Demersal fish can be divided into two main types: strictly benthic fish which can rest on the sea floor, and benthopelagic fish which can float in the water column just above the sea floor.

The difference between pelagic and demersal fish is pelagic fish live and feed in the open water column nearer to the surface (pelagic zone) away from the seabed, whereas demersal fish live and feed on the bottom (demersal zone).

Demersal fishes are one of the major components in the marine fish landings along the Indian coast. The demersal fisheries have exploited 21 major fish groups of different biological characteristics occupying a variety of ecological niche.

Demersal fish, often colloquially termed as ‘groundfish’, inhabit the depths of seas or lakes, predominantly dwelling and foraging near or on the seabed within what is known as the demersal zone.

While pelagic fish prefer the open waters, demersal fish are the true bottom-dwellers. They reside close to the ocean floor, making homes among reefs, rocks, and sandy or muddy surfaces. Common examples of demersal fish include flounder, cod, and halibut.

Demersal fish are fish that live and feed on or near the bottom of water bodies, in contrast with pelagic fish, which live in the pelagic zone of oceans and lakes. Examples of demersal fish species include cod, haddock, and flatfish such as turbot and halibut.

Two types of fish inhabit the demersal zone: those that are heavier than water and rest on the seabed, and those that have neutral buoyancy and remain just above the substrate. In many species of fish, neutral buoyancy is maintained by a gas-filled swim bladder which can be expanded or contracted as the circumstances require.