Foo showing off a clown featherback; his black fish finder is seen attached to his kayak near his knee.
STRIKE a metallic object, and you’ll hear a sharp clang. Knock on wood, and you get a dull thunk. It’s the basic principle behind sonar – sound waves reflecting off different objects.
Anglers use sonar technology, too, in the form of a fish finder, which emits ultrasonic pulses into the water and “listens” to the echoes bouncing off objects below.
At the heart of a fish finder is the transducer, which sends out ultrasonic sound waves that bounce off objects like fish, the lakebed, or underwater structures. The transducer then converts these echoes, which the fish finder processes to display a visual representation of what’s beneath the surface.
When you fit a fish finder to your fishing kayak, you can expect even better results.
Seasoned angler Ben Foo explains that since a kayak moves slowly, the fish finder’s transducer has more time to pick up sonar echoes and generate a highly accurate picture of what lies below.
“But it can be too accurate sometimes. If you’re using a fish finder on a kayak, especially on a lake, it’s important to reduce the sensitivity,” he advised.
Just nice; this fish finder’s settings allow it to show clear water from the kayak to the lake bed (red), with some underwater vegetation (blue) at the bottom.
Most fish finders come with a factory-set sensitivity of 75%, but Foo suggests lowering it to around 65% or less.
“Do this until the fuzzy and unwanted stuff on the screen clears up or becomes less visible,” he added.
Another key aspect of sonar technology is that the ultrasonic pulses form a cone shape – narrow from your vessel and widening as they travel downwards.
“If the water is just a few metres deep, the cone will be small, so the image on your screen may show only a 2-metre radius around your kayak. You need to interpret that carefully,” Foo said.
For kayak fishing, Foo recommends a basic fish finder priced between RM1,000 and RM2,000. It can do more than just read the bottom of the water.
“When you catch a fish, press a button on the fish finder, and it will record the exact location,” he added.
The device can also map the underwater landscape, track your movement, and when you return home, you can review your trip by inserting the memory card into your computer.
Too sensitive; this fish finder’s settings caused it to read all manner of suspended algae and detritus less than 2m below the kayak as objects.
There’s a reason it’s called a fish finder – it really does help locate fish. But again, adjusting the settings is crucial.
Mat Ngunjun, a Penang-based angler who mainly fishes at sea on a kayak, sets his fish finder to sound an alert only for fish weighing more than 1kg.
“Otherwise, it will beep frantically even for small scads (selar), and I’ll be glued to the screen instead of focusing on fishing,” he said.
He and his kayak-fishing buddies have grown dependent on their fish finders, and recalled watching a friend kayak near the shore when his fish finder detected a 5m depression below, possibly hiding a large fish. His friend dropped a jig and reeled in a 7kg grouper.
But Mat warns that relying too heavily on a fish finder can leave you “mati kutu” (a Malay idiom meaning helpless) if it breaks down.
“You depend on it so much that you lose the ability to read the water, the currents, the tides,” he said.
Vincent Paul, a kayak-fisher from Ipoh who specialises in fishing ex-mining lakes, primarily uses his fish finder to read depths and water temperature – key factors in determining whether a spot is promising.
“In lakes, there can be a lot of underwater vegetation, which creates confusing ‘noise’ on the screen.
“I want to see structures like sunken trees or mounds, where predatory fish hide to ambush prey. That’s where I cast my lures to entice them,” he explained.
