"Though the Northeast is endowed with a large number of rivers, wetlands, lakes and ponds, various species of fishes in the region are facing the threat of extinction," states a bulletin issued by the Central Inland Fisheries Research Institute.
"There is a general perception that the rich fish fauna of the region have been considerably depleted over the years, a major indicator of which is declining catches from rivers and other natural open water bodies," as per the bulletin.
"Certain fish species like osteobrama belangeri, pithia, butter catfish, clown knife fish (chitala), Bengala elenga, punga (pangasius), etc. are increasingly becoming rare," the bulletin says.
According to scientists, there are 267 fish species belonging to 114 genera under 38 families and 10 orders in the region.
The International Union for Conservation of Nature and Natural Resources (IUCN) has stated that six fish species in the Northeast are critically endangered, 31 endangered and 46 species found vulnerable, indicating that they face high risk in the future.
Most of the major fishes caught from the open water bodies are juveniles of major carps (catla, rohu, mrigal and kalbasu), indicating that they are caught before attaining adulthood.
"Commercial fishing in most open water fisheries are now dominated by small-sized miscellaneous fishes in place of major carps and large catfishes," the bulletin says.
"The fact that as many as 83 out of the 105-odd species evaluated were found to be threatened indicates that many fish species of this region face a serious threat of extinction," the paper warns.
"Arguably, the total number of threatened fish species of the region will be much higher once the conservation status of all the species is evaluated," it says.
The bulletin suggests prevention and control of aquatic pollution and siltation of rivers, wetlands, reservoirs through soil conservation and afforestation.
The paper also says, "Construction of multipurpose river valley projects should be done with abundant caution. Even if such projects become unavoidable, adequate safeguards including fish passes should be provided to minimize adverse effects on migratory fish species."
Identification and protection of breeding grounds of commercially important fishes and allowing free migration up and down rivers and to associate wetlands and vice versa for spawning and feeding, besides protection of brood stock and juveniles are the other measures suggested.
The bulletin also calls for 'fishing holidays' during the monsoon to ensure the success of spawning and banning or phasing out of destructive fishing methods like mosquito nets, dewatering, use of explosives and community fishing for conservation of fish stocks.