Fish finders, also known as depth finders, are small sonar units that help anglers identify underwater features and also, if the unit is powerful enough, locate schools of baitfish and individual predator fish.
Purchase the most powerful fish finder--3,000 watts or more--that you can for faster and more accurate readings.
All fish finders have a remote transducer and a readout or display unit. Some remote transducers are meant to be mounted on the boat hull or engine, while others are designed to be cast on a fishing line, then retrieved or left to float and monitor bait.
Mount your fish finder's readout display on a swivel or gimbel; this allows you to view it from any angle and makes it easier for multiple anglers to see the screen.
Don't rely on your fish finder to locate fish. Instead, use it to find underwater structure--where the fish live. It's often up to you to locate the fish from there using your eyes, ears and fishing rod.
Grayline and Grayscale are terms for the fish finder feature that displays how dense objects are in the water. The darker the gray "filling" inside the shape, the more dense it is.
Ignore large, solid schools of baitfish on your fish finder. Instead, look for scattered baitfish--this indicates the predatory fish you're looking for such as bass are active in the area.