The 15 Best Fish Finders (2019) Reviews and Buying Guide

Fish finders today are very often more than fish finders. There are stand alone units that are basic sonar to a display and that is all you get. Depending on the power of the transducer will determine what depth and clarity the unit will be able to obtain. 

Far more often when we say fish finger today we mean sonar, map navigation with depth contours, radar, side scan, 3D-images and autopilot. Of course you just tell your significant other that you are going to buy a fish finder! 

In reality what fish finder you need really depends the type fishing being done and the other technology like radar and autopilots that need to be compatible. As a charter captain I like to have state of the art electronics. They really are helpful when you are on a boat for 12+ hours a day. In some case you are paying thousands more just to get a bigger display so it is important to know what you are getting.  

Fish Finder Features – Understanding the Lingo

Fish finders have come a long way over the years and now they’re packed with tons of extra features – some vital to a fishing trip and some simply to make the trip more enjoyable. When shopping for a new fish finder, it’ll be helpful to understand the following terms. Some of these are fantastic additions to a fish finder that you may really appreciate having, others simply drive up the price of the unit with features you may not actually need. It’s important to keep in mind that some of the following terms may have other names signifying similar technologies that are branded by different manufacturers.

GPS/Navigation: If you have a cell phone with Google Maps then you know what this does. GPS equipped fish finders allow you the freedom to ditch the distracting cell phone without ditching your trusty navigation tools.

Satellite Radio: Simply put, new age fish finders are including satellite radios to ensure you’ve got access to your favorite stations despite fishing out in the middle of nowhere! We all know that one spot in the lake that seems to have the most fish but is in between two massive hills that block the radio towers, but with satellite radio, you won’t need to rely on towers any longer!

Chart Plotting: Chartplotters are handy little tools that are entirely location based. It’ll show your current location, past locations, historical depth readings, contours, and depending on the chart plotting software installed, it’ll likely have a slew of navigational tools. These are especially handy in charting specific fishing routes, setting waypoints, marking things of interest or hazards, and remembering hot fishing spots. Recently, chart plotting systems have been aiding in filtering historical information too, evening out sonar imaging discrepancies in temperature, speeds, and water turbulence.

StructureScan: With the implementation of a 3D capable transducer, StructureScan software builds a three-dimensional topographical image of the seafloor that provides significantly more information about the underwater landscape than a traditional 2D imaging processor. With this feature, you’ll better understand where the fish are located and what they’re hanging out next to, such as structures, limbs, rocks, caverns, etc. StructureScan is actually trademarked by the popular manufacturer Lowrance. There are many other similar and/or identical features implemented by other manufacturers by other names such as the Garmin RealVu 3-D.

Bottom Discrimination: Kind of similar to StructureScan, this allows the fish finder to display the actual makeup of the bottom and determine whether its mud, sand, gravel, or rock. This works by analyzing the strength of the bounces from your transducer to determine hardness. This is probably not the greatest fishing tool, but it sure is handy when it comes to determining a good anchor point!

AutoChart: Features like this can be named many different things, such as Humminbirds Autochart Live. These allow you to create an entire real-time chart based on the sonar readings to create your own personal detailed view of the bottom. Furthermore, you can use this tool to compare historic maps with real-time data to determine changes and shifts such as a new depression forming or a structure shifting under the water, especially handy if you frequent specific fishing holes.

SwitchFire: This is a special image post-processing system that filters out the “noise” in a sonar image. Simply put, this makes the image clearer and easier to gather important information from. This system can also help to process images being interfered with by turbulence.

Post-Gain Processing: A handy little software trick that automatically adjusts the entire image, even historical data, with your new display settings. Traditionally, if you changed a setting on your display, you’d have to wait for new data to pop up before the unit uses your new settings, but with post-gain processing, the unit automatically converts all existing information according to the new configuration.

History Scroll Back: Simply put, this allows you to backtrack over previous data your fish finder has displayed but no longer shows on the screen. Handy for comparing different fishing holes and comparing chart plotter data.

Split-Screen and Four Way Viewing: Self-explanatory here. Your display will allow you to set up multiple partitions on the screen to display different data sets and monitoring systems.

Wi-Fish: For our social media fiends out there, Wi-Fish utilizes a black-box sounder and pairs this with your transducer and your smartphone to give you full fish finder capabilities in the palm of your hand, ready to share to social media! No more lame photos of the screen of your fish finder, upload high-quality real-time screenshots and share data of your fishing trip to your pals! As a final note, Wi-Fish also lets you scroll back up to 60 seconds on your smartphone, letting you analyze data that may have already disappeared from your fish finders display.

Here Are The Best Fish Finders and My Review of Each

1. Garmin Striker 4 and CHIRP Transducer Package

Garmin Striker 4 and CHIRP Transducer Package fish finder

Price: Around $100

My review: If you just need a sonar unit in depths less than 50 feet this is a great low cost fish finder that will mark fish and shop accurate depth. 

A major leader in the fish finding tech sector is Garmin, which means you’ll see several of their top models on this list, and for good reason, they’re well made and priced fairly.

The Striker 4 is incredibly cheap at just above a hundred bucks but manages to include a very user-friendly GPS system and a very powerful CHIRP transducer.

It’s affordable, it has what you need, and it gets the job done well with an adjustable transducer that’s capable of fitting the bill in most casual situations.

