The Effect of Vertical Netting and Water Circulation Pattern on Growth and Survival of Penaeus vannamel Postlarvae in an Intensive Raceway System

The growth and survival of Penaeus vannamel postlarvae (PL) were assessed in raceways with different levels of vertical netting and water circulation. Six polyethylene-lined raceways (bottom area 68.4 m²) were stocked with 3,100-1,300 PL/m². Four raceways contained vertical netting-two with 114 m² and two with 1090 m². Aeration was provided from a single air diffuser (26 m long) placed longitudinally at the midline on the bottom. Aeration in raceways without netting (circulated raceways) was provided by four 3-m-long air diffusers and a series of airlift pumps positioned to creat a counterclockwise current around a vertical center wall Differences in survival, final mean weight, harvested biomass, and feed conversion ratio values among treatments were not statistically significant. Pl survival after five weeks in raceways with nettting was 79.8%, compared to 94.8% in the circulated raceways. The average final weight, feed conversion ratio, and yield for the netted raceways were 0.63g, 1.08, and 1.56kg/m², respectively. The corresponding values for the circulated raceways were 0.53g, 1.00, and 1.66kg/m², respectively. Increased surface area provided by vertical netting had no effect upon growth, survival, harvested biomass, and feed conversion ratio of the shrimp. Waste removal was more efficient and less labor intensive in the two raceways with active water circulation.