Fish have senses beyond our own that aid them in their underwater environment.
Like humans, fish experience the senses of smell, taste, sight, touch and hearing. Beyond our five, fish also can detect motion, subtle changes in current and vibrations in the water; some fish even have an aura that other fish can detect.
- Sight: Most fish that are diurnal, or active during the day, have well-developed eyes which allow them to see almost as well as we do. The majority of diurnal fish also can see in color and are able to focus on near and far objects. Nocturnal species, those active in the dark, usually do not see color well, but have large eyes and pupils which allow them to see as well as cats.
- Sound: Many fish have a keen sense of hearing and can even hear sounds made above the water if they are loud enough. Fish “ears” are enclosed in a chamber on either side of their head. They have no outer ear or eardrums to receive sound vibrations. Vibrations are carried by body tissues to the inner ear.
- Touch: A fish’s sense of touch is provided primarily by what is called the “lateral line” system. The lateral line is a network of tubes, located just beneath the scales, which extends all over the animal’s head and runs down the sides of its body. If you examine a larger or scale-less fish, the lateral line is visible as pores or holes in the fish’s skin spaced at relatively regular intervals, especially down the sides of the fish. This allows them to detect when another fish is swimming nearby. Fish also have nerve endings throughout the skin that react to the slightest pressure and change of temperature. This keen sense of touch keeps them from swimming into unfavorable waters.
- Smell and Taste: Fish have a sense of smell and taste that is far superior to our own. Some fish smell with their noses and the front of their faces. Catfish even smell with their barbels (whisker-like things). A variety of fishes have taste buds in their mouths, but also all over their heads and much of their bodies. These taste buds respond to minute quantities of chemicals in water. Certain chemicals stimulate taste buds in a positive way and entice the fish into feeding.
- Other Senses: Fish also have a sense that helps them keep their balance. The inner ear contains a fluid and hard, free-moving otoliths (ear stones). These otoliths move over nerve endings in the ear whenever the fish swims in a non-upright position. The nerves and brain communicate with the fin muscles which move to restore the fish’s balance.
Aquarium fish are varied and amazing creatures. They have very sensitive sensory organs that are adapted to the aquatic environment. Some fish can even create and detect weak electrical fields and use small modulations in these field’s “auras” to communicate with each other.