Srinagar: Toxicity caused by the use of pesticides and herbicides in the floating gardens and gardens around Dal Lake can be a reason for the recent mass fish kill in the water body, a report by the Lake Conservation and Management Authority (LCMA) has said.
The report submitted before the J&K High Court about the recent mass deaths of fish in the Dal Lake read “toxicity is a real factor and a very common cause of fish kill, the use of pesticide common cause of fish kill, the use of pesticide and herbicide in the floating gardens and gardens around the said area cannot be ruled out”.
The report submitted by Bashir Ahmad Bhat, Vice-Chairman LCMA, said: “Some of the pesticides and herbicides reportedly used contain chlorpyriphos, which is a potent contact poison. The levels of toxic elements in water and biological magnification if any in the food chain needs an elaborate and detailed study which can be taken up with the University of Kashmir and SKUAST in due course of time.”
Prima facie, the report said, indicates the fish kill may have occurred on 22-23rd May 2023 due to thermal stratification as there was a sudden rise in temperature and humidity after many days of cloud cover and rains.
Fish kills, it said, are often signs of environmental stress which occurs with rapid fluctuation in temperature or sustained high temperatures. Generally, cooler water has the potential to hold more oxygen so a period of sustained high temperature can lead to a decrease in oxygen level in a water body.
Depleted oxygen levels become the most common cause of fish kill, it further said, adding a short period of hot weather increases the temperature in the surface layer of water and the warmer water tends to stay near the surface.
According to the report, if a heavy rain or wind occurs, the layers can mix — mixing of water layers high in oxygen with the waters having low oxygen — thereby reducing the oxygen levels throughout the water column that leads to fish kill instantly.
The sites, the report said, are still under observation and samples will be analyzed and oxygen levels shall be constantly monitored also at the adjacent sites too for any clue pointing toward fish mortality.
The observation and preliminary investigation of water quality and site survey, the report stated, showed that water had an odour that may be attributed to the decomposition of specimens at sites of the fish kill. The water clarity and colour was normal on 25th of May when sampling of the site was done.
The fish kill, the officer claimed, is an annual phenomenon of natural water bodies and domesticated fish ponds. It may result from a variety of causes; the most common cause is suffocation due to thermal stratification, his report stated.
“Various other environmental factors such as pollution, (ecological hypoxia) and oxygen depletion can also be the reason for the fish kill at times. This condition may be brought by algal blooms, high temperatures, diseases, poaching with chemicals, underwater explosions, etc. Use of pesticides, herbicides, fertilizers, and chemicals alter the chemical parameters of water and also results in fish/fingerling mortality,” read the report.
Trying to pacify the public, the report said the fish kill phenomenon of May 2023 was at a few sites of Nishat Basin of Dal Lake only where the quantity of dead fish isn’t alarming as such because it was restricted to a few pockets of the lake only. The preliminary investigation of the specimen did not indicate any conspicuous characteristic of any known disease in fish.
The fish kill, according to Dal dwellers, was an unusual event.
Abdul Aziz Tiploo, a 60-year-old fisherman, said that he has no memory of any such massive kill since his adulthood. It was something astonishing and incredible, he said.
