WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2015 19 Total ammonia concentration did not exceed 1.5 mg/L. Good water quality in all tanks was maintained because of the high recirculation rate between experimental tanks and the matrix tank (recirculation rate ≈ 20 times per day). This study demonstrated that good growth, survival and production in the nursery phase of shrimp can be obtained using a clearwater recirculation system. Notes Héctor M. Esparza-Leal, Departamento de Acuacultura, Instituto Politécnico Nacional-CIIDIR Unidad Sinaloa, Boulevard Juan de Dios Bátiz Paredes # 250, Guasave, Sinaloa 81101, Mexico and Post-doctorate Fellow, Universidade Federal do Rio Grande, Instituto de Oceanografia, Laboratório de Carcinocultura. Rua do Hotel, 02, Praia do Cassino, Rio Grande, Estado do Rio Grande do Sul, Brazil, CEP 96210-030 Corresponding author: Tel.: +52 687 8729626; fax: +52 6878729625. E-mail: hesparza@ipn.mx Alessandro Pereira Cardozo and Wilson Wasielesky, Jr., Universidade Federal do Rio Grande, Instituto de Oceanografia, Laboratório de Carcinocultura. Rua do Hotel, 02, Praia do Cassino, Rio Grande, Estado do Rio Grande do Sul, Brazil, CEP 96210-030 1 Coralife®, 5401 W. Oakwood Park Drive, Franklin, WI 53132 USA 2 Model 556 MPS, YSI Inc., Yellow Springs, OH, USA References APHA (American Public Health Association). 1998. Standard Methods for the Examination of Water and Wastewater. 20th edition, Washington, DC, USA. Arnold, S.J., M.J. Sellars, P.J. Crocos and G.J. Coman. 2006. Intensive production of juvenile tiger shrimp Penaeus monodon: An evaluation of stocking density and artificial substrates. Aquaculture 261:890-896. Correia, E.S., J.S. Wilkenfeld, T.C. Morris, L.W. Wei, D.I. Prangnell and T.M. Samocha. 2014. Intensive nursery production of the Pacific white shrimp Litopenaeus vannamei using two commercial feeds with high and low protein content in a biofloc-dominated system. Aquacultural Engineering 59:4854. Nga, B., M. Lurling, E. Peeters, R. Roijackers, M. Scheffer and T. Nghia. 2005. Chemical and physical effects of crowding on growth and survival of Penaeus monodon Fabricius post-larvae. Aquaculture 246:455-465. Sokal, R.R. and F.J. Rohlf. 1969. Biometry. Principle and Practices of Statistics in Biological Research. W.H. Freeman, San Francisco, USA. Strickland, J.D.H. and T.H. Parsons. 1972. A Practical Handbook of Seawater Analysis. Fish Research Board of Canada Bulletin, Ottawa, Canada. UNESCO (United Nations Educational, Scientific and Cultural Organization). 1983. Chemical Methods for Use in Marine Environmental Monitoring. Manual and Guides. Intergovernmental Oceanographic Commission, Paris, France. this water returned via gravity to a drain directed to the matrix tank. Water was completely recirculated about 20 times each day (flow rate ≈ 2.1 L/min/tank). The system was filled with water pumped from a nearby beach and filtered through a sand filter and a 5-µm pore cartridge filter. There was no renewal of water during the study, only replacement of water lost by evaporation with dechlorinated freshwater. Water temperature was maintained with two heaters immersed in the matrix tank. The photoperiod for the experimental room was 12/12 h light/dark cycle, with 200 lux intensity at the water surface provided by artificial lighting. Shrimp nauplii were obtained from a commercial hatchery (Aquatec Ltda., Canguaretama, Rio Grande do Norte, Brazil) and maintained in the EMA hatchery until reaching post-larval stage PL25. These post-larvae (mean initial weight = 9 ± 2 mg) were stocked into experimental tanks at 1500, 3000, 6000, and 9000 PLs/m3. There were three replicate tanks for each stocking density. Shrimp were fed twice daily at 0800 and 1600 h with a commercial, 40 percent protein feed for 42 days. Feeding rate was adjusted daily according to consumption. During the study, physicochemical parameters were monitored in the matrix tank and experimental tanks. Dissolved oxygen concentration, temperature, pH and salinity were monitored twice daily at around 0800 and 1600 h with a multi-parameter analyzer.2 Concentrations of total ammonia (NH3+NH4 +), nitrite, nitrate and phosphate were measured weekly (UNESCO 1983). Total suspended solids and alkalinity were determined weekly (Strickland and Parsons 1972, APHA 1998). Shrimp growth was determined by weighing 50 shrimp from each experimental tank individually on a digital balance every week. Shrimp were returned to tanks after weighing. At the end of the study, shrimp that survived in each experimental tank were weighed and counted to evaluate growth (final weight, specific growth rate), survival, feed conversion ratio and tank production. Shrimp biological performance and water quality parameters were analyzed with a one-way analysis of variance for a completely randomized design and with a Tukey test (Sokal and Rohlf 1969) when a significant difference was detected among treatments. Differences were considered significant at 95 percent. Results An inverse relationship between stocking density and growth was observed. Shrimp growth was best at lower densities, with growth of 11.8 percent/d at 1500 PLs/m3 and 10.8 percent/d at 3000 PLs/m3. There were significant differences between lower densities of 1500-3000 PLs/m3 and higher densities of 6000-9000 PLs/m3. There were no differences between treatments at the highest stocking densities (6000 and 9000 PLs/m3). Production was significantly different among treatments with a similar trend to shrimp growth. Final biomass increased with stocking density, ranging from 1.4 to 4.1 kg/m3. Shrimp survival was good in all treatments (85 to 92 percent) and there were no significant differences in survival among stocking densities between 1500 to 9000 PLs/m3 (Fig. 2). Feed conversion was also not significantly different among density treatments, ranging from 0.9 to 1.2. The measured physicochemical parameters were not different between treatment tanks and the matrix tank (Fig. 3).
RkJQdWJsaXNoZXIy MjExNDY=