Asa fish is one of the most expensive types of fish in Nigeria. It is not farmed, but gotten from the fresh waters of Southern Nigeria, where it dwells in shallow, slow moving water. It is also called freshwater rat-tail, frank fish, or African knifefish. It is an electric fish, not so bony, with shiny skin. It is dried mangala style. Mangala fish is a fish that is cut into smaller pieces before it is wood-smoked.