Often the first fishing high tech that anglers explore, traditional mounted fish finders are transforming into data hubs for networked fishing technology. On the other end of the spectrum, portable castable fish finder transducers are introducing high technology at price points accessible for all anglers.
What's Down There?
Fish finders (sometimes written fishfinders) evolved from depth-finding fathometers. Initially carried as a safety measure to prevent ships from running aground, these devices used electrically generated pulses of noise to detect the depth of the water a boat was navigating.
Refinements in this sonar-emitting transducer technology eventually turned these fish finders into the consumer electronics we know today.
In their simplest form, fish finders depict two areas of data:
- Bottom - This is the sound signatures of the waterway's floor and the related bottom structure that depict sunken features that can attract fish.
- Fish arches - As a moving boat passes over a fish suspended in the water column, its distance and aspect ratio change. The signal starts far and narrow, then closes and broadens, then becoming far and narrow again. When shown as a side-scrolling depiction of the water column in time, these signals translate into tell-tale crescent fish arches.
Fish finders' transducers emit sonar pulses at different frequencies, recorded in kilohertz (kHz), and at different cone angles (shown in a degrees of the angle being emitted down from the transducer). Different frequencies and cone angles have different purposes.
Low frequencies can penetrate deeper into the water, while high frequencies give better detail. Wide cone angles cast a broader net while searching for fish, while narrow cone angles are better at isolating individual fish and how they're interacting with bottom structure.
Modern fish finders combine rotating frequencies and even multiple transducers to synthesize better imaging.
This data is aggregated and shown to the angler via the fish finder's user interface, nowadays typically tablet-like flat-screens of varying dimensions depending on a fish finder's intended use. Hardwired to the transducer, these user interfaces can either be a control-less touchscreen, or have mechanical buttons, or be a hybrid of the two.
Typically a fish finder's screen is mounted close to an angler for easy access and reading. Because the user interface is in that prime location, it's a natural evolution for the fish finder to become the electronic hub of a networked fishing boat.
The Future of Fish Finders
In the past few years, fish finder user interfaces have added even more functionality. As GPS receivers have dropped in price, it's now common to see mapping features on all but the most entry-level units.
Even more recent developments are disrupting the wired connections of traditional fish finders. Some fixed and even a new category of castable fish finders are connecting to their user interfaces via WiFi and bluetooth. Those user interfaces can now even be an angler's own smartphone or tablet.
The Best Fish Finder 
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Traditional Fish Finders
These manufacturers focus on traditional, fixed transducers that come with mounted displays.