These are called Ikan Baong. Being top feeders they are avoided by the Malays in particular. Many others do not eat them for other reasons perhaps. However these fish are tasty if you know how to cook them and in the past they have helped many poorer families as a source of good and even free protein.
further afield the Baong is a valued fish from the natural habitats of the Kalimantan rivers. The Indonesians like the fish smoked (salai) or BBQed (pangang) besides they like to cook this fish with terong asam (or the Iban Terong of Sarawak) in soup. Tumeric is often used to cook the baong in Java. Some folks like to eat curried baong. So the recipes can be really varied and it is only your imagination that can bring this fish to a great level of gourmet cooking.
As a kid I enjoyed eating this fish cooked as a soup Foochow style - the way my Third Uncle cooked it. Today many of my friends would just call it "sup terjun". Uncle Pang Sing would catch quite a number of Ikan Baong in the Rajang River and come home whistling in the happy manner he always did.
My third aunt (Nguk Ling) would start the wood fire and chop the ginger. Grandmother Lian Tie would take out the red wine. The water would come to the boil and the ingredients would be added. By then uncle would have gutted the fish and sliced them into pieces ready for the pot.
We would either have the fish as supper( siaw yeh) or part of the big evening dinner with rice depending on what time my uncle caught the fish.
Gone are the days when a happy man could throw a jala into the river and come home with a pailful of fish and/or prawns. The Rajang was teeming with fish and it was truly a Mother River - a great provider.
Today the river is dying - dying - dying. We have to do something before it is too late.