Indian shad or hilsa, a favoured fish which migrates into the rivers of the Bay of Bengal. These, like salmon, are anadromous - born in rivers, live life in the oceans, and then come back to the same river to spawn and die. Siddharth Dasgupta makes the point that they are known and sold by the river where they are caught - Ganga ilish, Padma ilish, etcc. The taste from river to river can be very different because their level of fish oil and other natural flavour molecules depends on their journey upstream when going to spawn - just as Copper River Salmon, or Severn salmon tastes different from other salmon.
