A good trout bait must appeal both to a trout's sense of smell and taste. A fish can sense food by either smelling or tasting the water. The sense of smell in fishes is relatively acute, as has been proved by numerous experiments. Trout are no exception. There is a pair of nostrils on either side of the snout of a trout, but these are not used for breathing.
Water enters one nostril, then passes over several folds of skin and out the other.
It is well known that salmon are keenly aware of various odors, including the odors of a man's hand placed in the water. It is likely that trout have as keen or nearly as keen a sense of smell as do salmon. A fish has nerve endings scattered over most of its body surface and responds to touch stimuli, but its response is often unlike that of man and many other higher animals. That is why a fish can be stuck by a hook and return in a moment to strike at the hook again. Without doubt it has felt the hook, but whether or not it has felt pain is difficult to say, since we judge such matters only by our own standards.