This particular unit also comes with the Garmin ClearVU scanning function and an easy to use mount. The six-button set up couldn’t be easier to use and it even comes with a built-in flasher for ice fishing or vertical jigging.

Why I like it:

  • 3.5” (also in 5” or 7”) color display and IPX7 waterproofing
  • Waypoint map and the coveted Garmin GPS integration
  • CHIRP transducer that utilizes a 77/200 kHz sweeping frequency band with a maximum depth of 1600’

2. Lowrance Hook2 W SplitShot Fish Finder

Lowrance Hook2 W SplitShot Transducer

Price: Around $550

My review: One of the most intuitive and customizable experiences ever offered in a fish finder, the Hook2 was designed around the idea of automatic adjustments.

That’s right, choose your screen size, transducer type, install, and the unit will automatically adjust its configurations to best match the conditions and type of fishing you’re currently doing, all without the need of human intervention.

Speaking of screen size, the Hook2 is available in either a 7” or 9” display size.

The two are similar, but the 9” version has a slot for expandable memory and better supports multi-view. Choosing a transducer can be tricky, but out of the three offered by Lowrance, I’d recommend the SplitShot as this is likely suitable for most people without breaking the bank.

The TripleShot is a little more advanced and much more expensive while the Bullet’s primary application is for small boats and kayaks, offering a small form factor but fewer features.

The SlitShot transducer is a 2-in-1 sonar package that utilizes both CHIRP sonar technology and Lowrance’s advanced DownScan imaging. These work together to form a comprehensive and complete image of all the swimming creatures, bait balls, and structures under the waves.

The Hook2 comes with very easy to use navigational tools including Navionics, GPS plotter, pre-loaded C-MAPs, and a birds-eye view of 1’ contour lines on over 4000 different bodies of water in the US.

Why I like it:

  • 7” or 9” display size options, both utilizing the latest SolarMAX high-resolution screens
  • SplitShot transducer package offers the best of both economic value and high functioning sonar technology
  • Fully automated sonar configurations that actively adjust according to real-time data

3. Lowrance HDS-12 Live Fish Finder

Lowrance HDS-12 Live fish finder
Price: Around $3,000
My review: Another fish finder jam-packed with the latest tech gadget features, the Lowrance HDS-12 Live is fully capable of integrating with your mobile device via WiFi connectivity and touts the most advanced fish finding technology to ever hit the market thus far.
 
It’s got everything you could ever want, including StructureScan 3D, StructureScan HD, Mercury VesselView Link, and Lowrance’s Outboard Pilot software.
 
There is so much to talk about regarding this unit that it would warrant its own entire page!
 
The sonar is in a proprietary color scheme that utilizes high-visibility contrast to enhance the usability of its advanced sonar capabilities. Speaking of sonar, this unit does it all, from down and side sonar to full 3D and HD scanning, the quality is unmatched. Of course, it comes with a powerful 10Hz GPS system that supports WAAS, EGNOS, and MSAS.
 
A huge advantage to using this fish finder is its capabilities of tethering together multiple sonar systems to create an all-encompassing 3D image scan. With the HDS-12 Live, you’ll be able to mount multiple different transducers on your watercraft and link them together to create a full sonar network.

Why I like it:

  • 7”, 9”, 12”, or 16” high contrast high-resolution display options available
  • Highly advanced sonar systems including Structure Scan 3D HD utilizing a network of different transducers
  • Top quality navigation tools including a 10Hz GPS antenna, Navionics+, C-Map, Max-N+, and many other navigation tools

4. Humminbird Helix 5 G2 CHIRP Chip Package

Humminbird Helix 5 G2 CHIRP Chip Package fish finder combo

Price: Around $180

My review: This horizontal wide screen fish finder is an incredible purchase at just over two hundred bucks.

You’ll get built-in GPS capabilities, Humminbird’s 2D low-power sonar system, SwitchFire detailed bottom charting, both wide and narrow beam configurations, and a powerful 4000W sweeping frequency CHIRP transducer capable of both down imaging up to 2500’ and clear side imaging.

Humminbird has a nice little collaboration with LakeMaster and NOAA that allows them to include powerful base maps from the most trusted fishing sources.

If you don’t like those, or would like to create your own, you can! With Humminbird’s powerful Live Autocharting feature, you can record up to 8 hours of custom charting, all recorded seamlessly as you boat about.

Why I like it:

  • 5” multi-view capable color display with tilt mount included
  • Expandable SD memory for additional waypoint and map storage
  • An internal GPS system, chart plotting, and Anima Cartography

5. Raymarine Axiom With RealVision 3D and RV-100 Transducer Package

Raymarine Axiom With RealVision 3D and RV-100 Transducer Package

Price: Around $780

My review: This is really one of the most feature-rich technologically advanced units on the market today and boy it sure is beautiful!

It’s powered by a quad-core processor running on the famous Lighthouse 3 operating system. These are available in either 7”, 9”, or 12” displays.

This multi-touch interface is by far one of the highest resolutions and best overall looking screens I’ve seen in fish finders.

The feature list is likely longer than your families grocery list, including RealVision 3D image processing, SideVision, DownVision, 3D fish finder, and powerful CHIRP sonar.

The RV-100 transducer is a CHIRP enabled 600W monster with the option to use dual beam 50/200kHz frequency configuration. This unit is capable of displaying sonar imaging from the side, underneath you, and in the RealVision format all on the same screen!

