Furuno FSV-30, Operator'S Manual

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3. VERTICAL MODE
3-18
3.13 Application to Bonito and Tuna Fishing
Tracking of bonito and tuna presents a special challenge to the sonar operator:
He must try to keep them within the sonar beam, a formidable task considering
their high speed and penchant for leaping and diving. The FSV-30, however, with
its vertical beam, makes this task easier.
3.13.1 Searching
Neither the naked eye nor binoculars can continually track fish schools which
make lightning quick runs between the surface and midwater. A sonar, however,
provides a continuous view of several hundred meters of sea area around the
boat, both at the surface and below it.
3.13.2 Tracking
If you are visually tracking a fish school which characteristically leaps and dives
regularly, or a school with a flock of birds hovering over it, the school will scatter
once the vessel approaches, thus you will lose sight of the school. This sonar
provides continuous pictures of underwater conditions, so you can always know
where a fish school is. For tracking the schools which leap and dive often the
vertical mode is especially effective.
Tracking