Fish

Fish live their entire lives underwater, both in saltwater and fresh. Species of fish inhabit every waterway known to man, from mountain streams to the depths of the deepest ocean. Fish serve as a source of food for many animals, including man as well as provide entertainment in the form of fish keeping.

Fish can be recognized in several ways, but the most notable characteristics of fish include:
1. Fish utilize gills to filter air from water.
2. Fish have two pairs of fins and several unpaired fins
3. Fish are egg layers and the young are hatched with the ability to fend for themselves

A typical fish has a torpedo shaped streamlined body and are coldblooded. Most fish are covered with scales and produce a mucous layer to protect them from injury. There are exceptions, most notably several amphibious species of fish that can live and move about on land for several days before returning to the water and fish that are not purely coldblooded, like the Mako, who can actually produce heat internally allowing them to hunt more effectively.

Previously, fish were thought to be lacking the nervous system structure to feel pain or fear, though these thoughts are now being challenged. In an experiment conducted by Williams Tavolga, certain fish responded by grunting after an electric shock was administered and that over a period of time, only the sight of the apparatus alone caused the fish to react in a similar manner. The results of these experiments were followed up by another study and where fish were injected with bee venom. These fish began to show signs of discomfort and pain by rubbing themselves along the walls and bottom of the aquariums which was interpreted as an attempt to relive the pain. These studies in themselves have been inconclusive, though, and more in depth research is needed before a statement can be made.

Fun Facts About Fish
1. Fish have been the dominate form of sea life for many thousands of years
2. Fish have colored our history with legends of mermaids and our literature like The Old Man and the Sea
3. Many fish species live in large familiar groups called schools.