As modern fishing methods harm Dikhu River, scientists and communities push for conservation

Nagaland University researchers are collaborating with local communities to study and conserve indigenous fish species in the state’s Dikhu River, integrating traditional ecological knowledge with scientific research to document fish diversity, indigenous fishing techniques, and community-based fishing practices.

The research, led by Dr Pranay Punj Pankaj, Associate Professor of the Department of Zoology, Nagaland University (Lumami Campus), and Metevinu Kechu, a research scholar, was funded by ICAR-National Bureau of Fish Genetic Resources, Lucknow. Their findings were published in the Journal of Fisheries.

The study highlighted that the Ao and Sumi tribes of Nagaland, residing along the Dikhu River, have historically practiced sustainable fishing methods. These include the use of “fasi jal” (gill net), “zutsuk” (cast net), “porki/bulci” (hooks and lines harpoon), “talu tatu” (tubular-shaped traps), and “shiba” (conical-shaped traps), among others.

“Crafts and gears in traditional fishing are typically made from locally available and cost-effective materials such as bamboo and ropes that require less expertise and ease of operation than modern technical equipment. Increasingly, indiscriminate fishing has become a problem in aquatic waters due to modern machinery, while traditional fishing skills and practices are dwindling,” the paper stated.

However, the research team found that villagers are now gradually resorting to destructive fishing methods, including dynamite fishing, electrocution, and chemical poisoning. “The locally produced dynamites are commonly sold in packages of three, with prices ranging from Rs. 350 to Rs. 500. The blast sticks are ignited using a lighter and thrown into the water from a distance to kill big fishes,” the researchers noted. Additionally, synthetic chemicals like lime, bleaching powder, and pesticides are being used to stupefy fish, while electric gadgets powered by charged batteries induce temporary immobilization.

The researchers documented 28 fish species belonging to 13 families and three subfamilies, emphasizing the urgent need for conservation. “The study is significant because the Dikhu River and its fish species have received limited attention in scientific literature. Thus, this study makes a valuable contribution to the body of knowledge on the freshwater ecosystems of northeastern India,” said Dr Pankaj.

The team underscored that destructive fishing techniques pose a major threat to the river’s ecology, which supports a unique and rich biodiversity. The study showed that the Dikhu River is not only vital for local communities but also plays an important role in global conservation efforts.

Unlike many studies, this research utilized seasonal variation in fish diversity and abundance to provide a temporal understanding of how fish populations fluctuate throughout the year. The study identified that the post-monsoon season supports the highest fish diversity and abundance.

“Documenting threatened fish species and their population trends will support targeted conservation efforts,” Dr. Pankaj said. “We need collaborative efforts involving local communities, conservationists, and government authorities to ensure the sustainability of river ecosystems. There is also a need for stricter regulations on destructive fishing methods, habitat protection, and the promotion of traditional, sustainable fishing techniques as part of an integrated conservation strategy.”

Additionally, the researchers recorded the first-ever presence of Garrabirostris, a freshwater fish species previously found in Arunachal Pradesh, Assam, and Bhutan, now documented in Nagaland’s Doyang and Dikhu rivers. This discovery further enriches Nagaland’s ichthyofauna and highlights the ecological significance of these river systems in maintaining biodiversity.

(With inputs from The Deccan Herald and The Statesman)

MT