One of the most usual and emergent tropical anadromous species is Hilsa (Tenualosa ilisha) in West Bengal and Bangladesh. It is very popular as well as commercial fishes in Bengali cuisine. Estuary plays a significant role to make breeding and nursery grounds for different biotic and abiotic organisms. The estuary system is very much productive when it pockets an extensive load of silt and nutrients along with massive freshwater from Ganga. A significant amount of nutrients pass into the channel inlet and its tributaries that control the whole system eminently productive during the tidal fluctuations of the estuary. The present study deals with the physical, chemical, and biological diversity of water quality in the estuary and marine water. A comparative assessment has been carried out to measure the acceptable range of physicochemical parameters of water for the potential zone of hilsa fishes of the northwestern part of the Bay of Bengal. Simultaneously, fish catch data is used to validate the potentiality of hilsa fishes of the study area. Several statistical operations have been assimilated to assume the data variability and data accuracy of water quality for the suitable environment of hilsa species and to achieve the seasonal disparity of hilsa catch in the northwestern part of Bay of Bengal.