The two methods currently in ruthless commercial use are mid-water trawling and purse seining.
Before the invention of mid-water trawls, drift nets, with surrounding nets, were the principal gear for fishing pelagic fishes.
They are notable mid-water predators, and in turn it is thought that they may be an important food for larger fishes, such as tunas and swordfish.
The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others.
The extinct heterostracans include obvious bottom dwellers (Drepanaspis) and others (Pteraspis) that were apparently adapted to mid-water, or nektonic, life.
Fisheries are classified in part by type of water: fresh water lake, river, and pond and salt water inshore, mid-water, and deep sea.
Two types of fish are caught: demersal, living at or near the bottom, although sometimes in mid-water; and pelagic, living in the open sea near the surface.
Another dragged net is the trawl, a large, cone-shaped bag of netting that is dragged along the seabed or towed in mid-water between the seabed and surface.
One extraordinary strategy used by the hemipteran insects Buenoa and Anisops is an internal oxygen store that enables them to lurk for minutes without resurfacing while awaiting food in relatively predator-free but oxygen-poor mid-water zones.
These methods, however, have yet to be demonstrated for mid-water pelagic or semi-pelagic fishes.
