Phylum:   Chordata


  • Fish are so abundant and there is a huge variety.
  • Today there are still new species being discovered.  
  • Animals possessing a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle and a post anal tail for at least some period of their life cycles.-
  • Are bilaterally symmetric, deuterostome coelomates and the vertebrate chordates display segmentation



  • All waters on earth


  • Can be found in Oceans, Lakes and Rivers, Caves


Bodies come in differnt shapes and sizes


  • More or less torpedo-shaped with a slightly rounded head and a long, thin tapering body. Examples include wahoo, barracudas, tunas and many open-ocean sharks such as blues, makos and oceanic whitetips. Generally speaking, fusiform-shaped fishes are the fastest swimmers.

Laterally Compressed:

  • Flattened from side to side, as is the case with angelfishes, filefishes, butterflyfishes and damselfishes such as garibaldi and sergeant majors.

Dorsoventrally Compressed:

  • Flattened from top to bottom, thus creating a wide, flat profile.
  • Examples include stingrays, angel sharks, crocodile fish, and flatfishes such as halibuts, turbots and flounders.


  • Long and thin, having a body diameter that is very small compared with the length.
  • Classice example are Eels. Eels grip the water with one side of their bodies and push with the other as they “ess” their way along.
  • Eels are fishes.
  • Sea snakes are reptiles, not fish, but swim in a similar manner.


  • Each with comparatively few representatives such as sea horses, cowfishes, trunkfishes and boxfishes.



  • All animals need oxygen to fuel metabolism, Terrestrial animals breathe air, fish rely on oxygen dissolved in the water
  • Evolved Gills are complex, multi layered organs that absorb oxygen from the water and excrete carbon dioxide. Gills only work when oxygenated water is constantly streaming through them. This is why fish and sharks are always moving.


 There are three main classes of fish

1. Osteichthys or Bony Fish

-Includes both ray-finned and lobe-finned fish

-Over 30,000 Species. Some common name groups

  • Anglerfish
  • Barracudas and snooks
  • Blennies
  • Blue Devils and hulafish
  • Boarfish and allies
  • Bullseyes
  • Cardinalfish
  • Clingfish and shore-eels
  • Cods
  • Cowfish
  • cusk-eels, ling and allies
  • Damselfish
  • Dolphinfish
  • Dories
  • Duckbills
  • Eels
  • Flatfish and flounders
  • Flatheads
  • Flyingfish
  • Galaxiids
  • Garfish, halfbeaks and longtoms
  • Giant herrings
  • Goatfish
  • Gudgeons
  • Gurnard perches
  • Gurnards
  • Hairtails
  • Hardyheads
  • Icefish
  • Kelpfish
  • Knifejaws
  • Lampreys
  • Mackeral and tunas
  • Moonfish
  • Morwongs
  • Mullets
  • Mulloways
  • Ocean perches
  • Old wives
  • Pikes
  • Porcupinefish
  • Prowfish
  • Puffers and Filefishes                             Tetraodontiformes 
  • Red snapper
  • Redbaits
  • Ribbonfishes
  • Roughies
  • Salmons and allies
  • Sandburrowers
  • Sandfishes
  • Sardines, pilchards and allies
  • Scorpionfish
  • Sea Moths
  • Seabream
  • Seahorses, pipefish and allies
  • Seaperches and allies
  • Silver biddies
  • Splendid perches
  • Stargazers
  • Stinkfishes and dragonets
  • Sunfish
  • Sweep and allies
  • Tailors
  • Thornfish
  • Threadsails
  • Toadfish                                                          Batrachoidiformes
  • Trevallies and allies
  • Triplefins
  • Trouts
  • Trumpeters
  • Velvetfish
  • Weedfish and snakeblennies
  • Whitings
  • Wrasses, rock whiting and allies


2.  Chondrichtyes or cartilaginous fish:

Includes sharks, rays, skates

  • Sharks
  • Stingrays, stingarees and allies

3.  Agnatha or jawless fish:

Includes hagfish and lampreys  




WoRMS (2020). Chordata. Accessed at: on 2020-07-03

AnimalsWorld (2021). Classification of Fish. Accessed at: on 2022-01-14