As a rule I've found back country trout more wary of wading than the frauds we throw at them, while the opposite is true of pressured waters.
Hmmmm... Interesting. I'll have to keep that in mind next time I'm up there. Something to play around with.
I'd say shallow trout, away from sanctuary, are spooky -period. So...small streams tend to be full of spooky trout.
On pressured water (or anywhere) fish moving up to feed in skinny head riffs, or stream banks, are also VERY spooky. Add flat water and they can be almost impossible to approach.
But the deeper areas, out of sight, I suppose, can be approached easier -esp if there's some broken water to help mask movement, sound, and especially pressure waves.
Most animals have several alarm sensors: usually sight, scent, sound, touch. which exist in a hierarchical arrangement of importance that varies by species, prior sensitization/state of alarm, and existing environmental conditions. For many creatures/circumstances, only one alarm need be tripped to send them fleeing. But other times the stimulus may require further assessment, bc running away devours energy. In unspooked whitetail deer for instance, an out of place sound or image will most often cause them to freeze to gain further info. Often it takes two senses, the ears and eyes, to maker a decision. As a predator, it’s easier to get away with tripping one sensor on your prey, but not two. With deer though, the nose trumps all. Mule deer are more visual than whitetails, being much quicker to trust their eyes.
Fish have multiple alarm sensors too, and a hierarchical arrangement of importance too. However, fish have an expanded tactile system via hair cells (lateral line is part of this system), and some have electro-receptive capabilities –the ability to detect slight changes in electric fields. So, when throwing flies to electroreceptive bullheads and catfish we are simply speaking the wrong language, although channel cats are much more visual and more apt to be duped by artificials.
For carp it’s hearing/touch, taste/smell, and sight in that order. As ostariophysids (like other minnows), they contain “Weberian ossicles”, bony structures attached to the inner ears which amplify sound. I found, in fly-fishing for them, that the sound of a leader or tippet “singing” in the water (produced in a rapid pick-up, or current over a sunken line) would put pods of carp down instantly. I’ve not seen this degree of sound sensitivity in any other fish.
For trout (and bass) I’d say it’s pressure waves, sound, then sight, for predator detection. But, when trout are vulnerable –shallow fish –tripping any one sense can cause them to flee. Scent is known to cause a powerful flight response in pacific salmon. They are sensitive to the scent of seals at amazingly minute concentrations. At one time a study isolated the amino acid L-Serine was showed to elicit fright reactions in fish. In-Fisherman magazine jumper on it and tested the palm secretions of its staff, and lo and behold Al Lindner was found to have one of the lowest L-Serine concentrations known! No wonder he catches SO many fish, eh? Over time though the original research was dis-credited, which leaves one to speculate whether L-Serine concentrations in human palm secretions aren’t a better indicator of ego than anything else.
I’ve come to realize just how sensitive shallow fish can be, in one instance by playing with a pod of trout in an outflow culvert of a hatchery I worked at, that contained some escapee's. The idea was to see how close I could approach. Seems easy enough. However, the area was surrounded by soggy ground -that carries sound/pressure waves remarkably easily. I could never get close., as the trout could feel the pressure wake created as my feet depressed the soft ground. The same is true along soggy pond edges; Try to approach shoreline hugging bluegills without them noticing! After the ground dries, it's much easier, and it’s their eyes especially you have to avoid.
Something that feels similar occurs when I’m hunting deer (or rabbits) on moist ground; Foot falls reverberate, esp if you kick a rock or root, and the sound carries; I swear it’s "felt", in the diaphragm. Deer and rabbits communicate by ground-thumping with hind feet, and it produces a low frequency “thump” I can feel in my diaphragm or in my gut. Grouse wings can do the same thing. Maybe it’s my adrenals (located on my kidneys) activating, but I always believed I could feel it. Regardless of origin, I’ve become sensitized to it. And when I feel it, I freeze.
Well… This one got me going. Welcome to my world ... where do fish stop and other critters begin?? Hope all this is at least interesting if not actually useful.