Fish

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 are generally scaled and breathe by passing water over gills. Modern fish are divided into three classes:

1. AGNATHA . Primitive, they lack a jaw and a bony skeleton meaning they are very flexible.Lampreys and Hagfish are the only living representatives of this once large class.

2. CHONDRICHTHYES. The jawed fish with cartilaginous skeletons. These were the first fish to exhibit paired fins. Their skin is covered with teethlike denticles which gives it the texture and abrasive quality of sandpaper. Tpyes of fish include Sharks, Rays, Rat-Fishes

III. OSTEICHTHYES. Fish with bony skeletons. With over 20,000 species worldwide. Lungfish, Trout, Bass, Salmon, Perch, Parrot Fish. The bony fish have evolved to be of almost every imaginable shape and size, and exploit most marine and freshwater habitats on earth.

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.