Boat Noise

The relationship between saltwater fish and underwater noise is complicated.

Some fish spook easier than others and, depending on location and water depth, other fish are actually attracted to sound. Knowing the difference can go a long way toward a successful day of fishing.

Tripletail, for example, are on the shy side. I learned this the hard way after spotting several in the waves, turned the boat around and tried to approach from downwind.  They were completely spooked by waves slapping under the bow, and wisely disappeared. Ideally we would have had calm water and an electric motor, to stalk tasty tripletail. Once they spook into the depths, they’re gone for good.

At the opposite end of the spectrum: when we first started fishing for ling, we always heard you should slap the water with a paddle, circle the oil rig, gun the motor in neutral, and generally put up a ruckus that would attract these curious fish. And it sometimes worked, though I’m not so sure today, when a much smaller population of ling may have learned to avoid boat noise. As we observed while diving the rigs for many years, they don’t seem to mind rig-noise, with that loud airhorn sounding off every 20-30 seconds some five stories above. That noise punishes fishermen more than fish.

Further out in the open Gulf with a vast expanses of quiet, blue water, boat noise actually attracts pelagic fish. How else to explain the many years of angler success at trolling up marlin, sailfish, mahi, wahoo and tuna? Some boats are said to be better fish attractors than others, because each has its own engine and hull vibration.

Opposite of that, I think shallow water bay fish are the most noise-wary. Burning a shoreline with the boat will send fish sprinting up to 100 yards out in the bay; they won’t put up with that. That’s why you see the silent poling with a long stick like skiff guides use, especially for ultra-wary bonefish. A long pole has many advantages, and their silence (if you can avoid thumping the gunnel) is often the key to a great day on the water. 

The following observations are from years of noticing the affects of sound on various species of fish and their habitats. There are all sorts of ways of sneaking up on noise-wary fish, including wading, walking the jetties, surf fishing, kayaking, electric motors, or tying the boat to offshore oil rigs and sitting quiet.

I’ve fished several boathouses on the bays either with or without a howling diesel generator, and certainly did better without the noise, at least during daylight hours. (Plenty of slot-sized redfish). Where it was quiet enough to hear sheepshead tugging and splashing beneath the planks. At night with lights attracting, the fish behave differently, with smaller trout and ladyfish content to put up with the noise and vibration, as long as passing, tasty baitfish and shrimp do the same.

Walking the jetties is about as quiet as it gets, either by hiking from shore or anchoring the boat and climbing onto the rocks, which we did for countless summer afternoons. Sometimes we even anchored the boat and swam to the rocks when waves and wind weren’t right. In that regard we were true jetty rats. Those trout and redfish and countless sheepshead had no clue we were standing right over them, watching them swim by. We could walk and sling spoons all day, and the fish never heard a sound from us, not even a landing net. Those fish weren’t exactly gun-shy, since they put up with daily ship and boat traffic. They were quite the opposite of tailing redfish or trophy trout in some placid, backwater pond in the salt marsh.

As mentioned, wave slap on a boat hull can be a problem. Big trout on expansive, open flats can somehow detect a boat quietly drifting sideways or being poled. Near South Padre Island, drifting in a light breeze, we’d spot big trout leaving the scene some 50 yards downwind, pushing a v-wake like a shark, another sow trout headed for deeper water. It was frustrating, too. We finally caught one on a long cast, a 28-inch sow soon released. You can bet those big trout haven’t survived for so long, dodging boats and hooks for what, ten years without learning a few smarts. A trout of 28 inches takes ten years to grow that big, according to the TP&W growth chart.

In the bays I still anchor the boat manually, often by the stern, which is more work than the boats with stern-mounted Power Poles. I may have the quieter edge in wave-slap noise, because a boat bobs and tilts when anchored, while power poles hold each boat more rigidly. Maybe those two techniques are too close to matter, noise-wise, and only a big trout could tell us, if only they could talk. With an anchor in the wind, sometimes I get a little water over the transom, and a salty splash on the stern reels, preferably avoided when possible. My favorite trick, mentioned here before, is to park snug against a high-tide shoreline, anchored amidships. Or by the bow and stern with two anchors, if wind and current are a problem. That way we can fire a broadside of baits and spoons way out there, with zero boat noise. We’ve found that 8-foot spin rods are ideal; they throw farther and never really backlash. You need only one ounce of lead to deliver a bait a long ways, when using 12-pound line. The boat sits quiet as a church mouse, and those fish 30-35 yards away, once again, have no clue. Several times, I’ve tried anchoring out from shore there, to shorten our casts, but we never got a bite.

Not sure about electric motors or their pitch of sound, (probably high) but some fish might be wary of it. I know low-frequency sound carries in the water as a distress signal, like a croaker or pigfish will make. Sharks are certainly attracted to low frequency vibrations, even explosions. (Bad news for many during WWII).

Some of today’s bay boats have expensive sound systems with thumping bass, and I’m not sure how that affects their catches. Surely the fish hear it; that thumping carries a long ways. I don’t play loud music while fishing shallow bays, not even ACDC that has became so popular with the big POC boats, audible for a half mile. Yes, we all miss Bon Scott, but most of us prefer quiet on the bays while escaping stress back on shore.  

Slamming boat lids in the boat is a no-no, of course. Even offshore, I couldn’t tolerate that uncalled-for noise when we were anchored and fishing for tournament kingfish. Many kings are caught while trolling, but about 90 percent of our tournament winners happened while the boat was anchored silent or tied to an oil rig. Not trolling. Big kings are not exactly ocean wanderers, they live on the coastal shelf where boat traffic is more common. From 10 to 15 years and older, big kings have seen plenty of hooks and boats.

A few final tips: think about the extra noise, when shifting gears. I was snorkeling inside a rig one day and another boat approached to tie up. Every time they shifted gears, hundreds of fish inside the rig within 20 feet of the surface would all bolt several feet, before settling down again. The noise was very distinct, a loud “clunk” over the engine noise. To this day, that’s why I never shift gear when approaching a honeyhole; instead I cut the motor while still in forward gear and coast in to anchor. Preferably from upwind, though that’s not always possible.

I’ve also shortened my anchor chain to three feet, for less rattle on the gunnel. You don’t need six feet of chain when fishing shallow water. I drive from the back of the boat, so anchoring by the stern saves me from climbing over people to drop the bow anchor. Another advantage: Unseasoned anglers have been known to rattle the anchor chain something terrible. Or worse, heave the anchor out there with a hearty splash, making me wince. I’m thinking stealth, while they’re thinking, Heave ho, me hearties!