2.1.2. Other marine Classifications

Other marine Classifications

Marine organisms can be classified in several other ways according to their:

  1. Oceanic distribution
  2. Water salinity tolerance
  3. Water temperature tolerance
  4. Position in water column
  5. Habitat
  6. Diet.


Oceanic distribution:

Marine organisms can be classified according to the oceans in which they are found such as in the pacific, Atlantic or in the Indian Ocean.


 Water temperature tolerance:

The marine organisms are classified according to their geographical belt in which they found.

Geographical belt indicate temperature in which the organism need to survive.

The geographical belts are tropical temperature and polar.

Tropical fish: fish that have evolved to live in warmer tropical water are known as tropical


Temperate fish: Fish that have evolved to live in cooler temperate waters are known as temperate fish.


Water Salinity Tolerance:

  • Fish can be classified to their tolerance to salt levels. The two main

                                              groups are

  1. Fresh Water
  2. Sea water (marine)

Anadromous Fishes: Some fish spend the adult phase of their life cycle in salt water but moves up streams and rivers to spawn are known as Anadromous fishes.


Catadromous Fishes: Some fish spend most of their life in fresh water but spawn in salt water. Ex: eel.


Position in water coloumn:

            Organism can be classified according to their position in the water coloumn.

            Organisms can be

  1. Benthic (Benthos) —- Live on the bottom.
  2. Pelagic —– live in the open ocean.


Benthos: It can be subdivided into 4 groups

  1. Littoral
  2. Demersal
  3. Bathy
  4. Abyssal


Littoral organisms: They live within the tide and splash Zone of the seashore.


Demersal organisms: They live on the continental shelf.


Bathy organisms: they live on the continental slope.


Abyssal organisms: they live on the abyssal plain beyond the continental slope.


Pelagic organisms: they live in the open ocean closer to the surface.

                                    It may be subdivided into two groups.

  1. Planktonic
  2. Nektonic.


                   Planktonic organisms: planktonic organisms float, or swim, so feebly that their position is governed by sea currents. They are mostly                 microscopic plants and animals.

                   Nektonic Organisms:

                                        They are swimming animals

                                        They swim actively

                                        All animals other than plankton are included in nektonic organisms.

                                                      Ex:         1. Fishes, birds, mammals.

                                                                    2. Migratory fish such as tuna, shark, bill fish.



Habitat refers to the place where the organisms live.

Fish have adapted to live in a range of different habitats including

  1. Rivers. (eg: Salmon, Catla, Rohu etc)
  2. Mangroves. (Oysters, mudcrabs, shrimps etc)
  3. Lagoons. (Prawns, Mullets, seaurchins etc)
  4. Reefs. (Giant clam, Lobster, Parrot fish etc)
  5. Oceans. (Tuna, Shark, Trevally etc)

DIET: Based on the food consumption fishes are classified mainly into three types.

                        Herbivores: The fishes which eat plant or plant materials are called as Herbivorous fish. (ex. Surgeon fish, Grass carp etc)

                        Carnivores: The fishes which eat other animals are called as carnivorous fish. (ex. Tuna, Shark etc)

                        Omnivores: The fish which eat both animal and plant materials are called as omnivorous. (eg. Silver sprat, fusiliers etc)


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