Abstract
Subarnarekha River is an important riverine ecosystem inhibits both freshwater and estuarine fishes due to its diverse habitat condition. This river basin encompasses 0.6% of India’s total geographical area and is trans state river that traverses up to 460 km passing through Jharkhand, West Bengal, and Odisha before discharging into the Bay of Bengal. Over the years, alterations in river’s ecology, fish biodiversity and ecosystem services have substantially affected due to negative impacts of anthropogenic activities majorly by climate change, pollution, mining, land use change, overfishing and damming along the river. The change in riverine environment has disturbed the inhibited aquatic life and raised matter for assessing the riverine environment in consideration to fish biodiversity and habitat status in spatiotemporal scale with causative factors impacting fish and habitat. Henceforth, an exploratory survey was conducted during 2023-24 to assess fish biodiversity and habitat attributes along the entire stretch of the river from origin to destination.
The investigation from 10 sampling points along the river revealed 75 fish species of which 53.33% were estuarine fishes and 46.67% were freshwater. The taxonomic status of fishes belonged to 16 orders, 35 families, and 58 gen era, with Perciformes (34.67%) as the most dominant order followed by Cypriniformes (21.33%). Cyprinidae family had the highest species diversity and the feeding pattern of the fishes were; carnivorous (44%), omnivorous (22.22%), herbivorous (12.5%), planktivorous (12.5%), detritivorous (6.9%), and larvivorous (1.38%). The IUCN Red List assessment of the species revealed 6.9% as Near Threatened, 2.7% as Vulnerable, and 1.38% as Endangered. The water quality assessment in Ranchi indicated increased levels of ammonia and chlorine, and reduced dissolved oxygen not suitable for fish propagation. Besides, water quality assessment in the two dams viz. Getalsud and Chandil along the river indicated low dissolved oxygen that could be due to excessive eutrophication.
The study emphasizes for improved conservation and management practices with hand holdings from government agencies and other stakeholders to improve the river health and its fish biodiversity by mitigating/ reducing the impacts of anthropogenic threats.