18 SEPTEMBER 2015 • WORLD AQUACULTURE • WWW.WAS.ORG Intensive production of shrimp is getting increased attention worldwide as a potential means to improve aquaculture production through application as a transitional nursery system between the hatchery and growout ponds (Correia et al. 2014). The use of nurseries for shrimp culture is on the rise because a nursery phase contributes to rapid growth. In addition, it is possible to manage higher stocking densities to reduce unit production cost, potentially increase the number of annual crops though reduced duration of grow-out, head start production in cooler months in controlled temperature systems, and provide disease control and increased survival at the end of the nursery period. However, high stocking densities in nurseries may decrease growth and survival of shrimp because of decreased available space, the availability of natural food, cannibalism, degradation of water quality and accumulation of organic matter on the tank bottom (Nga et al. 2005, Arnold et al. 2006). It is not known if high stocking densities in shrimp culture with clearwater recirculation produces similar results to those reported in the literature because several nursery systems used involve high microorganism concentrations (biofloc) and some have been managed poorly. Furthermore, failure in water oxygenation could impact shrimp postlarvae performance in nursery tanks. This article describes a study that investigated the performance of Litopenaeus vannamei postlarvae reared in indoor nursery tanks at different stocking densities in a clearwater recirculation system. Clearwater Recirculating System and Experimental Design Experiments were performed in indoor tank facilities of the Marine Aquaculture Station Prof. Marcos Alberto Marchiori (EMA) of the Federal University of Rio Grande, Brazil. The effects of stress caused by population density were evaluated in a clearwater recirculating system of indoor shrimp nursery tanks. This system was used because the main objective of the study was to determine the productive performance of shrimp postlarvae in terms of tolerance to crowding and to maintain the same water quality to detect the maximum stocking density for the nursery phase. The system included twelve 0.15m3 circular tanks with a bottom area of 0.5-m2 diameter that were provided with diffused aeration (Fig. 1). A biological filter, consisting of two 100-L tanks filled to 40 percent with 1-inch Bio-Balls and provided with intense aeration, was placed in a 4-m3 matrix tank. Each experimental tank was supplied by water pumped from the matrix tank. A submersible pump distributed water to tanks and Intensive Nursery Production of Litopenaeus vannamei Postlarvae in a Clearwater Recirculating System Héctor M. Esparza-Leal, Alessandro Pereira Cardozo and Wilson Wasielesky, Jr. FIGURE 1. Experimental tanks (0.15 m3) used to evaluate culture performance of Litopenaeus vannamei postlarvae at different stocking densities in a clearwater recirculation system. LEFT, FIGURE 2. Water quality in the matrix tank and culture tanks used to grow Litopenaeus vannamei postlarvae at different stocking densities in a clearwater recirculation system. RIGHT, FIGURE 3. Growth and survival of Litopenaeus vannamei postlarvae reared in a clearwater recirculation system at different stocking densities for 42 days. Different letters indicate significant differences (P < 0.05; ANOVA, Tukey´s test).
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