Sounds, noises, play a huge part in human relationships with the world. Our fear filled reaction to sharp violent sounds, reflects our fear of violence. But does this human fear exist in fish?
Aeons of fear of sharp sounds is etched deep in our genes. For humans, things that go bump in the night are the fuel of fear. Despite this we remain fascinated by fear. TV and film is littered with this fascination. Maybe our fascination with fear, is some kind of 'training'. When humans are frightened they go into a starkly simplistic mode, which selects fight, flight or submission.
But in the sea, the relationship between predator and prey is even more simplistic. For most prey the choice is flight, flight or flight.
For predator fish, the notion of what is noise, is vastly different from ours. It may well be that noise, commotion, the unusual, is a key to survival. Predator fish may be forced to investigate all noise to check whether the noise means food.
How we exploit this concept of noise may determine our success as fishermen.
There are some fishermen that take extraordinary measures to reduce noise in a boat. I know more than a few who will not even allow a radio on the boat, in case the noise is transmitted through the hull, into the water. A boat hull is basically a giant drum. Any noise in the boat is quickly, and very efficiently transferred into the water, where it can travel large distances.
Sound travels much better, and further, in water than air.
Those who dive will be aware how loud the noise of a passing boat can be. Divers who have been lucky enough to dive near dolphins or whales will know the sensation of both the sound of their 'calls', and the tingling feel of their sonar signals.
Many years ago I worked briefly on a prawn boat out of Coolangata in northern New South Wales. We had the benefit of (then) sophisticated sonar equipment. But when the prawns rose off the bottom at night the sonar would immediately go into a spasm. The 'noise' made by millions of legs and tails scraping together, blew the signal processing software inside the sonar apart.
It was not until we turned down the discrimination knobs up to nearly off the scale, which meant only one signal in thousands was being processed, could we get an accurate depth reading of the prawns.
Some skippers swore that you could hear the noise of prawn schools through steel hulls, and even better through aluminium hulls.
Until the prawns rose from the bottom, the sea bed would often be lifeless. No signs of fish. But in a very short time after a prawn school rose, the sonar screen around it would be splattered with fish.
I enjoy fishing estuaries on a quiet, still evening. Drifting slowly along, pushed by the incoming tide, picking up a few fish with a drifting bait, is a quiet pleasure.
Well I thought it was quiet until I heard a recording of the underwater noise as the water covered the tidal flats. Down there it is a constant cacophony of sound. The scraping of crabs legs, is as clear and sharp as the scream of chalk on a blackboard. The sounds of empty shells being rolled along the bottom by the incoming tide, was like Jaffas rolled down the cinema floor from the back rows.
The recording equipment could convert pressure waves into 'sounds' audible to the human ear. We could plainly hear the whoosh of shellfish expelling water.
Here are three pieces in the noise puzzle.
The first piece concerns young Ed the lad. During the early teen years Ed was downright clumsy. I put it down to the fact that his body was growing so fast, his nervous system could not catch up. Messages were taking too long to travel from his brain to his limbs.
Fishing in the tiny 'tinny' (Kiwi speak for an aluminium dinghy) Ed set new levels of noise pollution for the surrounding area. Once I swear I saw the periscope of a submarine pop up to investigate the noise that had shut down it's sonar system. Maybe they thought a small war had broken out.
When we reached a fishing spot, the normal course of noisy events was well rehearsed. Ed would pick up the anchor and chain, and promptly drop it on the bottom of the boat. He would pick it up again, and toss it over the side, allowing the chain to bounce and rattle off the front coming.
Then Ed would pick up the tackle box, drop it, pick it up again, and drop it onto the aluminium side seats. Rigging up became the signal to drop sinkers and knives onto the bottom of the boat.
Only those who have fished from tinnys know the extraordinary ability of these aluminium boats to transmit sound.
Eventually Ed would fire out a bait, into water still rippling with the sonic aftermath of all this noise. Often, too often for the conventional rule of being quiet in a boat to be universally true, he would immediately hook up.
The second piece of the noise puzzle is provided by Mark Kitteridge fishing devotee and writer, who worked with me at my tackle shop. When the boat reaches 'the spot' you would have to move at the speed of light to get a bait or jig into the water ahead of Mr. Kitteridge. The anchor crashes down, and so does Mark's bait, almost simultaneously. Too often for other fishermen's egos, Mark hooks up almost immediately.
The third piece is provided by a number of good and better kingfish fishermen. These guys motor up to the spot at full throttle, and then execute a series of figure eights in the general area. One of these blokes has a bag full of hard stones. As soon as the boat stops he dangles the bag over the side, and vigorously shakes it up and down. Divers chasing kingis used to bang a knife on their dive tanks to attract kingis. The clanking noise of the hard stones is similar.
The noise and commotion attracts kingis around too often for it to be a case of the kingis arriving despite the noise.
Also, and again, happening too often to ignore, is the number of big snapper that grab a live bait intended for kingis, amongst all the noise and commotion.
On the very rare occasions that I have been able to see snapper in a berley trail, I have been fascinated that every time a fish is hooked up, the other fish get excited, and dash about grabbing everything in the water.
It seems as if the struggles, the 'noise', of the hooked fish are read as just that, the struggles of a wounded fish. There appears to be no kinship amongst fish. The fact that it is another snapper that is in trouble, does not seem to deter its kin. A struggling fish, any fish, friend or foe, seems to spell food.
More often I have seen kingis in the berley trail totally uninterested in a live bait which is in their and my plain sight. Throw a 'popper' (cup or slanted face tube lure that splashes as it is pulled across the surface) in the water, and stir things up a bit, and off goes the live bait. Sometimes a rod tip slashed through the water in figure eights does the same trick.
The problem of kingis being uninterested in a live bait, seems to be more pronounced, if the live bait has been in the water for some time, before the kingis turned up. Throw a fresh live bait into the water, after the kingis turn up, and the bait boredom factor is much less in evidence.
It is my guess that the first signal to a predator that a food fish is in trouble, is the unusual frantic 'noise' of its movements.
The violence of panic, signals the ultimate act of violence.
The most responsive sense for a fish is not sight, or smell, it is 'feel'. But again it is not 'feel' in the human sense. Down each side of a fishes body is a line of receptors that can detect amazingly low levels of sonic, and other pressure wave disturbances in the water. These receptors can detect pressure waves caused by other fish swimming, sound waves, and other underwater disturbances.
In predator fish the ability to detect this underwater noise, and locate the source, is a prime factor in successful food detection. This 'noise' is 'heard' long before any sight of food is picked up.
It may well be that predator fish find the bulk of their food by homing in on 'sounds' that indicate disturbances. These 'sounds' may be the frantic movements of bait fish being harried by other predator fish. Noise, as we know it, may be an ally, rather than an enemy.
To paraphrase Dr McCoy, on the Star Ship Enterprise, "It's noise Jim, but not as we know it."
Article written by Tony Bishop
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