Demersali

Demersali (demersal species) are aquatic organisms that live and feed near the seabed. In marine biology, the term demersal describes animals that inhabit the bottom region of seas or lakes, as opposed to pelagic species that roam the open water column. Demersali primarily occur on continental shelves and slopes, on substrates such as sand, mud, rubble, or rocky bottoms, and can occupy a broad range of depths from shallow coastal zones to deep-water habitats.

Biology and ecology vary among demersal groups. Many demersal fishes are associated with the substrate and may exhibit benthic or semi-benthic habits, sometimes undertaking short vertical migrations to feed or reproduce. Diets typically include invertebrates such as crustaceans, mollusks, and polychaetes, though some species prey on smaller fish. Reproductive strategies are diverse, with some species laying demersal eggs attached to the substrate and others releasing pelagic eggs that drift in the water column.

Fisheries and management are central to discussions of demersali. Demersal fishes support substantial global fisheries, particularly on continental shelves. Fishing methods include bottom trawling, longlining, and gillnetting, which can impact seabed habitats and bycatch rates. Sustainable management often emphasizes stock assessments, gear improvements, and measures to reduce habitat disturbance and non-target catches.

Examples of demersal fishes include cod (Gadus morhua), haddock (Melanogrammus aeglefinus), hake (Merluccius spp.), and flatfishes such as sole, plaice, and turbot, as well as halibut and various groupers. The term highlights habitat over taxonomy, describing species that inhabit or rely on the seabed.