Three Main Trout Senses
An angler should therefore become familiar with the three main senses a trout uses. These are:
Trout have amazing powers of smell. For humans, trying to understand smell underwater is rather difficult since we can't do it. However, trout have no difficulty smelling underwater, so it is worth an anglers time to make sure that they aren't introducing foreign smells into a trout stream (which can warn a trout to a lurking danger such as a fisherman.)
When fly fishing for trout, do your best to avoid any artificial smells that are completely foreign to a trout stream. Avoiding these smells, though, of often easier said than done, as the sources of these smells can come from many sources. Fly line cleaners, fly floatants, epoxies and glue can all contribute alien smells to a trout stream. Other things such as aftershave, deodorant and even the smell of your clothing can all tip off a trout that an angler is near.
Obviously, you can't get rid of all foreign smells you may introduce into a trout stream. However, there are a number of easy things a fisherman can do to reduce the likelihood of a trout getting wise due to smell. When using fly line cleaners and fly floatants, use the newer ones that are designed to 'mask' the chemical smell. The cleaners and floatants are usually the same price as other 'non-masking' chemicals, but can go a long way towards reducing the likelihood of a trout becoming alert to the fisherman due to smell.
Also, before hitting a challenging trout stream, it never hurts to leave the cologne and other fancy deodorants back in the hotel room. On a challenging trout stream, an angler needs every edge they can get, and avoiding strange smells to finicky trout is a good way to do this.
Remember, trout have very powerful senses of smell. It is only logical that they will use this sense to identify flies presented their way to determine whether or not is something that is good to eat. A funny smelling fly, due to either chemical floatants or inadvertently smelling like Old Spice, is a good way to send a trout away from your fly and onto more 'naturally' smelling food.
Sight is of crucial important to trout, which is not surprising. After all, it's the sense that they use when determining whether or not to eat something that comes their way. Trout, in particular, have excellent close-range vision although they lack in long-range vision. This close range vision by the trout is why so many imitation flies may fail to grab the interest of a trout – the trout can easily determine if given time if the fly looks like something it is accustomed too.
A trout sees the world through what is known as the 'trout's window'. This window is a cone shaped view that extends up from the eye at an ever-increasing diameter. Thus, the deeper the trout is, the more the trout can see.
A trout will only eat something that passes within this cone of vision since this is where they can see it and inspect it. Due to their other excellent senses, trout may very well be aware of something on the water that is outside of this cone of vision. But a trout consider eating it if it sees the fly in their cone of vision.
This knowledge leads to one strategy all anglers should use when fishing to rising trout. When fly fishing to a rising trout, it is very important to drop the fly not where the rise was but upstream of where the rise was. By presenting a fly upstream from the rise, the fly will float down the river naturally, not just suddenly appearing in the trout's cone of vision, which is likely to seem suspicious to a cunning trout.
Trout also have the ability to determine color, including subtle shades of color. This is why the same fly in two different colors can produce remarkably different results when fishing, the trout may simply be eating one color insect and avoiding others.
Lastly, trout also have the ability to see the profile of a fly. Of all the characteristics of a fly, this is perhaps the most important. A fly that does not have the same profile as seen from underwater compared to what they are accustomed to eating, is not likely to be very successful. For this reason, it is always important to make sure that your flies float properly, especially when dry fly fishing.
Moreover, even if your dry fly is a spitting imitation of the real thing, it is not likely to draw strikes if your fly floats awkwardly (or partially sinks).
This is a good reason to avoid the real cheap flies you may see - the colors of these cheap flies may look right, but the profile is likely to be wrong when on the water.
Trout have an acute sense of hearing that is well worth understanding. Trout have two sound receptors. The first one runs along the length of the fish's body. This receptor picks up frequency vibrations – such as the banging of rocks or oars against a boat. A second receptor, located inside the trout's ear, is used to detect the movement of aquatic insects which the trout eats. This receptor is extremely acute, allowing the trout to hear sound frequencies well outside the human hearing range. This hearing receptor of the trout is what allows the fish to find food even in very murky water.
Because trout have such acute senses of hearing, anglers need to keep several things in mind when fishing for trout.
First, trout can't hear human voices outside of the water. Thus, having a loud conversation about something along the bank of a river will not spook the trout.
Second, trout are acutely aware of vibrations and sound that occur in the river. Banging oars on the side of a boat is a wonderful way to alert the trout to your presence, thus spooking them. Likewise, great care should be taken when wading. Wading loudly, either caused or by the splashing of the water or the movement of rocks beneath the angler's feet, is easily heard by a trout – especially in slower moving water. In fast water, these vibrations tend to get drowned out by the current and rapids. But in slower water, such as runs or spring creeks, it is crucial that an angler take care when wading.
Third, trout are easily able to hear things that fall into a river, especially in slower water. A nearby trout can readily hear a grasshopper or other bug that falls into the river. Because of this, care must be taken in casting to prevent the fly line from making a splash in the water or from having the fly itself strike the river at full force. A gently dropping fly is far more likely to attract the attention of a trout than one that gets slammed into the river due to a bad cast or too heavy of a fly or fly line.