Morphometric and Molecular Assessment of Tor putitora and Neolissochilus hexagonolepis Population in Jia Bhoroli river Ecotone Zone, Assam

Background: Ecotones are areas of overlap between different ecosystems, referred to as ‘junction zones or tension belts’, that harbor a distinct collection of organisms. Tor putitora and Neolissochilus hexagonolepis are two threatened Mahseer species which requires urgent conservation attention. Bhalukpung area in the River Jia Bhoroli is an ideal example of an ecotone, as its ecosystem transforms from resembling a foothill river ecosystem to a river floodplain ecosystem. However, studies on threatened fish populations in ecotone zones, which could be used as conservation sites, are lacking. Therefore, the present study aims to generate firsthand information on the relationship between the populations of these threatened fish and their foothill-floodplain river interface ecotone in the Jia Bhoroli River. Methods: The data on water quality, topography was collected for a period of one year from January to December, 2021 along with fish samples. The mahseer species were identified and catch per unit effort (CPUE) was also calculated. Result: Identification of the collected mahseer fish as T. putitora and N. hexagonolepis were confirmed using both morphometric as well as molecular tools. CPUE was found to be 4.3-12.6 for N. hexagonolepis and 4.1-10.3 for T. putitora. The ecotone zone was found to have a thriving mahseer population and ecotones are believed to play a crucial role as a diverse food source for the fish. Conserving Bhalukpong as a designated ecotone site in the Jia Bhoroli River as a fish sanctuary can help to protect their populations. Further research that encompasses all aspects of ecology is recommended for the future.