Types of Fish

There are over 30,000 documented species of fish. These species are categorized by both their anatomies and by the type of waters in which they live. Fish categorized anatomically fall in three categories: jawless fish, bony fish and cartilaginous fish. Fish categorized by water also fall in three categories: freshwater, marine (salt water) and tropical.

Categorized Anatomically

Jawless fish are fish with mouths that operate like suction cups. Their teeth are used as vices to hold prey rather than to chew. Chewing would require jaws. Jawless fish do not have scales and can be found in both fresh water and marine water. Today, there are only two kinds of jawless fish, hagfish and lampreys.

Bony fish as their name suggests, are fish whose skeletons are made of bone. The majority of fish in the world are bony fish. Bony fish can be found in all types of water.

Their teeth are used as vices to hold prey rather than to chew. Chewing would require jaws. Jawless fish do not have scales and can be found in both fresh water and marine water.

Cartilaginous fish have a skeletal structure that is made of cartilage rather than bone. Sharks, skates, chimaeras and stingrays are cartilaginous fish. Scientifically this group is known as Chondrichthyes. Cartilaginous fish live in both fresh water and marine water but the vast majority can be found in salt water.

Categorized by Water

It is important to note that fish are categorized based on what type of water they spend the majority of their lives in. Some fish can survive in both fresh and salt water.

Fresh water fish spend the majority of their lives in fresh water streams, lakes, rivers and ponds.

Marine water fish are best suited for the salinity of the ocean.

Tropical fish need the warm water of the tropics to survive.