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Does Sonar scare fish?

Old 12-23-2005, 03:15 AM
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Default Does Sonar scare fish?

Does Sonar scare fish?

I have received all sorts of opinions from various Guides on this matter - ranging from "absolutely, if you're stopped turn it off" to "absolutely not" ...

I would appreciate your opinions ...
Old 12-23-2005, 04:52 AM
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Default RE: Does Sonar scare fish?

Red-tag sonar, I guess you mean the transducer of a fishfinder does not scare the fish at all simply because they are unable to feel/hear it.I think lowrance or airmar has wrote a nice piece on this on their website.
Old 12-23-2005, 07:08 AM
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Default Re: Does Sonar scare fish?

Well, let's think about this for a minute. I would guess that every single commercial fishing vessel operating out of a developed country (and larger vessels most underdeveloped ones too) is equipped with at least one sonar device, and sometimes a few. If sonar scared fish, these guys would be in big trouble!
Old 12-23-2005, 09:57 AM
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Default Re: Does Sonar scare fish?

As a diver I can tell you there are no weird paterns or whatnot around the boat. Schools of fish swin by constantly and they don't "SPOOK" just because there is sonar running.
Old 12-23-2005, 10:27 AM
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Default Re: Does Sonar scare fish?

From what I understand it is only the powerful low frequency sonar that the Navy uses, and then it only affects mammals, like whales, dolphin, etc. These sonars are much more powerful than anything in the civilian world.

Even the seismic sonar that the oil exploration people use is no where near as powerful, plus remember the commercial that used to be on TV? The one where they towed a seismic oil sonar through a school of fish and they didn't even react to it.


Old 12-23-2005, 02:24 PM
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Default Re: Does Sonar scare fish?

Another excuse for not catching fish - very creative
Old 12-23-2005, 03:15 PM
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Default Re: Does Sonar scare fish?

I'll be honest, I've thought about this and have heard a few reports from some fisherman.

Put your hand under a transducer when it's running, and you can feel the "shock" wave.

I have no idea whether or not they feel anything, but would not be surprised if they did.
Old 12-23-2005, 06:38 PM
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Default Re: Does Sonar scare fish?

Red Rider - 12/23/2005 10:27 AM

From what I understand it is only the powerful low frequency sonar that the Navy uses, and then it only affects mammals, like whales, dolphin, etc. These sonars are much more powerful than anything in the civilian world.
Do you know what frequency and power the Navy uses? What about Submarines?

I'm interested if you know or are just guessing like PETA is. I can say for a fact, there info is INCREDIBLY flawed.
Old 12-23-2005, 09:04 PM
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Default Re: Does Sonar scare fish?

I (had) a 50/200 khz transducer transom mounted to my old RIB. When I was washing the boat, you could tell that it was turned on by the clicking noises you heard when you got near the back of the boat.

Interestingly, Airmar admits (thanks for the heads-up Marti) that humans can hear "transmit pulses" of transducers;

"Can fish hear the sound waves produced by a transducer?"

"No, the sound waves are ultrasonic. They are above (ultra) the sound (sonic) that human ears are able to hear. Humans can hear sound waves from 10 Hz to 20 kHz. Most fish are unable to hear frequencies higher than about 500 Hz to 1 kHz. The ultrasonic sound waves sent out by Airmar transducers have frequencies ranging from 10,000 kHz to 2 Megahertz (200,000,000 Hz), clearly beyond the hearing of fish. However, most people can hear the transmit pulses of our 10 kHz transducers; they sound like a series of clicks."

Firstly is the "10,000kHz" a typo? In context from their statement, did they mean 10Mhz or 1Mhz (1000KHz = 1Mhz)?

Second, what is the difference between "transmit pulses" and sonar signal?

Thirdly, given that Airmar says humans can hear between 10Hz to 20,000Hz, the frequency my 28,000Hz transducer is pretty close to being in range (think logarithmically). Where is the evidence that fish can't hear above 1000Hz?

Now, I am sure that having your sounder on while fishing deep or trolling should have very minimal effect, but what about when you are approaching pelagics feeding on the surface?

Old 12-24-2005, 09:51 PM
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Default Re: Does Sonar scare fish?

I don't know what the frequency is that the Navy uses for their sonar now days. The longest range, most powerful search sonar is very low frequency. The sonar used to find mines and other really small objucts in the water is very high pitched, and is only good for a short range.

From personal experence back in the 70's, I could hear the sonar from some dystroyers/frigates that were about 1 to 5 miles away coming through the hull. It was a ping, just like they always have in the movies. It wasn't really loud, you could hear it, but you had to pay attention. It may be loud when your in a submarine, I don't know, as I have never been in a ship/boat that sank by accident or on purpose.
Old 12-24-2005, 10:19 PM
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Default RE: Does Sonar scare fish?