The Axiom fishfinder comes with full mobile integration via WiFi connectivity that allows you to transfer and save data and also control most of the features on the unit itself from your smartphone.

You’ll also get Navionics+ charting programs that cover over 20,000 bodies of water in the US and Canada.

Worthwhile mentioning, this thing is absolutely insane when it comes to functionality. You can watch Netflix, stream Spotify, integrate with drones or security cameras, and add more radar functionalities. This is truly full-service boat media hub that so happens to be highly effective at finding fish! If you don’t mind paying a premium for a beautiful and powerful technological upgrade for your precious watercraft, this is the fish finder for you!

Why I like it:

  • 7-12” ultra-bright display with a powerful 600W RV-100 transducer
  • Essentially an onboard computing system running on a quad-core processor and Lighthouse 3 operating system
  • RealVision 3D sonar, CHIRP side and down vision capable, and active Sonar Charting to create all-encompassing bathymetry charts

6. Garmin Strike Plus 4 and Dual Beam Transducer Package

Garmin Strike Plus 4 and Dual Beam Transducer Package fish finder

Price: Around $140

My review: The same Striker we love from the previous review with a slightly larger and better contract display and a dual beam transducer set-up, meaning you can use the CHIRP equipped sonar over a wider area of coverage.

This model is a bit better for those of you wanting a bit more control over the sonar configuration. Like the Striker 4 base model, this one includes the Garmin ClearVU 3D scanning function and also utilizes a 6 button layout, just in a slightly larger form factor that I personally prefer!

Why I like it:

  • 4.3” color display with IPX7 waterproofing
  • Equipped with the Garmin GPS and waypoint mapping system
  • Dual beam CHIRP transducer that sweeps through 50/77/83/200 kHz

7. Humminbird PiranhaMax 4.3 W Down Imaging

Humminbird PiranhaMax 4.3 W Down Imaging fish finder
Price: Around $150

My review: Not as well known as Garmin but arguably of similar quality, Humminbird’s PiranhaMax is a neat little 4.3” fish finder. This particular unit focused on downward imaging and touts an impressive 2400w peak power output.
 
Humminbird’s Fish ID+ makes spotting fish a breeze and since there are only 4 buttons, this unit is extremely user-friendly. To make matters even better, its equipped with dual beams, allowing for a fantastically wide range of down imaging.

Why I like it:

  • 4.3” color display with a swivel mount included
  • Dual beam down imaging capable of looking down up to 600’ in a narrow or wide beam angle configuration
  • Equipped with adjustable fish alarms, depth alarms, and more

8. Garmin EchoMap and CHIRP Transducer Package

Garmin EchoMap and CHIRP Transducer Package
Price: Around $275
 
My review: A slightly more pricy offering from Garmin, the EchoMap is extremely similar to the Striker series, except, you guessed it, it offers the Garmin LakeVU HD maps, U.S. Bluechart G2 maps, or LakeVU Canada maps.
 
As with most of the fish finders Garmin offers, it’s equipped with the coveted 5Hz GPS system that has a refresh rate of five times per second, making your positional data extremely accurate and returning to waypoints a breeze.

The transducer included here blasts through the waves with 500W of power using a sweeping frequency CHIRP CV chip. The CV CHIRP transducer is capable of both down imaging and side imaging via the Garmin SideVU technology.

There are two versions of the Garmin EchoMap unit and I’ll review the other as well so you can see the difference!

Why I like it:

  • 4” color display with swivel mount included
  • Floats
  • Garmin Echo Mapping technology capable of both down and side imaging with 500W of power
  • Garmin Bluechart G2, US LakeVU, or Canada LakeVU map options

9. Garmin EchoMap 53CV Fish Finder

Garmin EchoMap 53CV fish finder

Price: Around $340

My review: I promised to review both of the Garmin EchoMap devices, so here is the second one! Basically, you can buy the EchoMap with the buttons on the bottom or the buttons on the right-hand side.

Aside from that, they usually come with different transducer packages but you could use either version with any compatible transducer. Besides the different button layout and a slightly wider screen, the two units are very similar and both include the famous Garmin LakeVU, ClearVU, and SideVU features.

If you didn’t catch it before, the LakeVU HD feature includes over 17,000 lake maps with one-foot contours from shore to shining shore.

Of course, just like the other EchoMap, this one comes with the handy dandy Garmin 5Hz GPS system with 5 refreshes per second and active waypoint setting. It also includes a swivel mount and that powerful 500W CHIRP dual beam transducer we talked about with the other EchoMap device.

Why I like it:

  • The same 4” color display as the other EchoMap, just with the buttons to the right instead of underneath
  • Garmin LakeVU and Bluechart G2 charts feature that allows you to set up to 5000 unique waypoints and includes pre-loaded maps of over 17,000 lakes
  • Top tier Garmin 5Hz GPS equipped with 5 per second refresh rate

10. Garmin Striker Plus 5CV W/ CHIRP GT20-TM Transducer Package

Garmin Striker Plus fish finder

Price: Around $300

My review: Another revamp of a similar model, the Striker Plus 5CV is similar to the other Striker models on this list but instead of having the buttons underneath the display, this model aligns them on the right-hand side with a wider screen.

The display is capable of split-screen viewing configurations and includes split-screen zooming. Of course, you’ll be getting your hands on that sweet Garmin ClearVU scanning technology which allows for incredibly concise and clear downward imaging, capable of creating imaging contours at 1’ margins.

