Biology of Fishes

Worldwide, there are over 22,000 species of fish, comprising more than 50% of all vertebrate species. The origin of fishes dates back to over 480 million years. Fish evolved in fresh water; the chondrichthyes moved to the sea early in evolution, while the bony fishes went through most of their evolution in fresh water and spread to the seas at a much later period. Fish are the dominant free swimming animals of the seas. The structure of a fish body is designed for ease of movement. This ability to move about easily, without relying on water currents to carry them about, has enabled fishes to exploit most parts of the world’s oceans, and this is reflected in an extraordinary variety of sizes and shapes. Fish are found in both fresh and salt water worldwide, and are a very important food source for many nations. Fish come in all shapes and sizes, some are free swimming, while others rest on the bottom of the sea, some are herbivores and others are carnivores, and some lay eggs while others give live birth and parental care to their young. This is an ideal textbook for students of fish biology and any of the branches of aquatic biology.