Fish diversity and conservation status across habitat guilds in the river Rupnarayan, West Bengal, India
DOI:
https://doi.org/10.11609/jott.10279.18.8.29447-29458Keywords:
Aquatic biodiversity, biodiversity assessment, community structure, estuarine fish, freshwater conservation, fish assemblages, inland fisheries, ichthyofauna, threatened species, tidal river ecologyAbstract
The Rupnarayan River, a major tributary of the Hugli in West Bengal, extends approximately 75 km and exhibits distinct hydrological and morphological characteristics, including tidal influence, dynamic salinity gradients, and a meandering channel. The river transitions from a freshwater system upstream to a brackish estuarine environment downstream, supporting diverse floodplain habitats, fisheries, nutrient cycling, and sediment transport. A comprehensive assessment of ichthyofaunal diversity recorded 55 fish species belonging to 31 families, based on field surveys, fishers’ interviews, and secondary literature. Cyprinidae and Bagridae were the most species-rich families. The highest Shannon diversity index (H′ = 3.28) was recorded at the Denan canal confluence, indicating spatial variation in fish community composition. The assemblage included freshwater, brackish, and euryhaline species, reflecting the river’s transitional salinity regime and ecological connectivity. The river also provides important habitat for migratory fishes, including the anadromous Hilsa Shad Tenualosa ilisha and Toli Shad Tenualosa toli, and the catadromous Indian Mottled Eel Anguilla bengalensis. Several native species, such as catfishes and snakeheads, contribute to ecosystem regulation by preying on insect larvae, including mosquitoes, thereby offering natural pest control services. Fish species showed varied spatial distributions, with some restricted to specific microhabitats and others widely distributed throughout the river. Assessment against IUCN Red List categories indicated that while most recorded species were classified as Least Concern (LC), several were categorised as Near Threatened (NT), Vulnerable (VU), Data Deficient (DD), or Not Evaluated (NE). The co-occurrence of native, migratory, and exotic species highlights the complex conservation challenges associated with environmental change, fishing pressure, and species introductions. These findings provide an important baseline for developing evidence-based conservation and management strategies to maintain fish diversity, ecological integrity, and the livelihoods of communities dependent on the Rupnarayan River.
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