Srinagar: J&K Lake Conservation & Management Authority (LCMA) has informed the High Court of J&K and Ladakh that recent fish kill in Dal Lake was “not unusual” but happens every year due to various environmental factors.
In a report filed in compliance with the directions of court, Vice Chairman LCMA, Dr Bashir Ahmad Bhat, has ,however, not ruled out the possibility of the fish kill due to the presence of pesticide and herbicide in the floating gardens and gardens around the area in it.
The report indicates that hundreds of dead fish were seen floating over the water along fringes of Oberio Ghat, SKICC corners to Nishat Pipe Line Bund (Nishat Basin of Dal Lake) on May 22 this year.
On May 25, the report says, water samples and specimen of small fish (fingerlings) of Crossochellius diplochellus commonly known as Kashmir latia local name Thethur and some specimen of Carassius carassius commonly known as Crucian carp (local name Gang-e-gad) were collected for examination.
While the report underscores that fish kill is difficult to predict even when conditions that contribute to fish are known to exist, it indicates that “fish are incredibly adaptable animal, but for sensitive fish sudden fluctuation in water quality and thermal stratification results in mortality though the tolerance limit of fish vary from species to species.”
The report specifies that the fish kill is an annual phenomenon of natural water bodies and domesticated fish ponds and it may result from a variety of causes -- suffocation due to thermal stratification is the most common.
While the report declares that various other environmental factors such as Pollution, (Ecological Hypoxia) Oxygen Depletion can also be the reason at times, it discloses that this condition may be brought by the Algal blooms, high temperature, diseases, poaching with chemicals, underwater explosion. “Sometimes the causes of many fish kill phenomenon are still unknown. Use of pesticides, herbicides, fertilizers and chemicals alter the chemical parameters of water and also results in fish/fingerling mortality.”
The report indicates that Dal Lake did not encounter any environmental factors like algal bloom and water explosion which could result in fish kill. “The preliminary investigation of the specimen did not indicate any conspicuous characteristic of any known disease in fish”.
The report however underlines that toxicity is a real factor and a very common cause of fish kill and the use of pesticide and herbicide in the floating gardens and gardens around the area cannot be ruled out. “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 University of Kashmir and SKUAST in due course of time”
The report attests to it that “the Prima facie (investigation) indicates that the fish kill may have occurred on 22-23rd May due to thermal stratification as there was a sudden rise in temperature and humidity after many days of cloud cover and rains”.
According to the report, the fish kill are often signs of environmental stress which occurs with rapid fluctuation in temperature or sustained high temperatures, generally cooler water has a potential to hold more oxygen so a period of sustained high temperature can lead to decrease in oxygen level in a water body. “Depleted oxygen levels become the most common cause of fish kill.”
While the report reveals that 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, it indicates: “If a heavy rain or wind occur the layers can mix thereby mixing of water layers that is greater in high oxygen with the waters having low oxygen and thereby reducing the oxygen levels throughout the water column that leads to fish kill instantly.”
The report further reveals that S.K. University of Agricultural Sciences and Technology has been requested for conducting tests for presence of toxicity in Dal-Nigeen waters in order to ascertain use of pesticides, herbicides and weedicides.