Fish of the Ocean
A lesson on the physical features of ocean fish. The reading is accompanied by true/false questions.
• To introduce students to the physical features of ocean fish.
Approximately 71% of the surface of the earth is covered by ocean waters which makes salt water the largest habitat on earth. There are over a million and a half species of living plants and animals on earth and about 30,000 of these species are classified as fish. Fish are subdivided by the composition of their skeleton: cartilage or bone. Sharks and rays are primary examples of fish with cartilaginous skeletons. Fish with a skeleton composed of bone are simply called bony fish and are vertebrates, members of the scientific superclass Osteichthyes. Ichthyology is the study of fish of all kinds and researchers discover about 250 new species of fish each year as they explore the vast breadth and depth of the ocean.
A particular species of bony fish is adapted to inhabit a freshwater or saltwater environment and only a few species are able to survive in both freshwater and saltwater. Most species of salmon are born in freshwater, migrate to the Atlantic or Pacific Ocean for their adult life and return to their freshwater birthplace to reproduce and die.