Several fishermen are illegally using commonly available pesticides, particularly synthetic pyrethroids to harvest high-value crustaceans or prawns in the lower stretches of the River Ganga in West Bengal. The practice may cause significant harm to the river’s ecosystem in the long run, scientists from ICAR-Central Inland Fisheries Research Institute (CIFRI) have sounded alarms.
“Research has shown that pesticide residues are present in fish tissues from the River Ganga, although concentrations are currently below levels deemed hazardous to human health.
“However, long-term exposure to these chemicals can impact reproductive health in fish and pose risks to wildlife and human populations dependent on the river for drinking water and livelihood,” the researchers warned, calling for urgent stringent regulatory actions and community awareness. The illegal fishing practice is particularly prevalent in areas extending from Nabadwip to Balagarh in the State, said the study.
Also, as per the representation of the local communities in the studied area, the scientists found that illegal intruders appear from neighbouring areas, specifically the villages adjacent to the river.
“They target the lucrative freshwater prawn (Macrobrachium spp.), which commands high prices in the market. Apart from this, a variety of Small Indigenous Fish species are caught rampantly as the bye catch, including Puntius spp., Gudusia chapra, Salmostoma,” said Ajoy Saha, Archisman Ray, Kausik Mondal, Basanta Kumar Das from ICAR-Central Inland Fisheries Research Institute (CIFRI), Barrackpore, and Vikas Kumar from ICAR-CIFRI, Prayagraj.
Presently, majority of the fish are harvested using gill nets, cast nets, passive fish traps, or occasionally plant-based fish poisons, the banned pesticides are being rampantly used despite being banned.
“Indiscriminate use of synthetic pyrethroids, such as cypermethrin and deltamethrin, disrupts aquatic ecosystems by causing imbalances in fish populations and damaging aquatic flora.
“These chemicals trigger a knock-down effect in crustaceans, leading to their immediate death and impacting other aquatic life forms, the authors said adding that there is an urgent need for stringent regulatory actions and continuous outreach programs to curb the illegal use of pesticides.
“They might also cause mutations in amphibians and insects. Moreover, juvenile fishes are more susceptible to these chemicals, and such detrimental effects on juvenile fishes and reproductive adults may threaten river fish population dynamics. The threat of bioaccumulation looms as birds and otters consume poisoned fish while wild animals drink water from poisoned rivers,” said the study.
“Raising awareness about the harmful effects and enforcing laws against toxic fishing practices is crucial to preserving the Ganga’s ecological integrity.
Also, the scientists suggested that “further research is needed to quantify the extent of pesticide use, its environmental and health impacts, and to develop effective strategies for monitoring and controlling this destructive practice.”
Based on the information gathered from the fishermen, the researchers revealed that there is continuous poaching in the lower and some areas of the upper Hooghly estuary, using pesticides belonging to the synthetic pyrethroid group.
Our study also demonstrated that long-term exposure to cypermethrin, even at an environmentally relevant dose, may affect the reproductive potential of fish. Therefore, fishermen have been warned to be vigilant and avoid eating contaminated fish, noted the authors.
Measures like strict fishing regulations and continuous outreach programmes are necessary to maintain the natural river system, they added.
