Giant Freshwater Prawn

The ideal pond size for commercial freshwater prawn farming ranges from 0.2 to 2.0 hectares. Smaller ponds (0.2-0.5 ha) are easier to manage and harvest, while larger ponds (1-2 ha) are more economically efficient. Pond depth should be maintained at 1.2-1.5 meters with proper slope for drainage.

Macrobrachium rosenbergii typically reaches market size (30-50g) in 4-6 months under optimal conditions. Males grow faster and can reach 100g in 6 months. The culture period depends on stocking density, feed quality, water temperature (28-31°C optimal), and management practices.

For grow-out ponds, the recommended stocking density is 20,000-40,000 post-larvae (PL15-20) per hectare for semi-intensive culture. In intensive systems with aeration, densities can reach 60,000-80,000/ha. Lower densities (15,000-20,000/ha) produce larger prawns but lower total yield.

Optimal water parameters include: Temperature 28-31°C, pH 7.0-8.5, Dissolved Oxygen >5mg/L, Alkalinity 80-120mg/L, Hardness >40mg/L (calcium important for molting), Ammonia <0.1mg/L, Nitrite <0.5mg/L, and Salinity 0-5ppt. Regular monitoring is essential for success.

Initial investment for 1-hectare prawn farm: Pond construction (LKR 300,000), Post-larvae 30,000 nos (LKR 120,000), Feed for 5 months (LKR 450,000), Aeration equipment (LKR 150,000), Shelter nets (LKR 50,000), Labor & misc (LKR 130,000). Total: LKR 1,200,000. Expected revenue: LKR 2,000,000-2,400,000 per cycle.

Prawns require high-protein feed (30-35% for grow-out, 40% for juveniles). Use sinking pelleted feed 2-4mm size. Feed ingredients include fish meal, soybean meal, wheat flour, vitamins, and minerals. Feed 5-10% body weight for juveniles, 3-5% for adults, distributed 2-3 times daily. FCR typically ranges from 1.8-2.5.

Provide adequate hiding places using PVC pipes, bamboo, or nets. Maintain proper calcium levels (>40mg/L) for successful molting. Stock similar-sized prawns, ensure adequate feeding, maintain optimal density, and practice selective harvesting of larger males. Shelter structures can reduce cannibalism by 30-40%.

Common diseases include White Muscle Disease (Idiopathic Muscle Necrosis), Black Gill Disease (environmental stress), Bacterial infections (Aeromonas, Vibrio), and parasites (Vorticella, Zoothamnium). Prevention through good water quality, proper nutrition, avoiding overcrowding, and regular health monitoring is key.

Yes, prawns can be successfully cultured with compatible fish species. Suitable combinations include prawns with tilapia, catfish, or carps. Stock prawns first (20,000/ha) then add fish (2,000-3,000/ha) after 30 days. This system utilizes different pond niches and can increase total productivity by 20-30%.

Freshwater prawns have excellent market demand both locally and for export. Current farm gate prices range from LKR 600-900/kg depending on size (larger prawns fetch premium prices). Export quality prawns (>50g) can reach LKR 1,200/kg. Local hotels, restaurants, and supermarkets are primary buyers.

NAQDA provides: 50% subsidy for pond construction (up to LKR 600,000), subsidized post-larvae from government hatcheries, free technical training, water quality testing services, disease diagnosis support, and assistance in obtaining bank loans at 4-6% interest rate. Contact your nearest NAQDA regional office for details.

Use selective harvesting with cast nets or traps every 2-3 weeks to remove larger males (>50g), reducing competition. For complete harvest, drain pond partially and use drag nets. Harvest early morning when temperature is cool. Immediately ice harvested prawns. Selective harvesting can increase total yield by 15-20%.