Demersal Fish
Demersal fish live on or near the seafloor, feeding on benthic invertebrates like worms and crustaceans. They stay close to the bottom, unlike open-water pelagic species.
Demersal fish are a group of aquatic organisms that live and feed on or near the seafloor, relying on the benthic zone for food and shelter. Unlike pelagic fish that inhabit open water, demersal species stay close to the bottom substrate, often interacting directly with sediment and invertebrates. This term encompasses various species adapted to near-bottom environments, including many commercially important groundfish.
What this means in real life
A flounder lies flat on the sandy ocean bottom, using its flattened body to hide from predators and ambush small prey passing overhead—this bottom-dwelling lifestyle makes it demersal, unlike a tuna that swims freely through open ocean.
What it isn’t
Demersal does not mean 'bottom-feeding' in the sense of eating garbage or waste. Many demersal fish are selective hunters or scavengers of legitimate seafloor organisms; the term simply describes where they live, not the quality of their diet.
Commonly misused online
Social media often conflates 'demersal' with 'bottom-feeder' as a pejorative, implying the fish are dirty or inferior. In reality, demersal is a neutral ecological classification; many demersal species are commercially valuable and nutritious.