Senses
An angler arriving at the stream may spot the telltale rise of the fish feeding at the surface and cast with expectation. Why then do some fish refuse to take the fly, plug, or bait? What survival skill warned it? Another angler may see fish moving freely in the water but as soon as he moves quickly, the fish are startled and disappear. Why?
A brook trout is able to feel, hear, see, and taste. The lateral line on a trout has some similarities with the sonar system of a submarine. The fish can detect sound vibrations from a good distance. The trout is able to monitor the sound and identify its intensity and source through 16 to 32 feet of water. Also, sound travels five times faster underwater. The sound of a foot crunching gravel, the movements of a wading angler, an oar hitting the side of a boat, or a can hitting the deck can be detected as unnatural. It is easier to catch fish in rapids or on windy days because the water sounds dampen the noise made by the angler.
Some noises can actually attract fish. The ears of a trout are sensitive enough to hear a struggling baitfish or a swimming nymph a few feet away. A trout hunting a baitfish may first sense its vibration, then smell it before it senses it visually. Fish detect odors and may be turned off by strong unnatural smells coming off artificial lures and flies. Some anglers go so far as to soak streamers and lures in sardine oil to overcome human smell. Fish even mouth potential food and spit it out if it is not to their liking. In fact, a trout has taste buds on its jaw, snout, mouth, and throat. It only needs to touch the food with its snout to decide whether or not to ingest it.
A combination of taste and tactile sense tells the fish whether or not to eat a particular food-like substance. The item may look like food and taste like it, but the feel of the item in the fish's mouth is not right. For example, anglers who have tried to use the hard-bodied plastic nymphs report little success. Probably the plastic does not feel right and the trout rejects it. Manufacturers, aware of this problem, have devised new plastic baits whose texture is more appealing to fish.
Brook trouts' visual acuity is also very good. Though they are able to feel the vibration of a swimming nymph and taste its path as it passes, the trout uses its eyes to close in for the kill. Trout use their limited binocular ability in their rise to take flies from the surface or in the final few inches of taking a minnow. Within this short range, they are very accurate.
Although it has a blind zone directly behind and below its tail and overlapping vision above and ahead of it, the trout is able to perceive an angler before the angler spots it. The light rays which bend 48 degrees upon entering the water also bend on the way out, enabling the fish to see widely beyond its cone of vision. Fish do see well in the dark, particularly silhouettes, and they are able to distinguish size. (Figure 8-1.)
The cone of vision is that window through which the fish is able to see out into our world. A fish lying one and a half feet below the surface can see into the atmosphere through the open cone. If the fish rises to the surface, the cone becomes smaller; if it sinks, the cone becomes larger. Beyond the cone, the under-surface of the water acts like a mirror reflecting items from below. Thus an angler who stands tall in water or onshore may be observed by the fish. To overcome this, the angler should keep low by crouching if onshore or by hunching over if wading. Trout lack eyelids to protect them From too much light. In bright sunlight, brook trout are driven to seek a shaded hiding place under a rock or tree along the shore, or in the depths of a pool. The angler fishing during the day must put his bait or fly alongside one of these areas. At dawn or dusk, the long shadows provide the shade needed. The fish then move out to midstream to take advantage of the food drift. These are favored fishing times for most anglers.
It would be difficult to predict which of the senses first alerts trout to bait or to an angler. On a bright clear day, line splash, light-colored clothing, and too much casting can all disturb the fish. Wearing felt-soled waders, darker clothing, and keeping the fly or lure in the water longer to reduce casting may help you maintain consistent success.
