boat yourself. And you may incur costs along the way for battery replacement. Some fish finders need a waterproof cover, too, depending on where they’re mounted.
Tips
Before going on a long fishing trip, you’ll want to have some practice using a new fish finder. Take it to a nearby lake and test it for an hour, learning how the screen looks. If you are using an arch display, this is especially important, as it takes some practice to learn how to interpret the data properly.
For better results in shallow water, consider a dual-beam transducer to cover more area.
A thicker line on the display showing the bottom of the lake represents hard, non-porous lake bed material. You may be able to figure out which fish will be in the area with this information.
The fish finder displays the scene from right to left as you’re moving across the water. Recent results are on the right.
Remember that if you buy a fish finder that interprets data for you (for example, it displays fish shapes on the screen), it could make some errors. These units sometimes read plants as a school of fish and vice versa.
