Salmon ears, Sound and vibration in water, Fish Communication and Noisy noises

and a whole bunch of other really cool/interesting/thought-provoking/andjustplaingoodreading fishy-science facts from MCX Fisher via buddy Pete Tyjas’ always great Eat Sleep Fish ezine.

even if the only image in the article appears to be a cod,

codsalmon
based on Atlantic salmon research, MCX goes a stretch further on explaining and going into great detail (and be sure to follow the adjoing links !*) on, eh, there’s no way i can add any more info on this subject so here’s a few excerpts:
“The underwater sound environment is entirely different to that in which we live in air. Accordingly, when thinking about the underwater world we have to dump our experience and preconceptions. Simply, salmon don’t ‘hear’ like us, because they don’t have ears”

“The key features of sound in water are that it:
– Is about 800 times more intense than in air, because the water is incompressible and therefore a much more efficient transmitter. In addition the surface layer reflects sound back into the water.
-Travels far further than in air: relatively minor events are detectable at ranges measured in kilometres, but the level of background noise is relatively very high because it is drawn from a much wider area.
-Goes about 4.4 times faster.
-Is influenced by the composition of the water.”

So much, so interesting, but what is its relevance to the angler?
If certain frequencies can stimulate a salmon to attack oceanic prey, can we exploit this in fresh water? In thinking about this it helps to grasp what 300 Hz sounds like in air : for comparison Middle C is 261 Hz. It is certainly much higher than the dull thrum of commonplace line vibration in fast water, which is in the range 10-30 Hz.”

and lastly,
“The moment you step into a pool the salmon’s formidable sensors will detect your activity, even if you have felt soles and a light step. However, they don’t know it’s you or what you’re doing, because in evolutionary terms humans haven’t been angling long enough to achieve any genetic impact on salmon. Unlike the calls of whales, seals and other fish, salmon anglers’ noises aren’t in the salmon signal library. Certainly they wouldn’t be able to connect the crunch of your studs on the gravel and the clink of your wading staff on the rocks with the drama of being caught, except perhaps if they’d been caught shortly before by another heavy-footed fisherman.”

but there’s a gazillion more fascinating things to read on this noisy subject and to do so simply click the cod ! enjoy !


* and one of those happens to be a really geeky but eversocool Beeps, Chirps and Noise channel on youtube where i found this little brown noise treat ! (yeah, that’s sounds a little idon’tknowwhat but don’t be afraid, you won’t have to go clean up after listening to it… )

“Brown noise is noise with a power spectral density inversely proportional to the frequency squared. It decreases in power by 6 dB per octave or 20 dB per decade. The sound of brown noise mimics a waterfall or heavy rainfall.”

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