Documentation of Vulnerable Bull Shark (Carcharhinus leucas) Occurrence in the Hooghly River, East Coast of India

The bull shark (Carcharhinus leucas) is a species of requiem shark distributed worldwide, which inhabits estuaries, nearshore areas, and the continental shelf waters and opportunistically in rivers within tropical and sub-tropical regions. In the present study, we report the first occurrence of bull shark from inland waters of the Hooghly River in the Ganga River Basin based on molecular and orphometric investigations. The identification of the specimen was confirmed through distinct morphological features, including a blunt snout, large dorsal fin, crescent-shaped mouth with sharp triangular teeth, and a muscular asymmetrical upturned tail. The percent identity of the specimen was 100% based on both the 16s rRNA and ND4 sequences. Phylogenetic analysis revealed that Carcharhinus leucas and Glyphis glyphis are closely related, forming a well-supported sister clade, while Carcharhinus falciformis was identified as a more distantly related sister taxon. This report documents the occurrence of the bull shark in the Ganga River system at the farthest inland distribution limit of the species in India. Our findings extend the known range of the bull shark within India’s inland waters and contribute valuable baseline data on biodiversity, highlighting the ecological significance of this vulnerable species within the Ganga River system.