How to sneak up on and not spookthe fish is a topic full of controversy, and sadly lacking cold, hard facts. It came up the other day when we were wreck fishing, and I revved the engine while repositioning the boat. My nine-year-old son chastised me, for probably spooking all of the fish within a mile – and he may have been right to do so!
Luckily, I do have some data on this topic because I took underwater sound measurements a few years back, while researching an article. Here’s what I discovered.
1. All motors, even electrics, create noise. Most of it comes from the spinning prop, and the sound level is directly relative to prop speed – the faster it spins, the more of a whine it produces under water. Electrics produce the least amount of engine noise, then four-strokes, and then two-strokes. For inboards, gas and gas I/Os make a higher pitch noise then diesels, but both make about the same amount of volume.
2. Two-stroke motors make a real racket when in neutral. When approaching a hotspot, shut the motor down while it’s still in gear and drift into the area, to avoid making this noise.
3. Push-poles are not at all silent. In fact, on shell and rock bottoms they make more noise then an electric outboard. On sand and mud, however, they’re the quietest approach.
4. Dragging a tacklebox across a fiberglass deck, dropping a hatch, and other actions that make noise against the boat transmit right into the water. Slamming a hatch that doesn’t have a rubber gasket on it sounds like a gunshot, from 50′ away under water.
5. Voices carry under water, too. Just under the water’s surface, it’s possible to hear someone talking from 50′ away.
So, did I spook the fish when I revved up the other day? In retrospect, I think probably so… but don’t tell Max or I’ll never hear the end of it!