Fluctuation of temperature, bio-security, water hardness and disruption of power supply are the major challenges to substantial reduction of mortality rate, says an expert
Farmers are increasingly becoming interested in cultivating prawns in freshwater in Rajshahi, as for the first time, the state-owned hatchery has gone into operation this year producing around 300,000 larvae.
There is potential for freshwater prawn farming in Rajshahi. Although prawn larvae production is the most challenging task, if larvae can be made readily available, it will take prawn farming in Rajshahi to the next level, said Dr Jinnat Ara Rokeya Chowdhury, manager of Fish Seed Multiplication Farm.
“Maintaining biosecurity in prawn hatcheries by minimizing risk factors and the presence of pathogens and their potential dispersion is key to good egg yield and post-larvae production of eggs. Prawns go through eleven larval stages before metamorphosing to become post-larvae. During this period, balanced nutrition, optimum water temperature, suitable water quality and ventilation must be strictly maintained. Any sudden changes in temperature can cause mortalities when prawns are stocked,” she added.
She said mother prawns were collected from the Kocha River in Pirojpur district on May 23 last. Subsequently, those were disinfected and nursed in brine collected from the coastal belt.
During the entire nursing period, bio-security has been maintained strictly as it is very important for post-larvae production from the larval stage.
“We got the huge larvae from May 25 to 29 in phases through maintaining balanced food, temperature, aeration and suitable water quality stringently,” Dr Jinnat said, adding that around 30 percent survival rate had been attained in this initiation year.
Around 100,000 post-larvae were supplied among farmers in different districts under Rajshahi division this year.
Post-larvae will continue to be produced here by bringing parents from the saline rivers every breeding season. Farmers can purchase healthy and quality hatchlings from here at a reasonable price. As a whole, the hatchery will contribute a lot towards fulfilling the farmers’ demand.
She highlighted the fluctuation of temperature, bio-security, water hardness and disruption of power supply as major challenges to a substantial reduction of the mortality rate.
Abdus Sobhan, a farmer in Kathalbaria village under Paba upazila, said many farmers collected juvenile prawns from him. Within six months, each of those becomes 120 to 125 grams in weight. In local markets, prawns are now being sold at Tk700 to 750 per kilogram.
Farmer Shihab Uddin of Shilinda area said prawn farming was gaining popularity but supply of post-larvae was inadequate.
He said steps should be taken to reduce the price of prawn seed and quality feed. Prawn production in the existing hatchery should be increased.
Speaking on the matter, District Fisheries Officer Alok Kumar Saha said: “There is potential for freshwater prawn farming in Rajshahi and many farmers are into such farming. So we are advising these farmers as a way of helping them take their farming to the next level.”
“The fisheries department intends to expand prawn farming in freshwater bodies by transferring and disseminating updated technologies to grassroots farmers. Demands for hatchlings and fingerlings will be met through successful implementation of the projects,” said DoF Divisional Director Tofaz Uddin.
In addition to motivating farmers,, the department had set up projection ponds. The farmers should cultivate shrimp by using modern shrimp farming methods as it was a very profitable fish farming sector, he added.