The species caught tend to be relatively large and of high value compared with typical pelagic species, but there are exceptions to such generalizations.
For example the industrial (fishmeal) fisheries of the North Sea, which take over half of the total fish catch, are principally based on low-value demersal species which live in or close to the seabed (sand eels, small gadoids).
Piscivores may either be active hunters, stealthers, or ambush predators.
The latter two are often well camouflaged and obtain their prey by slowly approaching the prey or a ‘lie-and-wait’ strategy.
Demersal species frequently occur in mid-water and pelagic species occur close to the seabed, so that ‘demersal’ species are frequently caught in ‘pelagic’ fisheries and ‘pelagic’ species in demersal fisheries.
The five demersal marine fish with the highest average catches over the decade 1990–2000 are Alaska pollock, Atlantic cod, sand eels, blue whiting, and Argentine hake ().
All these species spend a considerable proportion of their time in midwater.
Models of papyrus pair trawlers were found in Egyptian graves dating back 3000 years.
The intensity of fishing activity throughout the world, including demersal fisheries, has increased rapidly over the past century, with more fishing vessels, greater engine power, better fishing gear, and improved navigational aids.