What do fish look like in the water column?

Depending on whether they live in open water or on the bottom, fish in the water column have a morphology adapted to their living environment.

A body shape to suit their lifestyle

Pelagic fish

A pelagic fish is a fish that lives between the surface and the seabed, but does not depend on the seabed for food. It lives far from the coast in the open sea. Mackerel, herring or pilchards are pelagic fish just like tuna and swordfish.

  •  Their streamlined bodies enable them to move quickly,
  • Their blue-green backs protect them from birds and marine predators,
  • They live and swim in shoals that are made up of individuals of the same size.
  • Fish larvae that are zooplankton are pelagic

Jellyfish, squid, sharks, marine mammals and sea turtles are also pelagic marine animals.

Demersal fish

A demersal fish is a fish that lives above the seabed and depends on it for food. Sea bream, cod, pout, gurnard, hake and whiting are demersal fish, as are groupers, which live on rocky bottoms.

  •    Their colour varies from grey to red,
  •    The barbels of cod or pout are used to scour the mud.

Benthic fish

A benthic fish is a fish that lives on the bottom and depends on the sediment for food. Rays and skates, sole, shrimp, lobster, mussels and scallops live on the bottom.

  • Benthic fish move along the bottom,
  • It often has a flattened shape like skate, plaice or sole.
  • It sometimes burrows to the seabed to disappear from the eyes of its predators.
  • Benthic fish such as sole have a pelagic life stage when they are larvae; they settle on the bottom as adults.

Did you know? 

During the period when herring were breeding, scientists observed a shoal of 250 million individuals stretching for about 40 km! Pelagic species account for about half of the world's catch.

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