Demersal Fish a slow moving and dorso-ventrally flattened fish. The mouth is fully or slightly vented towards ventral side. The dorsal side of body is relatively dark; they are either carnivores or detritus feeders. The young spends early life at the pelagic level. Marine fish production largely depends on presence of demersal fishes. However, though they are bottom dwelling fish, only a few species live at great depths of the sea floor, and these fishes have almost no commercial importance.
Marine fishing dealing with demersal fish, is generally confined to shallow ocean/sea floor where dredging/trawling is possible by trawl nets. In the bay of bengal, demersal fishes occupy a significant place in total marine landing. In fact, stock assessment of marine fish in the Bay of Bengal is based on demersal fishes. Main fishes of this category include Sea Catfish, Jewfish, Silvery Croaker, Seabream, Perch, ribbon fish, Snapper, Eel, Grouper, Silver Bream, Indian Barracuda, Black Bass, Rabbit Fish, Crab Eater, Bastard Halibut, Long Snout Scavenger, Blackbrow Snapper, Red-breasted Goatfish, Striped Grunter, Banded Sweet Fish, Flounder, Plaice, Sole, Asian Psettodid, Rock Fish, and Demersal Shark. In addition, several species of shrimps are also found at the bottom layer. Several species of sharks also live near the bottom and can be grouped as demersal fishes. Sometimes demersal fishes are harvested as non-target species. In Bangladesh most demersal fishes are generally harvested by bottom gill nets, three layered trammel nets, fixed bottom set bagnets, long lining, etc.
Among demersal stocks, shrimps (though not a fish) are most valued species; a significant amount of exportable shrimp from Bangladesh actually comes from the demersal stock of the Bay of Bengal. Unlike most pelagic fish, demersal fishes contain relatively less fat, and thus share a prominent place in seafood dishes. Among demersal fishes of the Bay of Bengal, Jewfish and Crockers have recently got international markets; salted products of these are now exported to Hong Kong and Singapore. Most of the other demersal fishes harvested locally are either consumed or used as fishmeal. [Md Abul Hossain]