Furthermore, you’ll get the power of Garmin 5Hz GPS which is capable of being used as a split screen with your fish finding or imaging display.

Why I like it:

  • 5” color display readable in sunlight with right-hand button configuration on an included tilt-view mount
  • Garmin ClearVU downward imaging sonar technology with Garmin QuickDraw contour mapping software, capable of storing up to 2 million acres of custom maps
  • CHIRP transducer sweeping frequencies in the range of 50/77/200kHz at 500W of power

11. Simrad GO5 XSE Transom Mount Transducer Package

Simrad GO5 XSE fish finder

Price: Around $470

My review: This beautiful product from Simrad offers us something different than the traditional rugged designs in that it has a very slim and clean appearance.

Although it’s appearance seems simply, this fish finder is packed to the brim with helpful features including a bright backlit touch screen, TripIntel trip planning software, NMEA 2000 compatibility, Navionics compatibility, and C-Map routing compatibility.

The GO5 is the smallest in the series and lacks a few features that the larger 7” and 9” display versions have, such as NMEA overlays. Of course, that will also cost significantly more!

The Simrad GO series includes a powerful 10Hz GPS receiver and has on board a powerful full-featured chart plotter. Get your data in real time in the palm of your hand with the built-in wireless networking options.

The included transom mount transducer utilizes TotalScan and StructureScan HD, which are better explained in the guide. This particular transducer is a dual band capable of operating on either medium 455 or high 800kHz frequencies. This powerful HDI skimmer combines several data points such as depth, temperature, and structures with its innovative FishReveal software, which creates a specialized custom view of fish and structures. The fish finder itself is capable of being used with a CHIRP transducer (not included).

Why I like it:

  • 5” bright backlit display with an included bracket mount (many people buy this unit to mount flush with the dashboard or other surfaces in their boats)
  • GoFree Wifi connectivity allows for smartphone integration
  • GO series offers the widest available cartographic chart plotting software with integrations from Insight, Navionics, and CMAP

12. Humminbird Helix 7 CHIRP DI G2 Fish Finder

Humminbird Helix 7 CHIRP fish finder

Price: Around $480

My review: The Helix 7 CHIRP DI package from Humminbird is an excellent mid-range choice for those of you starting to upgrade from your standard fish finders.

The Helix is available on Amazon in a few different packages with and also without transducers, so if you wish to choose your own, make sure you select the package which contains only the display unit.

I chose to review the DI GPS G2 package as I think it’s a fantastic deal and will likely suffice for what most people need.

The 7 in the name suggests it has a 7” display, and the display sure is beautiful, one of the best mid-sized displays on this list. It’s extremely bright, has an incredible resolution, and is easily readable even in direct sunlight.

The unit comes equipped with a powerful GPS receiver that offers your choice of storing 2500 waypoints and 50 different custom routes. This unit also comes equipped with an expandable storage slot fit for a single Micro SD card, in case that 2500 waypoints weren’t enough! To boot, the unit comes with Lake Master, Auto Charting Pro, and Navionics+, which should pretty much cover all of your navigating and charting needs.

Why I like it:

  • 7” WVGA sunlight readable display
  • Powerful 4000W CHIRP downward imaging transducer with SwitchFire dual beam capabilities
  • GPS, Lake Master, Auto Charting Pro, Navionics+, integrated UniMap Cartography, and expandable memory to store waypoints and routes

13. Lowrance Elite-12 TI2 W Med High Skimmer Transducer

Lowrance Elite-12 fish finder

Price: Around $2070

My review: The Elite-12 TI is the premium level of the Lowrance lineup. Here you’ll find those make or break functions that are more than worth the money if you’re serious about fishing. Let’s start with one of the biggest difference makers here – the transducer.

Lowrance has developed its own proprietary CHIRP equipped transducer called the Med/High Skimmer. This transducer has quickly become a top choice among fisherman from both the entry level to the most advanced fishing operations.

This HDI transducer utilizes the power of DownScan Imaging processing and it’s multi-beam Med/High CHIRP sonar to create powerful photo-like images of structures, fish coverage, and target differentiation.

Something that truly stands out with this particular imaging system is its ability to track and portray each individual fish in a tightly packed school of fish where other units may only be capable of showing a solid mass of blobs. Furthermore, using StructureScan HD, you’ll be able to identify very clearly where and what the fish are congregating around with ridiculous precision and image quality.

The actual display is a beautiful and touch capable 12” monitor with Trackback software, allowing you to review historical data no longer displayed on the unit. This allows you to easily compare and return to areas of interest and since the Elite TI comes with intuitive navigation tools, you’ll be finding and saving the locations of each and every one of the best fishing spots!

The system as a whole is highly connective with full mobile phone integration via WiFI and Bluetooth connectivity. You’ll have access to MotorGuide Xi5 trolling motor software, C-MAP Genesis updates, Power-Pole Anchors, SonicHub 2 marine audio, and more. Furthermore, your system can connect with NMEA 2000 to provide instant access to engine monitoring software, waypoint location sharing, and SmartSteer trolling navigation.

It’s important to note that there are smaller and less expensive Elite models available, but some may lack the features of the larger units, such as the Elite 5 TI not having MotorGuide control.

