Sounding out those Dam Fish

Being safe in the knowledge that there are plenty of fish in our freshwater lakes is not a guarantee of finding and catching them. While we can readily see what is above the water there is no way of knowing what is under the water. Depth sounders, echo sounders, fish finders, call them what you like, are basically a sonar system that sends out high frequency radio signals that hit the bottom and other objects and bounce back to the unit which are then put on a screen. They are a vital part of successful impoundment fishing. By using these electronic aids, anglers can firstly know how deep the water is and then look for suitable fish holding structure and finally find fish themselves.
Many sounders have fish ID systems that will put fish symbols on the screen to represent fish. While this makes the system easy to use, many objects such as weed and thermoclines can show up as fish or "phantoms". A far better way to find fish is to turn the fish ID setting off and use raw sonar instead. In raw sonar, fish will show up as arches or slashes on the screen with schools of baitfish showing up as large balls, thus eliminating the phantoms. (See picture)
Sounders are readily available at tackle stores and marine outlets. They can cost as little as a couple of hundred dollars to over a thousand dollars. A general rule of thumb is you get what you pay for. One of the main things to look for in any sounder is the vertical pixel (small dots that make up the screen) count. The more pixels on the screen, the more detailed information can be given. A high pixel count can mean the difference between finding fish and not.
While the cost of a sounder may scare many away from purchasing one, they are an investment that should last for many years with a little care.

Garry Fitzgerald.