Predation and Perception
Fish do not have large brains that have them analyse a lure, leader and other mechanics of a presented lure. They respond to conditions by reacting and their responses are rather limited.
While it does not take a lot of smarts to outwit a fish, it does require a good understanding of their senses, which are very sensitive. Some sense are stronger in some species than others depending on the species and their habitat. Those fish that have a keen sense of movement or vibration are better caught with live bait, but can be scared away with lines or leaders that suffer from vibration. Those with excellent eye sight can be scared away from line colour or a wire leader, while others are attracted by specific bright colours and others by dull colours.
One of their most popular responses is to food and their urge to feed is very strong regardless of the species. They also have a strong sense of survival with reproduction their next biggest urge, which often takes over all other needs. Understand how they respond in each situation will help you understand what technique to use.
Fish strike for various reasons and it is not always for food. Sometimes they respond out of hunger, other they respond to defend.
The key is understanding the fish you want to catch and appealing to its senses and avoid those movements, lures, baits and tackle that wills care them away.
All fish have the ability to smell and each species is different than the other. While we do not know to what degree they can smell, we do know that human odours do repel fish and that baits like worms that have smells most likely do a better job of masking human odours than attracting the fish. In this case, there is a greater chance to push fish away with odour than to attract.
Fish have a great sense of hearing, yet their sense of sight is much more limited in the best of fish in terms of how we can see. Water, even when clear, is difficult so see through in vast distances. Many would argue, and be correct, in that fish can see much better through sound than they can through their eyes.
However, in clear water, fish do respond to certain colours more than others. You can also appeal to their sense of hungry with life like replicas of their most popular foods. Just because a colour range works well on one species, which is no guarantee that it will work well for all species: fFor example, Pacific Salmon and more colour-centric than their related cousins the trout. Once again, knowing these details will improve your success with the right techniques.
Fish hear well. Not only do they hear better than we do, but they have the ability to hear sounds outside of our audible range. Understanding this is critical because sounds in water travel much further than in air so be careful not to scare them by walking loudly on a dock, dropping things in a boat or anything else that will cause a vibration.
However, mimicking the sounds made by injured fish and other prey will increase your chances of success.
As with sight, there is no real consensus regarding a fish's ability to taste. However, it is important to understand that some fish taste by bumping into the lure with external sensory organs, which appear like whiskers: catfish have the most recognisable barbs. Those fish without barbs often mouth a lure to see if it is worth eating. Those fish that mouth a lure will quickly spit it out if they detect it is not food. For these fish, a quick yank of the line is needed when using a lure, though live bait would work best. Again, understand your prey's preference.