Why I like it:

  • 5”, 7”, 9”, and 12” SolarMAX high-resolution touchscreen display options with multi-view configurations
  • Incredible connectivity offering full mobile device integration, control, motor data, and several other software goodies such as preloaded and updatable C-MAP charts, FishReveal smart targeting, SmartSteer, NMEA 2000, and Power-Pole Anchor controls
  • Powerful Med/High Lowrance transducer with StructureScan HD, 455/800kHz down and side imaging, and TotalScan compatible

14. Raymarine DragonFly 7 Pro W Wide Spectrum CHIRP Transducer

Raymarine DragonFly 7 Pro fish finder

Price: Around $800

My review: The DragonFly line has quite a reputation in the world of competition anglers and lucky for us, it’s actually priced incredibly low for such a premium build quality and its array of amazing features.

Starting with the display, the Dragonfly has a line of multiple sizes starting at 4” and reaching up to 7”. I highly recommend the larger screen as it does contain a lot of features not found on the smaller versions for a rather small price increase.

The actual screens on these units are optically bonded LCD high-resolution displays, which up until now, was only something you’d see on the ultra-expensive fish finders. In a nutshell, this means you get an extremely durable and IPX7 waterproof unit that also has a very bright and vibrant color display with super sharp contrast. In my opinion, this is one of the best displays on a fish finder under a thousand bucks hands down.

The transducer this unit comes with is a specialized CHIRP DownVision sonar unit that utilizes both an Ultra Wide beam angle and a focused fish targeting beam. This means you’ll be able to achieve highly accurate bottom scans even at 600’ below, while also being able to switch over to a powerful fish targeting specific beam to triangulate on those sweet spots.

Of course, the Dragonfly comes with a lot of the technical goodies we know and love, including built-in WiFi connectivity for your smartphones and a mobile “Raymarine Wi-Fish” application that allows you full control over the fish finder from your phone.

This bad boy comes equipped with Navionics SonarChat Live, which allows you to update your onboard maps storage and access the newest bathymetric chart data. The built-in GPS comes equipped with a 10Hz antenna and works with C-MAP or Raymarine Lighthouse charting software.

Why I like it:

  • 7” optically bound high-resolution LCD screen
  • Powerful dual channel DownVision equipped sonar technology capable of scanning down to 600’
  • Full smartphone integration via WiFi allows you to update your units maps, control and view fish finder data from your phone, and access applications such as music and navigational tools

15. Lucky Portable Fish Finder (Cheapest)

Lucky Portable Fish Finder

Price: Around $45

My review: This is one of the most affordable fish finders worthwhile on the market. It’s portable, simple to use, and has roughly 5 hours of battery life.

It’s a handheld device that utilizes a floating transducer, which makes this especially useful for those of you fishing from the bank or in a kayak.

The backlit display is simplified, showing fish depth and other major structures.

Why I like it:

  • 24’ floating transducer cord
  • Uses 4 AAA batteries to achieve 5 hours of usage time
  • Maximum detectable depths at 328ft with a 45-degree beam angle

16. Deeper Pro+ Smart Portable Castable Sonar

Deeper Pro+ Smart Portable Castable Sonar

Price: Around $200

My review: Something a little different here is the Deeper Pro+ castable sonar unit, which is simple to use and extremely effective for those of you fishing from the bank or a kayak.

Like the title suggests, you attach this to your fishing pole, cast it out into the water, and then using the power of WiFi, you obtain all of that sweet information regarding the whereabouts of those pesky fishies. But wait, there’s more!

This bad boy has built-in GPS and will automatically build contour maps for your viewing pleasure. Figure out where your favorite lures will get lost BEFORE casting them into oblivion. Of course, you’ll also get depth data, water temperatures, and several other tidbits of important information.

If you buy the gift kit, you’ll get a night cover which lights up your fish finder, a Gerber multi-tool, a tactical looking smartphone holder, and a nice little carry bag.

Why I like it:

  • A compact little portable orb form factor that's easily cast into the water and streams live data to your smartphone
  • Capable of casting out 330’ and scanning to depths of 260’
  • Deeper app that can store and share information with ease

Fish Finder Buying Guide – Beginner to Expert

What is A Fish Finder?

Fish finders are an evolutionary piece of sonar technology that was originally found in the form of a fathometer. The fathometer was widely used for navigation, displaying the water depth and other general oceanographic information. The root word of fathometer, the fathom is a unit of measurement for water depth.

Fathometers worked by transforming electrical pulses into sound waves via an underwater transducer (AKA Hydrophone) and using the reflected sound waves to record data, such as size, composition, shape, depth, location, movement direction, etc. The reflection data is gathered using some pretty complex math equations, which we’ll talk about more in depth in the next section.

The original fathometer used for recreational purposes used a rotating ray of light at the edge of a circle which flashed with every echo received, which is how it showed the user depth. The faster the flash, the closer the bottom was to the boat. In bright light on a sunny day, this was terribly difficult to utilize and to make matters worse, if the waters were rough, they were nearly unusable due to accuracy issues. Furthermore, they gave off brief quick flashes indicating fish, but a quick couple of flashes was all you got in terms of fish finding functionality.

Some really smart oceanography scientists (anglers at heart) realized they could use similar technology to find the location of the creatures swimming under them and display them onto a screen with a limited amount of tracking over time, thus, the modern day “fish finder” is born.

How Fish Finders Work

This section will be a bit technical, so if you don’t care about the math and science behind fish finders, you could skip this section! If you’d like to learn more about fish finders as to better interpret their data and set yourself apart from the weak anglers, read on!

