Fish diversity of the Beki River, Assam, India: Present status and conservation needs

The state of Assam in India is recognized as one of the hotspots of freshwater fish diversity. Beki River is an important tributary of the Brahmaputra River. A significant decrease in freshwater fish in this region has been a major source of concern in recent years. The fish diversity of this region has encountered various anthropogenic threats that have led to the loss of biodiversity. In this study, fish diversity was studied in six fish landing zone of Beki River and 31 species of fish were recorded. The ichthyofaunal diversity of the Beki River belongs to the following families - Bagridae (9.67 %), Balitoridae (3.22 %), Belonidae (3.22 %), Claridae (3.22 %), Cyprinidae (64.51 %), Mastacembelidae (3.22 %), Osphronemidae (3.22 %), Schilbeidae (6.45 %) Siluridae (3.22 %). The study recorded Cypriniformes as the most dominant group and Cyprinidae as the most species-rich family.The rich diversity of fish like Ailia coila, Tor putitora, Cirrhinus mrigala, Puntius conchonius, Puntius gelius, and Puntius terio was recorded in the Beki River. Exotic species like Clarias gariepinnus, which was reported in the present study, are of major concern as they may be a threat to the indigenous species in near future. Species like Puntius phutunio, Systomus sarana, and Clupisoma garua are now facing population depletion. Shannon index of 3.33 at L5 (Uttarganakguri), 3.21 at L4 (Nizdamaka), and 3.11 at L1 (Gobardhana) indicate good diversity while 2.98 at L2 (Safakama), 2.97 at L3 (Dumnighat) and 2.88 at L6 (Madulijar) sampling sites indicates moderately polluted water. There are some serious threats in Beki River regarding fish conservation and management, which includes sand mining, use of fertilizers and extensive fishing, and non-regulation of the mesh size of fish nets. Raising awareness among the fisherman and strict laws implementation can help to regulate the water quality of the river and also restore the fish diversity.