Catching Bigger Fish Using Sonar

The sonar display began to show a wave of spaghetti and meatballs, a mix of wiggly looking worms and clouds down toward the sea floor. This was to be the first time I’d returned to fish the spot since detecting a tiny bit of life on sonar while traveling home one trip at 25 knots. The location was marked and needed investigation- today was that day.


Approaching that mark super slowly allowed lots of information to come flooding in by sonar. The range was manually adjusted to suit the water depth, a split-screen using zoom was also utilised and the sensitivity adjusted to provide a crisp image. I opted to drive over the mark heading into the tide to slow the vessel even more to obtain uncompressed data. As the vessel neared the mark a show of smooth tailed trevally and yakka appeared, they were sitting on the back side of the current that was obviously running over some kind of structure, most likley another wonky hole. Predators would be in front, and they were, an eye-popping school of nannygai and red emperor, the fish averaging around 10 kilos.

A typical school of 8-10 kg large-mouth nannygai and their corresponding sonar image.

By knowing the 200 kHz frequency on the 2D tradition sonar would show around 11 metres of sea floor in this case, it enabled the on-screen data to be processed so the boat could be positioned properly. Too many anglers get this bit wrong and end up fishing 10 to 50m from the required target position as the tide and wind has its affect- quickly. The detection area and the return signals showed the fish now just behind the vessel as there were faint returns showing on display. This meant the fish were only just in the sonar cone on the edge of the 11 metre detection area, so I drifted back about 2 metres, then spot-locked the electric motor so the 1 ounce jig head on the soft plastic lure could be cast upstream and eventually wash down with the tide and reach the target area just before it hit the bottom. It hit the target area and with just a few hops of the worm-like lure a large red Emperor pounced and the rest is history.

Tuning your unit is critical, driving in a controlled manner helps with detailed images appearing on the screen.

Background knowledge on the species helps a truck load. Having real-time knowledge on how each species move and school underwater is very helpful when trying to identify targets on display.

Sonars are cool tools and getting active tuning the unit to each specific location is an art, but the results are worth every effort. In just that one trip $120.00 in fuel was burnt. The price of $299.00 for the sonar course is cheap considering the years ahead that an angler can utilise the information and therefore process data in a better way and catch more fish because of ‘Knowing versus Guessing!’

We also have a sonar forum available to course subscribers to further discuss and learn about sonar.

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