Starting with math, fish finders use this approximate equation to determine the speed of it’s manufactured sound waves through water: C = T – T^2 + S + D.

C is the speed of sound (m/s)

T is the temperature in Celsius of the water

S is the salinity per mile (amount of salt in the water)

D is the depth of the water currently being measured

A modern-day fish finder will re-record and calculate this data up to 40 times per second and charts this data on a graph.

We mentioned that the fish finder is sending sound waves through the water to determine the distance and position of fish and the sea floor. How sensitive (the frequency of sound waves) will determine the amount of location accuracy. Using a higher frequency will result in much faster display times and more accurate and more detailed displayed, however, higher frequencies penetrate matter with less efficiency, making lower frequency superior for extreme depths. Most instances of commercial fishing such as deep sea trawling use an optimum range of frequencies in the 50-200kHz, making their display a bit less detailed than what you’d use to go bass fishing with.

When looking at the graphical display of your fish finder, it’s important to note that what is in the middle of the screen isn’t always what is directly under your boat. Instead, the x-axis is actually showing time, meaning the left portion of the graph is what your transducer has already passed over and recorded. What’s directly under your transducer is at the far right in most units.

Keeping this in mind, lower end units fail to track this data accurately at high speeds. If you’re traveling at high rates of speed, the graph may lack data and will be less accurate, creating imaging distortion. Image distortion is heavily based on the speed of your vessel versus the update rate of the fish finder. This means that if you plan on locating fish while on the move, you’ll need to opt for a fish finder that has a high refresh rate, close or at 40 refresh rates per second.

Another interpretation tip includes something called “fish arches”. The newer more advanced units are getting better at solving this problem, but most units on the market today still suffer from fish arches. In a nutshell, a fish arch is shown on the fish finders display as an odd arch off the bottom of the sea floor and not an actual fish icon. This happens due to a fish entering the leading edge of the sonar beam, activating a display pixel and recognizing there is something there. As the fish moves towards the center of what your sonar is recording, the distance from the fish to the bottom of your boat decreases, tricking your fish finder into thinking the depth is reducing and that the boat is nearing the sea floor. As you pass over the fish, the sonar begins to display a drop off as the fish gets further away from the bottom of your boat and voila, you have an awkward arch displayed on your fish finders screen!

Fish arches can happen frequently when there are large numbers of fish all gathered up together or there is a school of tightly packed bait fish. To identify whether or not there really is some kind of structure underneath you or it’s fish, you’ll have to pay close attention to the thickness of the lines given to you on the display. Schools of fish will usually display a very thin line around the arch that otherwise should be thick if it really was the seafloor.

As a last little tip for interpretation, some fish finders are capable of picking up on your fishing line and the lures attached to them. You may notice slim lines falling from the top to the bottom, and you guessed it, that’s the path of your gear! In optimal temperatures and water oxygen levels, you can use this to determine the depth of your lure set.

Fish Finding Power

I’ve mentioned how important the frequency at which your fish finder operates in before, but let’s go ahead and expand on that so you can find the perfect unit for your situation.

A quick recap of what I mentioned before, the higher the frequency, the higher the detail your fish finder will offer, but high frequencies cannot penetrate as deep as lower frequencies, decreasing their range.

High frequencies = less range and area of view but offer higher definition

Low frequencies = higher range and more area of view but at a cost of lower definition

For shallow-water angling less than 200 feet, I’d choose higher frequencies such as 200kHz to 800kHz, and for depths exceeding 200 feet, I’d recommend 80kHz or even lower, at 50kHz for extremely deep fishing.

Fish finders can come in a variety of frequency capable modes, including single band, dual band, multi-band, or broadband CHIRP systems.

Single frequency fish finders will likely be cheaper but only offer one frequency, meaning you should purchase this particular unit for a particular type of fishing and depth.

Dual band equipped fish finders typically have a high and a low setting, letting you switch between two general levels, offering more of a range in the depths your fish finder will excel in. Some of these may also transmit in both available frequencies at the same time, offering the best of both worlds simultaneously.

Multi-band fish finders will either have several presets you can choose from, giving you a wide variety of choices or they will allow you to specifically choose a frequency, giving you ultimate fine tuning control over your fish finders transducer.

Compressed High-Intensity Radar Pulse (CHIRP) systems use a linear sweeping method that gradually increases the frequency to find incredible detail at the most efficient frequencies possible. Think of this as an automatic adjusting style of fish finder. An example of this would be a sweep from 40 to 80kHz, 120 to 250kHz, 400 to 800kHz, and so on. These are best used for extreme depths, such as 10,000 feet.

CHIRP fish finders actually utilize and send less total peak energy than other fish finders, however, their modulated wide-band pulses are much longer in duration and can put up to 50x more energy through the water. CHIRP equipped devices use digital pattern matching and signal processing to achieve much greater resolution levels than their non-CHIRP counterparts and have the ability to target individual fish at great depths that are only inches apart from each other. Most fish finders without CHIRP will identify groups of fish as one solid mass, but a CHIRP equipped unit can identify each and every fish separately, giving you an accurate estimation of how many fish are available and where each one is specifically.

Another important aspect of a fish finder is the wattage or overall peak power capability of the unit. The measurement you’ll see is in watts RMS (root mean squared). The amount of power a fish finder is capable of producing will determine its ability to blow through silt and light debris, achieve greater depth ranges and identify specific targets.

