Hetauda: The fish population and average weight in the famous Kulekhani Reservoir (Indrasarowar) of Makwanpur have been declining in recent years. According to the Kulekhani Fisheries Development Center and Indrasarowar Fish Entrepreneurs Association, the main reason behind the drop is the use of chemical pesticides in the vegetable farms surrounding the lake.
The 7-kilometer-long reservoir, covering an area of around 11,156 cubic meters, currently houses about 400 cages for fish farming. Each cubic meter produces around 4.5 kilograms of fish, said Bikash Balami, Vice-Chairperson of the Fish Entrepreneurs Association. However, both the number and average weight of fish have been decreasing steadily.
Balami explained that chemical fertilizers and pesticides used in nearby vegetable farms get washed into the lake during the rainy season. “When this contaminated water reaches the reservoir, it affects plankton the tiny organisms that fish feed on which directly impacts their growth,” he said.
Fish species like silver carp, bighead, and grass carp which thrive in cold water and depend on natural algae and microorganisms have been particularly affected. The pesticides destroy their natural food sources, reducing both their growth rate and weight, Balami added.
The association has about 650 member families involved in fish farming, sales, and profit-sharing. Income from the fish business also supports local schools and community infrastructure maintenance.
Local hotel owner and fish farmer Purna Thapa Magar said the ecological balance of the lake is deteriorating due to pesticide pollution. “Earlier, fish could grow up to two kilograms, but now they hardly reach 1.5 kilograms,” he said. “Fish from Kulekhani are considered special dishes in local hotels, but their quality and size are no longer the same.”
Fishing has been a major source of livelihood for many communities around the lake. The income supports school operations, road repairs, and community development. However, as fish size and production decline, farmers are now facing financial losses.
According to local youth Sansar Balami from Kulekhani-Kalanki, the Fish Entrepreneurs Association manages fish stocking, care, and sales. “The lake provides jobs to hundreds of local families,” he said. “But as fish get smaller, incomes are dropping, and it’s affecting the local economy too.” He added that fish farming and the lake have also boosted local tourism.
Government Concern and Studies
Manita Paudel, Acting Chief of the Kulekhani Fisheries Development Center, said the reduction in fish weight due to pesticide contamination is a serious issue, and scientific studies are underway. “Recent tests have found higher-than-normal chemical content in the lake water, which may be affecting fish growth,” she said.
The center currently breeds and sells fish species like silver carp, bighead, common carp, grass carp, rohu, naini, bhakur, tilapia, sahar, and katle. About 200,000 baby fish are released into the reservoir every year around mid-September.
Paudel emphasized that maintaining water quality is crucial, as most of the fish produced in Kulekhani are consumed locally. The center has also been running awareness and training programs on water conservation and sustainable fish farming in schools and communities.
Environmental Impact
Commercial vegetable farming is rapidly expanding in Thaha Municipality and Indrasarowar Rural Municipality of Makwanpur. To increase production, farmers often use pesticides like carbofuran, malathion, and dichlorovos, which have long-term effects on soil and water quality.
Saroj Yadav, Head of the Natural Reservoir Fish Promotion and Conservation Center in Hetauda, said pesticides harm both fish and their natural food sources, reducing their survival and growth rates. “Pesticides change the water’s chemical composition, lower egg hatching rates, and damage fish intestines and gills,” he said. “If pesticide runoff continues, it could threaten not only the biodiversity of Kulekhani but also local drinking water and tourism.”
Possible Solutions
Yadav stressed the need to encourage farmers around the lake to adopt organic fertilizers and eco-friendly farming methods. Building filtration ponds or treatment systems to purify water before it enters the reservoir could also help reduce contamination, he added.