It certainly is an intriguing question fisherman have wondered about for a long time & I don't have the answer.


I can say that definite fish can be marked anywhere in the water column while fishing, but on the other hand , after building a Heathkit paper graph fishfinder about 30 years ago I plugged it in & held the t/d at arms length( at home) to see if i could hear any output.

As I very slowly moved it closer to my ear, at about 1 ft away I still never heard anything but suddenly felt like a nailgun had shot into my left ear & brain. Completely overwhelming in a not so good way[ Don't try this at home. :-) ] (I know now that it can be very bad for the T/d to try this out of water.) I would think such an effect would reach greater distance in water.

I don't know if t/d basic technology has changed that much since then but always figured there was a good chance that a fish in the beam may feel the strong urge to move away, especially if very close to the t/d. I do leave the 2 F/F's & depth sounder on though and haven't noticed that it has discouraged fish from biting in any way, though they are likely well off the beam when taking a hook.
Old 12-27-2005, 02:16 AM
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Default RE: Does Sonar scare fish?

I've wondered about this, too, and after much reading I've come to some conclusions. I think it's almost certain that fish in general are "aware" of almost any sonar signal that is transmitted through water, though they may not "hear" it in the traditional sense.....much of the sonic info they use to feed and /or flee is derived from the lateral line, in combination with the swim-bladder's resonance...not just the true inner "ears" that fish have. Now whether or not a given specie cares about a given frequency is another story.....I'm sure redfish care very much about the bottlenose dolphin's sonar frequency (whatever it is) and likely work to avoid it. Likewise, the presence of a 200kHz buzz may not matter a bit to a sailfish, but seems to keep menhaden just out of net's range. I think this is the most likely reason people have different experiences with varying sonars and fish species.
Old 12-27-2005, 08:00 AM
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Default Re: Does Sonar scare fish?

Red Rider - 12/24/2005 9:51 PM

I don't know what the frequency is that the Navy uses for their sonar now days. The longest range, most powerful search sonar is very low frequency. The sonar used to find mines and other really small objects in the water is very high pitched, and is only good for a short range.

From personal experience back in the 70's, I could hear the sonar from some dystroyers/frigates that were about 1 to 5 miles away coming through the hull. It was a ping, just like they always have in the movies. It wasn't really loud, you could hear it, but you had to pay attention. It may be loud when your in a submarine, I don't know, as I have never been in a ship/boat that sank by accident or on purpose.
Man,you guys haven't lived until you have been "pinged" by a Navy Vessel! I don't know what frequency their sounders operate on & would be scared to estimate the power but when the ping hits your boat,it resonates all throughout & gets louder & louder until you're abeam of the ship. They probabaly use it as a warning to keep clear of them...I know I always make sure they know I'm not on course that could be interperted as hostile! I would love to see the picture they get on their scopes;you can probably count the scales on the fish with the Navy's technology!
Old 12-27-2005, 10:56 AM
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Default Re: Does Sonar scare fish?

Greetings all! Since there are approximately 25,000 species of fish then I would say that there are approximately 25,000 different answers to this question. Across this range of species there is a great variety and complexity to the organs that sense sound and vibration.

So yes, absolutely, fish hear sound but not all fishes hear the same sounds. Much research is being done to help answer these questions. Check out http://www.life.umd.edu/biology/popperlab/index.htm

There are theories that some prey species are sensitive to the sounds created by marine mammals that rely on echo-location to find food. These fish go into hiding as a response to certain clicks and pings.

If you are really seroius about educating yourself in the biology or fishes there is a class starting next month,... it is taught at the New England Aquarium (in Boston). Check out the course description at http://www.brandeis.edu/marinestudies/fishes.html

All the best! E Fitz.

Old 12-27-2005, 11:18 AM
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Default Re: Does Sonar scare fish?

OK, 99.99999% of the time, Submarines transmit NOTHING on Sonar. The 726 Ohio class submarine CAN'T transmit. They purposely left it out. It was cheaper and one less thing that could accidently give away their position. I have been on Subs for 18 years and other than testing pierside, in local op areas during traing or around Andros Island doing sound testing, I have never heard of a sub going "Active" and transmitting. Too many movies.

Unfortunately frequencies and power is somewhat classified for Submarines. It also NO longer sounds like the movies, it is more akin to a bird chirp or a macaw sqwauk.

I'll look up the surface ship stuff and let you know, I have no idea. Yes they are loud, but I haven't been on a Fast Attack in 8 years and NO ONE pings a Boomer.

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