Inland lake fishing only necessitates roughly 200W while anything less than deep blue fishing would likely only need roughly 500W. Deep sea fishing may require 1000W or more to reach the required target depths.

Finding the perfect frequency, whether it be a single frequency unit for the weekend lake dweller or a CHIRP equipped monstrosity and pairing it with the proper wattage level is crucial for optimum fishfinding experience.

Directional Targeting

Yet another specification you’ll need to widely study and pay attention to before you take the plunge on a new fishfinding unit is the directional area of view the fish finder is capable of. Some fish finder transducers have 360-degree capabilities, but of course, those are the more expensive options and many people may not need that.

Side imaging utilizes thin beams of sonar to scan 180-degrees roughly 240 feet left and right of your watercraft. This aids the fish finders computer chip in rendering a more accurate picture of the seafloor.

Down imaging is pretty self-explanatory and what most typical fish finders do. These shoot sonar waves down from their mounting point to create an image of what’s underneath your watercraft.

360 Imaging is basically side imaging on steroids. This is especially useful for net casting as you’re able to avoid potential snags and mark structures hidden just beneath the surface in any direction of your transducer.

Something popular you’ll likely come across when comparing the specifications of units is the “beamwidth” or “cone angle”. Simply put, this is how wide the beam is that is coming out of your transducer and gathering that sweet honey hole of information.

Fully explaining beam angle would really be better suited in a guide of its own, so I won’t go there for now. However, I will provide some tips and tricks here to help you get on your way!

A narrow beam angle is best used for specific locations, such as wreck and structure fishing. A beam angle of 9 to 15 degrees makes for incredibly focused detail due to the sonar energy being cast into one small area, creating a higher resolution picture. This helps define edges and barriers the structures may contain, making lure placement much easier. With a narrow beam, you’re sacrificing total area scanned for higher detail, which makes finding fish on the move a more difficult task.

A wider beam angle greatly raises your chances of picking up fast moving fish or finding fish while you’re motoring around. Wide beams such as one in the range of 40 to 45 degrees are excellent for fishing tournaments as they greatly impact how quickly you find pockets of fish. Mixed with an extremely powerful transducer (high wattage) and a low frequency, these are among the best at generally spotting fish and locating a potential sweet spot. The downside to using a wide angle is that structures aren’t as crisp looking, making edges less definable and things lying on the bottom a total blur.

A medium beam angle, such as something in the 20 to 30-degree area, makes for a decent middle ground of detail and coverage. You’ll sacrifice pinpoint details that will make edges of structures appear slightly blurred and you won’t be able to cover as much ground as a wide angle, but you’ll essentially get a best of both worlds scenario.

Beam angle, frequency, and power all work together to create the picture you receive on your display and to help you find productive waters, so it’s important to understand all three of them and choose something that fits your style of fishing. All three of these components need to match up and play to each other’s strengths. To do this effectively, you need to plan ahead and have a rough idea of what type of fishing you’re going to be doing, how deep those fish will be, and how difficult it will be to find them.

For example, using highly penetrative frequencies such as 50kHz with a low powered wide beam wouldn’t make much sense because the frequency would be best used for deeper water while a low powered wide beam wouldn’t be capable of delivering much detail at great depths.

If you’d just like an end-all-be-all piece of advice unless you’re competing or very serious about fishing, I’d recommend you to just get a 20 or 25-degree cone angled down imaging transducer and be done with it.

Your Boats Relationship With The Transducer

Aside from power, frequency, and beam angle, we have to consider how the construction of our watercraft affects the efficiency of our transducer and vice versa. Many fish finders meant for recreational usage come with a transducer and most of the popular brands offer their fish finder units with a range of different transducers. For the higher end and competitive level gear, anglers generally purchase the fishfinding unit they want and pair it with a transducer of their choosing.

Thru-hull units: These can be challenging to install properly, but once done, these offer some of the highest quality signals.

Sailboats and displacement powered boats can benefit from using in-hull mounted transducers because this creates less drag, which is important to a non-motorized boat.

Fiberglass hulls generally not more than ⅝” thick work great with in-hull mounted transducers as well.

In-hull units: These are units that don’t require actual water contact and instead are installed inside the hull via glue, silicon, or epoxy. These won’t be a good choice if your watercraft has steel or a cored hull and for the most part, in-hull units are best used in solid fiberglass boats.

Transom-mount units: These units mount on the transom of your boat (the back) and are usually adjustable, allowing you to change the angle on the bracket. These mounts are secured by screws and/or bolts and although easy to install, they will feel the full force of the water passing by them.

Transom mount transducers are optimal for planning hulls less than 28’.

Trolling motor compatible units: These can either be mounted on the outside of the trolling motor or inside the propeller hub and can be either clamped for easy to remove access or permanently installed.

Fish Finder Networking

In the world of fish finders, you have many options when it comes to functionality and networking capabilities, thus making it important to plan out how you’ll be utilizing your tech, which boat it’ll be implemented inside of, and what functions you need.

Standalone fish finders are fish finders and that’s it. It tells you if there are fish under you or not, and that’s all you get, no fancy features, no music, no GPS, nada. These are perfect for those of you who already have other products fulfilling your needs and the last piece to your set up is a simple fish finding solution. These are among the cheapest units on the market and some of them come as standalone units with the option of adding more components later.

Combination fish finders typically marry a traditional fish finder with one or a couple of other handy features, such as GPS or a chart plotter. These are probably the most sensical solution for most people who own mid-size boats.

