Guru Angad Dev Veterinary and Animal Sciences University (GADVASU) organised a session on how to care for fish during the winter on Tuesday. Meera D Ansal, a scientist from the College of Fisheries, GADVASU spoke on the occasion.
“During winters, temperature of surface water is colder than the bottom layers and the fish prefers to live in the bottom zone. Breeders should ensure that water is up to 6 feet deep so fish get enough space for hibernating in the warmer bottom zone. In shallow waters, the whole water column becomes cold, which affects the fish and can prove fatal. Regular addition of tube well water at dusk helps in keeping the surface water warm,” said the expert.
Reduced length of day and light intensity affects oxygen levels in ponds due to decrease in the process of photosynthesis, she said.
“The situation is aggravated during cloudy days. The farmers are advised to aerate their ponds either by adding fresh water or by using aerators, especially during early hours of the day. Regular monitoring of water pH is also needed during cloudy days in winters, which may even fall to harmful levels due to poor photosynthetic activity and result in higher carbon dioxide levels in the pond,” said Ansal.
She also stated that feed intake of fish decreases with the fall in temperature as its digestive system becomes sluggish.
“Hence, it is essential to reduce the feeding rate by 50-75% depending on the temperature. In case the temperature falls below 50°C, stop feeding them. Excess feed remains unconsumed and accumulates at the pond bottom, which results in deterioration of quality of water,” she said.
It is also necessary to reduce/stop adding organic manures like cow dung, poultry droppings and pig dung in the pond as rate of decomposition of organic manures declines due to poor microbial activity during winters, she said.
“Presence of algal blooms is another serious problem during winters as they block the penetration of sunlight in to the water. Algal blooms appear due to the presence of excess nutrients in the water. Hence it is also recommended to avoid excessive use of inorganic fertilizers during winters,” she said.