Fish are aquatic vertebrates that are typically cold blooded, covered with scales, and equipped with two sets of paired fins and several unpaired fins.
Fish are abundant in the sea and in freshwaters, with species being known from mountain streams (e.g., char and gudgeon) as well as in the deepest depths of the ocean (e.g., gulpers and anglerfish).
Fish account for more than half of the known vertebrates.
There are at least 24,600 known species of fish, of which over 23,000 are bony fish, with the remainder being about 850 sharks, rays, and chimeras and about 85 hagfishes and lampreys.
They range in size from the 16 m (51 ft) whale shark to a 8 mm (just over 1/4 of an inch) long stout infantfish.
They are of tremendous importance as food for people around the world, being either collected from the wild or being farmed in much the same way as cattle or chickens.