Fully networked systems are all-inclusive tech products for the true boating and fishing enthusiast. These typically have all the bells and whistles and are compatible with multiple displays, smart-phone integration, chart plotting, black box duties, Bluetooth and WiFi compatibility, satellite radio, radar, GPS, etc. If you really hate having multiple pieces of equipment to fondle around with and are tight on space, a well-networked fish finder may be the perfect addition for a clean all-in-one set up.

Multiple-display networked fish finders are perfect for larger vessels as they are capable of providing you with a multitude of easy to read data all at once, without the need to flip through channels or fumble with buttons to find the right screen.

Furthermore, as a final option in the mix, there are portable fish finders. These are not nearly as feature rich or accurate as a full-blown properly installed fishfinding unit, however, they are great for those of you who travel often and rent multiple different watercraft. These include a display unit, a mount, a transducer, and a battery pack in an all-in-one form factor. Some of these simply use an easy to mount system, while others actually float in the water next to your watercraft.

Displays Explained

Nearly all of the fish finders on the market today with a display are using an LCD panel with lots of specifications that may be difficult to understand if you’re not technologically inclined.

First and foremost, you’ll need to make a choice between grayscale and color right off the bat. Color displays are automatically going to run you more money, but offer much greater detail and increased accuracy by displaying varying levels of color for varying levels of density.

Next, you’ll need to choose a display size. Typically, fish finders range in the 3.5” to 10” size range. For simple single duty fish finders, small sizes are perfectly fine and will get the job done, but if you’re choosing a fish finder that displays lots of information, you may find that a small screen becomes quickly cluttered and difficult to read. Some multi-functional fish finders may also display information in a split-screen configuration, making those super small screens nearly useless in this regard.

LCD panels are constructed of grids of pixels which are tiny dots that are individually color controlled when an electrical current passes through them. The more pixels an LCD display contains per square inch, the higher resolution the screen will be, meaning it will be easier to read, brighter, and have better picture quality.

The number of vertical pixels will determine the depth resolution while the number of horizontal pixels will determine how much data is shown on the screen before new data replaces it, pushing the old data off the screen.

High-quality displays are a heavy “get what you pay for” type of specification. Cheap fish finders have likely cut costs so low due to having very low-resolution LCD displays, while expensive fish finders utilize the leading edge technology behind LCD displays to deliver an incredibly high resolution.

So, does it matter how good your display looks and should you spend the extra dough to get more pixels? In most cases, it simply depends on what you require from your fish finder. A higher resolution display has many advantages and will enable you to see smaller details, better estimate distances, aid you in finding the perfect lure depth, determine game fish versus baitfish, etc.

If you’re fishing for sport and you’re actually competing against other people, having an ultra high-definition fish finder could literally be the difference between winning and losing. On the flip side, if you’re just out on the lake to enjoy some brews just want to know if it’s worth dropping your lure in a specific spot or not, a high definition LCD display might be a waste of money.

High-resolution taglines don’t always signify a quality display, though. Some manufacturers have phony high pixel density while sacrificing contrast quality, making that incredibly high amount of pixels utterly pointless. Low contrast means your screen will be difficult to use in bright light, so it doesn’t matter if you have a high-resolution screen if you can’t see it! You’ll need to pay attention to both pixel density and contrast levels, ensuring that not only does it meet your resolution requirement but the resolution is actually usable and sharp looking.

Freshwater GPS vs Saltwater GPS?

I mentioned before that the composition of the water you’re operating in changes the game in terms of fish finding gear, let’s dive a bit deeper into that!

Obviously, salt water is full of sodium chloride. When water is saturated with salt, it’s called salinity, and salinity adds a great deal of density to the water. Since fish finders work by turning electrical impulses into sound waves and then listening to hear the bounce back of these sounds waves, it’s no surprise that denser water makes the job of a fish finder more difficult.

Furthermore, the temperature of salt water also plays a major role. The warmer the salt water, the less dense it is compared to colder waters. This is why your fish finder being able to calculate the temperature of the water or be calibrated accordingly is important to achieve the most accurate information.

You may find on the market some fish finder transducers that are specifically labeled for salt or fresh water. The truth is, you can use either transducer in either type of water, however, the penetration levels of the frequencies your transducer is using will vary. A transducer that performs extremely well at high frequencies and relatively deep may not perform nearly as well when dipped into salt water. Conversely, a transducer that you’ve managed to get working well in salt water may have attributes or a calibration that is overkill for fresh water. Many of the labelings you see on specific transducers really just relate to how power hungry it is. They may have similar models where the only difference is the amount of power and price tag.

As a general rule of thumb, your super low power consuming transducers will not perform nearly as well as power-hungry models in salt water. On the flip side, buying a high power output capable transducer for use in freshwater may simply be a waste of money and if you’re kayaking, powering it off of a standalone battery cell, it may be a waste of energy, reducing how much time it will operate until you need a fresh battery or a recharge.  

At the end of the day, transmission efficiency through salt water and fresh water are basically negligible. If you know you’ll be spending 100% of your time fishing in one or the other, sure, opt for a unit that specifically performs well in that type of water, but for the most part, how well your fish finder and transducer works is going to come down to power and frequency versus depth. If you’re fishing in shallow salt water, there is no reason why you can’t use a “freshwater” fish finder, it’ll work just fine.

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