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Catching up with fish
What can we learn from this Fish Finder screen?
This screenshot was taken while the boat was drifting at a speed of 0.5 knots. The Fish Finder was set to transmit at 200 kHz.
Today's target was the Japanese horse mackerel. They form fish school when swimming around, and inhabit rocky area where the sea current goes through.
Let’s see how to look at the Fish Finder screen. Since the boat was in very slow motion, the echo of seabed is kept almost flat. (Reference: Fish school display during mooring and brief stops) Bottom trail on the left half of the screen is comparably longer than that of the right half, which makes it easier for you to guess that this is a rocky area. But if you assumed the seabed on the right half is a sandy area because the trail on the right half of the screen is shorter and the structure is flatter, that is unfortunately a misinterpretation.
Let's take a close look at the color of the echo which indicates the strength of the reflected ultrasonic wave. While the color is red on the left half, it is brown red on the right half. This means the strength of the reflected ultrasonic wave is higher on the right.
We set our game field on which the left side of the screen shows, and ended up not only catching the Japanese horse mackerel around the rock but also the half-lined cardinal which were swimming below the fish school of Japanese horse mackerel. Although it looked like a single fish school echo on the screen, it was actually composed of two kinds of fish school, the Japanese horse mackerel and a half-lined cardinal.
Underwater shot shown below was taken at another point, but it shows same sea strata configuration as when we caught the half-lined cardinal. You can see fish school of the Japanese horse mackerel on upper part and you can see the half-line cardinal below them.
Also the Japanese horse mackerel do not stay in a same location for long time. They usually swim around a few meters away from the rock. Therefore, it got much easier for us to catch them after the fish move out to the flatter area from rocky area which inhabited by many other kind of fish.
DAIWA field tester, Writer at Boat Club, a monthly Japanese boating publication
Nobuaki is a hobby angler who travels around Japan together with his beloved car-top boat Tomoe-maru. With a keen interest in fishing as well as scuba diving, he has gained a substantial amount of knowledge in how to utilize fish finders to the fullest. Nobuaki regularly holds well-attended training courses in the use of fish finders, as well as being a proponent for proper sea manners and safety at sea. Sharing his knowledge is a passion for Nobuaki, and he manages his own homepage as well as being a sought after writer in Japanese boating publications.