LATERAL LINE SYSTEM (defined)
The lateral line system found in many fishes (Green Heads) and in some aquatic amphibians is sensitive to differences in water pressure. These differences may be as a consequence of changes in depth or to the current like waves caused by approaching objects. The basic sensory unit of the lateral line system is the neuromast, which is a bundle of sensory and supporting cells whose projecting hairs are encased in a gelatinous cap. The Neuromast continuously send out trains of nerve impulses. When pressure waves cause the gelatinous caps of the neuromast to move, bending the enclosed hairs, the frequency of the nerve impulses is either increased or decreased, depending on the direction of bending.
Neuromast may occur singly, in small groups called pit organs, or in rows within grooves or canals, when they are referred to as the lateral line system. The lateral line system runs along the sides of the body onto the head, where it divides into three branches, two to the snout and one to the lower jaw.
A swimming fish sets up a pressure wave in the water which is detectable by the lateral line systems of other fishes. It also sets up a bow wave in front of itself, the pressure of which is higher than that of the wave flow along its sides. These near-field differences are registered by its own lateral line system. As the fish approaches an object, such as a rock or the glass wall of an aquarium, the pressure waves around its body are distorted, and these changes are quickly detected by the lateral line system, enabling the fish to swerve or to take other suitable actions. Because vibrations in the water caused by sounding voices are waves of pressure, the lateral line system is also able to detect very low-frequency sounds of 100 Hz or less.
HEARING AND SOUND
The sound of your lure hitting and then moving through the water is actually the first thing likely to alert a fish. The movements of vibrations in the air caused by sounding voices through the water are integral to a fish's sense of hearing and to its complete survival. Fish count on two different organs working together to locate and sense sounds.
On both sides of most fish is a line of pores called the lateral Line? The pores are the opening of tiny tubes that go through the scales into the body and end near a large nerve which travels to the brain. At the end of each tube are tiny hairs that vibrate when vibrations in the air caused by sounding voices pass over them. The moving hairs stimulate the lateral line nerve. Because tubes point in different directions, fish can accurately locate the area from which a vibration emanates.
Fish also have an inner ear, similar to humans. The inner ear aids in balance and hearing. The part of the inner ear involved in sound interpretation is called the otolith, or ear bone. Hair movement in the fluid-filled sack surrounding the otolith is what stimulates the attached nerves. Vibrations in the air caused by sounding voices move through a fish's body, almost as if it was not there, and reach the otoliths making them move. When a bait fish or a lure or fly imitating food moves through the water, it gives off vibrations, which a fish can detect yards away. These vibrations can be heard and felt. When a lure is far a way, the fish feels the vibrations with its lateral lines and pinpoints the area. As the fish gets closer to your lure, the sound of its rattling bait is also picked up by the earphone. The fish then starts to rely on other senses like smell, sight and taste to figure out if your lure is really food.
Once the gap between fish and lure narrows even more, the sense of sight plays a bigger role. Fish eyes work much the same way human eyes do, similar to a camera. There are some differences through. Fish doesn't have eyelids or tear ducts, and they don't have an iris that changes to different amounts of light.
Fish eyes are sensitive to movement. They have plenty of special cells called rods that alert them to movement and contrast and each eye can detect these on their own. Because fish has eyes on the sides of their heads, they can see nearly all around themselves. However, like our own eyes, the two eyes must work together to enable the fish to see in three dimensions, allowing the fish to figure out distance from an object. Furthermore, because the eyes are on opposite sides of their head, fish only have a narrow area of this "binocular vision" - directly in front and above their snouts.
This makes fish relatively nearsighted - while they can make out movement and images at a distance, they can't see them clearly or judge the distance or depth. That's why Bass often swim right adjoining your bait or lure, close enough to eat it before turning away.
Scientists believe that freshwater fish can see color. Most researchers strongly believe that fish have three sets of cells called cones in the eye that allow for color perception. They strongly believe that two sets of cones are sensitive to color while the third picks up ultraviolet light, which we can't detect with our naked eyes.