Fish Facts

  • Fishes are cold-blooded and they can't control their body temperature.
  • Fish can feel pain. They have a good sense of taste, sight and touch. Many fish taste without opening their mouth.
  • Whale shark is the largest fish and they can grow to 50 feet long.
  • Fish like Trigger fish can swim backwards.
  • If gold fish is kept in a dark room it will lose its color.

Characteristic of fish

Fish are aquatic vertebrates that have vertebral column called spine. A classic fish is a torpedo shaped. The fish contains head containing a brain and sensory organs, a trunk with a muscular wall surrounding a cavity with the internal organs and a muscular post-anal tail. The following are the general characteristic that all the fish species posses:

General characteristic:

  • Ectothermic
  • Lateral line
  • Two chambered heart
  • Gills used for respiration
  • No external ears
  • No eye lids

All the species of the fish found in the world are classified into the following three groups. They are:

  • Agnatha - jawless fish
  • Chrondrichthyes - cartilaginous fish
  • Osteichthyes - bony fish
    • Ray finned group
    • Lobe finned group

Each type of fish has its own characteristic based on the group they belong. So it is easy to study the characteristic of a fish based on their group.

Agnatha class:

  • Jaws are absent
  • Fins are absent
  • Skeleton is made up of cartilage
  • Posses round eel like body
  • Absence of swim bladder and gill covers
  • Soft skins made up of scales
  • Oviparous animals
  • Found in marine and fresh water

Chondrichthyes class:

  • Cartilage make up the skeleton
  • Body is covered with triangular placoid scales
  • Posses ventral subterminal mouth
  • Fins are stiff and non-flexible
  • Absence of swim bladder
  • Internal fertilization
  • Found only in marine water

Osteichthyes class:

  • Bones make up the skeleton
  • The gills are covered with operculum
  • Swim bladder is present
  • Fins are made up of rays and spines
  • This species posses different types of scales
  • External fertilization

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