Individual cages (8.5 cm diameter x 21 cm high) with mesh walls and plastic bottoms and tops were used to rear postlarvae of the prawn Macrobrachium rosenbergii at 29°C in a recirculating-water system of 2% salinity. Survival rates on adequate diets were near or at 100%. Prawns grew from a mean size of 0.01 g (9 mm postorbital length) to 0.5-0.9 g (30-36 mm) in 12 weeks. Possible heavy-metal toxicity encountered during development of the system is discussed.

Channel catfish of sizes ranging from 0.03 to 0.57 kg and juvenile freshwater prawns (mean wet weight = 0.52±0.40 g) were stocked into four 0.06-ha ponds at densities of 11 120/ha and 4942/ha respectively. The growout period was 132-133 days. At harvest the mean wet weight of the catfish and prawns ranged from 0.63 to 0.72 kg and 33.8 to 42.3 g, respectively. Survival of prawns and catfish was >87% except in one pond where a disease outbreak reduced catfish survival to 70%. Prawn production averaged 172 kg/ha. Approximately 75% of all the harvested prawns had a wet weight that exceeded 30 g. Male prawn populations, composed of three morphotyes (blue claw, orange claw, small), evidenced less variation in wet weight than that previously observed in monoculture populations. Harvesting techniques which permit selective harvest of the prawns appear to be required for practical polyculture.