Do hydro-biological factors influence spawning migration: A case study of Hilsa’s (Tenualosa ilisha) breeding habitat in Ganga River, India

Hilsa (Tenualosa ilisha) is an amphihaline migratory fish and established itself as one of the most important commercial fishes of the Indo-Pacific region. It has a wide range of distribution and occurs in marine, estuarine and riverine environments. T. ilisha exhibits spawning migration to the freshwater environment of the river systems and thereafter nourish young ones until they return back to sea for maturity. The breeding success of this species depends on the synchronous effects of eco-environmental and biological conditions. The fish normally inhabits the lower regions of the estuaries and the foreshore areas of the sea. Hilsa prefers to reside in the lower basin region of Ganga River during their upstream migration. Several attempts have been made to explore the feeding habit of hilsa in the River system but these are inadequate. Knowledge on the feeding habitat of hilsa and seasonal variation of biotic and abiotic components are very much essential to understand the precise breeding habitat selection of hilsa in monsoon. In the present study, it was found that high turbidity, silica loads, and specific biotic components i.e. diatom population helps upcoming hilsa to spot their preferable breeding ground in the lower basin stretch of Ganga River. Management and conservation of breeding habitat improve the productivity of the fish which is directly benefiting the socio-economy of this fishery.