Here is some information about how fish live and breathe, so to speak.
How do fish …
Swim? Fish swim by flexing their body and tail (caudal fin) back and forth. They do this by expanding the muscles on one side of the body while relaxing the muscles on the other, which propels them forward through the water.
Breathe? Fish breathe by opening and closing their gill covers to pump water past the gills. They need a constant supply of oxygen, which they get from the water.
See? Fish see best at close range with eyes that are similar to those of humans.
Smell? Fish smell through two openings on their head. The sense of smell helps fish find food and warns of danger.
Taste? Fish use taste buds, just like humans do. Some are on their tongue and others are on the outside of their body. The taste buds are able to distinguish between sweet, salty, sour, and bitter.
Hear? Fish “hear” by picking up pressure changes and vibrations in the water through a lateral line (a system of thousands of tiny hair cells that run the length of a fish's body and work as a sensory organ) along each side of their body. The lateral line helps a fish to find and capture food and avoid enemies. Fish also can detect vibrations in the water through internal ear bones called otoliths; the brain interprets these vibrations as sound.
Reproduce? Fish reproduce differently according to species but generally follow one of three methods. In most cases, a female drops eggs into the water, where they are immediately fertilized by sperm from a male. In the second method, the eggs are fertilized within the female's body before she drops them into the water. In the third method, the female retains the eggs within her body, and the young are born alive. (Some sharks and guppies give birth this way.)
Learn anything new here? Now you've been to fish school!
To capture the fish is not all of the fishing.
–Zane Grey, American author (1872–1939)