Lower frequency transducers, with longer waves and fewer waves per second, show less detail (larger fish) but carry more energy and penetrate to greater depths. One sound wave at 50kHz is slightly larger than 1", so a 50kHz sound wave will only detect fish if their air bladders are large, slightly longer than an inch. Lower frequency won’t provide as clear of a picture but will operate effectively in the depths of the ocean or Lake Michigan.
Fishfinders operate using a single frequency transducer, dual frequencies, multiple frequencies or a broadband CHIRP system. In general, higher frequencies give the finest detail resolution, the least background noise on your screen and the best view from a fast-moving boat, but don’t penetrate as deeply as lower frequencies. Shallow-water inland anglers generally choose higher frequencies of 200kHz, 400kHz or 800kHz. For maximum depth, use lower frequencies. We recommend 200kHz or higher (up to 800kHz) for water depths up to 200' and 80kHz or 50kHz for deeper waters.
When checking the transducer, the most important feature is the cone angle. For a bigger perspective of the verges underneath, choose a bigger degree on the cone. The wider beam gives more coverage of the under water and allows locating more fish within it. However, its drawback is the quick loss of strength. Due to this, it cannot penetrate the water as deep as the narrow cone. The narrow one can go really deep even in shallow waters and can also give information on the composition of the bottom.
The swivel sinker is similar to the plain one, except that instead of loops, there are swivels on each end to attach the line. This is a decided improvement, as it prevents the line from twisting and tangling. In trolling, swivel sinkers are indispensable. The slide sinker, for bottom fishing, is a leaden tube which allows the line to slip through it, when the fish bites. This is an excellent arrangement, as the angler can feel the smallest bite, whereas in the other case the fish must first move the sinker before the angler feels him.
The image to the right shows a school of white bass aggressively feeding on a school of threadfin shad. Note the school of baitfish near the bottom. When threatened, baitfish form a tightly packed school, as the individuals seek safety in the center of the school. This typically looks like an irregularly shaped ball or thumbprint on the fishfinder screen. When no predators are nearby, a school of baitfish frequently appears as a thin horizontal line across the screen, at the depth where the temperature and oxygen levels are optimal. The nearly-vertical lines near the right edge of the screen show the path of fishing lures falling to the bottom.
Higher frequencies, such as 192 or 200, are ideal for fishing in shallow water. Lower frequencies, such as 50 or 83, are perfect for deep water fishing. To find the top fish finder for the money, knowing what area you’re planning on using it in will lead to more catches. Remember that the higher the frequency, the more detail you’ll have on the screen.
This unit has a colorful and compact 3.5 inch color screen that is fully equipped with a Garmin high-sensitivity GPS and Garmin’s very own Sonar, which uses Garmin CHIRP ClearVu Scanning. This GPS gives you the ability to mark your favorite hotspots and fishing areas, docks, and slipways, while using high-speed data technology to display any information that you may need, immediately on the screen.
While not every object will be as easy to distinguish, you can always get clues from the shape and also the strength of the sonar return. Notice the multiple orange sonar returns underneath the car – these tell you that this is a very hard object. The sonar scans have hit the car, bounced up to the surface of the water, bounced off the surface and hit the car again.
Fishing traps are culturally almost universal and seem to have been independently invented many times. There are essentially two types of trap, a permanent or semi-permanent structure placed in a river or tidal area and pot-traps that are baited to attract prey and periodically lifted. They might have the form of a fishing weir or a lobster trap. A typical trap can have a frame of thick steel wire in the shape of a heart, with chicken wire stretched around it. The mesh wraps around the frame and then tapers into the inside of the trap. When a fish swims inside through this opening, it cannot get out, as the chicken wire opening bends back into its original narrowness. In earlier times, traps were constructed of wood and fibre.
In operation, an electrical impulse from a transmitter is converted into a sound wave by an underwater transducer, called a hydrophone, and sent into the water. When the wave strikes something such as a fish, it is reflected back and displays size, composition, and shape of the object. The exact extent of what can be discerned depends on the frequency and power of the pulse transmitted. Knowing the speed of the wave in the water, the distance to the object that reflected the wave can be determined. The speed of sound through the water column depends on the temperature, salinity and pressure (depth). This is approximately c = 1404.85 + 4.618T - 0.0523T2 + 1.25S + 0.017D (where c = sound speed (m/s), T = temperature (degrees Celsius), S = salinity (per mille) and D = depth). Typical values used by commercial fish finders are 4921 ft/s (1500 m/s) in seawater and 4800 ft/s (1463 m/s) in freshwater.
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The term tackle, with the meaning "apparatus for fishing", has been in use from 1398 AD. Fishing tackle is also called fishing gear. However the term fishing gear is more usually used in the context of commercial fishing, whereas fishing tackle is more often used in the context of recreational fishing. This article covers equipment used by recreational anglers.