During the final strike-or-don't strike impulse, smell plays a part.

Fish's nostrils work almost a million times better than a dog's. It is not uncommon for them to detect a single drop of a chemical in an area the size of an Olympic swimming pool. Their receptor system is so sophisticated that they easily home in on the source of order. Every human has an amino acid in there skin known as L-serine. It's more pronounced in some people then others. Virtually all research shows this has a negative effect on fish. In one set of experiments, a human hand was placed in the water upstream of migrating salmon. The fish immediately changed course and went up the other side of a fish ladder. When the hand was placed on the second side of the Y ladder, the fish changed their course again and proceeded up the first side. Fisherman who know this often do something to mask the human scent. The majority of game fish rely on site during the final stages of attack, but their olfactory senses often provide long-range and middle range stimuli. From an angling standpoint, the key lies in eliminating the negative smells tracks while maximizing the positive ones.

It's an element of fishing that seldom receives much attention, but it could be a major reason for not catching fish. Because our own noses are relatively ineffective, we tend to discount the importance of a fish's olfactory sense.