Flowing through the Mokokchung and Longleng districts of Nagaland, the Dikhu river forms the scenic Tsüla (Dikhu) valley, a popular tourist spot. Today the river, a lifeline for local biodiversity, faces a double whammy of destructive fishing practices and climate change.
A tributary of the mighty Brahmaputra river, Dikhu supports a wide variety of aquatic life, many of which lie at the heart of the Ao and Sumi tribes’ agrarian society. To help preserve indigenous fish species, researchers from Nagaland University have joined hands with native tribes living along the river.
The research team, led by Dr Pranay Punj Pankaj of the Department of Zoology, Nagaland University, in collaboration with the Indian Council of Agricultural Research’s National Bureau of Fish Genetic Resources, studied the reasons behind the falling fish population. Collecting fish samples round the year, they investigated current fishing practices, traditional methods, the level of awareness about conservation and the role of climate change, among other factors.
The study, published in the Journal of Threatened Taxa, recorded 28 fish species across six orders and 13 families. It found that from eco-friendly fishing methods, involving bamboo traps and gill nets, there is an increasing shift towards the use of dynamite, fine-mesh fish nets, electrocution and poisonous chemicals.
Small net, big worry
“When we were small, the fish were big; now we are big, the fish has become small,” a tribal woman lamented to Dr Pankaj during a field visit, referring to the shrinking size of the mahseer (Tor putitora), a freshwater fish that once weighed 10-12 kg. Now, “they are catching mahseers as small as 1-2 kg using small nets. They are only babies. They (tribals) don’t know that the fish can grow up to 17 kg,” Dr Pankaj told businessline, pointing out that such traditional knowledge is no longer passed from one generation to another.
Climate change, too, has played a role in altering breeding patterns and reducing fish population, he added. Additionally, poachers are increasingly active at night, further endangering fish stocks, he said.
River keepers
To reverse the damage and help the river recoup, Dr Pankaj stressed the need for the establishment of a fish sanctuary, similar to a wildlife sanctuary. “Breeding zones need to be mapped. Some areas of the river are better suited for fish breeding. If you destroy that area, then automatically the fish population will reduce,” he said, adding, “Most of the rivers in Nagaland run very fast. Only some areas have stagnant water zones. They can be mapped and included in the ‘greenzones’ to protect the fish ecosystem.”
Moreover, the locals need to be made aware of these developments and guided towards alternative income sources to prevent overexploitation of the aquatic ecosystem, he suggested.
While much of the traditional knowledge may be fading, some conservation ethics remain strong. During a field visit, Dr Pankaj and his team observed a tribal man refraining from hunting a unique bird that crossed his path. Asked why, he replied that the bird was mature and may lay eggs anytime soon; if hunted now, it will hurt the next generation.
The same spirit of ethical hunting must now be directed towards the river’s aquatic life.