Fish fauna of the Brahmaputra River, Bangladesh: richness, threats and conservation needs

The Brahmaputra River is one of the largest rivers in the world as well as in Bangladesh. The present study was carried out for a period of one year from January to December 2013 with a view to assessing the availability of fishes in the river with species emphasis on species richness, existing threats and conservation issues. Daytime and night sampling were carried out in three sites located along the upstream to downstream course of the river on a monthly basis. Three fishing gears including cast net, seine net and drag net and one fishing trap were employed to collect fishes. A total of 67 finfish species including 63 indigenous and 4 exotic/alien species have been recorded belonging to 46 genera, 24 families and 8 orders. Cypriniformes and Cyprinidae were the most dominating order (21 species) family (15 species) of native fishes. A small portion (2%) of native fishes was globally threatened. Over one third of total species (38%) were considered threatened to extinct species in Bangladesh. Population trend of over two third of total fish species was Declining in the river. Major threats were alien/invasive species, banned fishing gears and loss of habitats.