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To reap maximum benefit of the fish growing season in Punjab, extending from April to November, it is vital to take care of the stock during the summer season to protect it from temperature exceeding 350C. Communicating her views, Dr. Meera D. Ansal, College of Fisheries of Guru Angad Dev Veterinary & Animal Sciences University, Ludhiana, emphasized that farmers shall maintain 5-6 feet water depth in their ponds. It will provide sufficient comfortable zone to the fish below the surface layer, which gets heated up beyond optimum temperature range (28-320C) during the summer months.
Further, she informed that ‘Oxygen’ is the most important issue to be addressed, which may fall to lethal levels, especially during dawn, due to enhanced biological activity in the pond. Hence, aerate the ponds during early hours of the day before sunrise, either by adding fresh water or by aerators. High oxygen content will keep the fish healthy and increase its food converting efficiency. If disease outbreak and fish gasping air at water surface is observed, provide aeration, add fresh water and also suspend manuring and feeding to improve the water quality. Nutrient rich pond water can be used to irrigate the paddy fields during this time and fresh water can be added in the fish ponds. It will improve water quality in the pond and reduce fertilizer requirement of the paddy crop as well.
It is very important to sustain regular plankton (natural fish food) production in the pond and provide a nutritionally balanced supplementary diet, so as to achieve optimized production targets. Keep the pond rich in plankton through mixed utilization of organic manures and inorganic fertilizers. Algae grow very fast during summers and nutrient enrichment leads to formation of algal blooms or mats. Manuring/fertilization of pond shall be suspended in case water turns dark green, dark brown or greenish brown in colour and a green, brown or sometimes red coloured algal mat appears on the water surface. Farmers also need to check day-night variation in water pH, which may cross 9.5 during peak day hours and fall below 7.5 during night hours, due to excessive growth of algal blooms in the pond. Regular bottom racking with the help of barbed wire is recommended to prevent accumulation of toxic gases like ammonia and carbon dioxide in the pond. Toxicity of ammonia in fish ponds increases with increase in temperature and pH, which can be reduced by keeping the ponds well aerated and adding a dose of gypsum/alum as per expert advice.
Farmers shall refrain from anticipating higher production through increased input in terms of seed, feed and manure/fertilizer. It not only enhances input cost, but also leads to crop failure due to oxygen depletion during summers.
Adhering to the golden rule of “Prevention is Better than Cure’ for disease management, Dr. Meera advised to the farmers to follow the recommended prophylactic measures with lime, potassium permanganate or ‘CIFAX’, so as to maintain fish health and case of disease occurrence, consult an expert for diagnosis and treatment.
