A 54kg fish locally known as tabal was caught in the Bay of Bengal near Kuakata in Patuakhali and brought to Mahipur fishing port.
Fishers aboard the FB Salma Karim caught the specimen, which was sold in an open auction for Tk36,000.
Local fish trader Rubel Gharami bought the fish and said it weighed 54kg.
Upazila Senior Fisheries Officer Apu Saha said the fish belongs to the marine Carangidae family and has economic value.
Fishers said the species occurs in the deep sea, but fish of this size are not commonly caught.
The fish is also called tabli, boga or khadia in the Kuakata area.
Research assistant Md Bakhtiar Rahman said the capture of a large specimen could be a positive indicator for marine biodiversity in the Bay of Bengal.
Gharami kept the fish on ice for planned sale in Dhaka.