WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2017 47 measured to obtain the specific growth rate, condition factor (Innis 1990), coefficient of variation, calculated according to Merino et al. (2007). Results and Discussion The final total length and weight of juveniles in the two recirculating systems was similar to each other and greater than that in the static system (Table 3). The specific growth rate of juvenile flatfish cultured in the RAS-L was greater than that cultured in RAS-C or SS (Table 3). Other values for specific growth rate (on weight) reported for this species and other species of flounder include P. adspersus 1.7 percent/d (Silva and Oliva 2010), P. orbignyanus 1.8 percent/d (Sampaio et al. 2001) and Solea spp. 2.1 percent/d (Reig 2001). The length-weight exponent of fish in all systems was around 3, indicating isometric growth (Table 3). In recent years, flatfish culture has been developing in Peru. Carrera et al. (2013) reported the conditioning of broodstock in recirculating aquaculture systems. In the second stage of the project, juvenile culture was carried out at an experimental level at IMARPE laboratories and as a commercial pilot at PDFSA. Different systems have been used to culture flatfish juveniles, such as recirculating aquaculture systems in California flounder (Conklin et al. 2003), semi-recirculation in the Brazilian flounder (Sampaio et al. 2001) and open flow in Senegalese sole (Sánchez et al. 2010). The present research evaluated the growth of P. adspersus juveniles in different culture systems, obtaining a greater growth in recirculating systems than in a static system. Silva and Oliva (2010) obtained an average size of 8.9 cm and a weight and 9.5 g in juvenile culture of P. adspersus. Growth of P. adspersus juveniles was less than that of turbot, which reached 9-10 g in 90-100 DPH (Stoss et al. 2004). An important culture variable is density, which is inversely related to growth rate (Ashley 2007, Kiessling et al. 2007) in flatfish species such as Solea solea (Howell 1998, Schram et al. 2006), Scophthalmus maximus (Irwin et al. 1999) and P. californicus (Merino et al. 2007), among others. In the research reported here, greater growth rate was observed in the RAS, where fish were cultured at a higher density (~ 2-4 kg/m2), than in the static culture system (~ 1 kg/m2). Density has a direct effect on growth variability in flatfish such as turbot, where a more pronounced increase in variation of body weight was found at higher densities (Irwin et al. 1999). The coefficient of variation on fish size was least in the RAS-L than in the other two systems. In the RAS-L, frequent size grading was carried out to reduce size heterogeneity in culture tanks. There were small differences in condition factor of fish cultured in the three systems (Table 3). The condition factor was similar to (CONTINUED ON PAGE 48) FIGURE 6. Water temperature in different culture systems used to culture juvenile Paralichthys adspersus. FIGURE 7. Growth in length (a) and weight (b) of juvenile Paralichthys adspersus in different culture systems. TABLE 3. Biometric information of Paralichthys adspersus juveniles cultured in various culture systems. SYSTEM Parameter Static RAS-L RAS-C Final total length (cm) 7.7 ± 0.2 9.9 ± 0.2 10.5 ± 0.1 Final weight (g) 6.5 ± 0.5 11.4 ± 0.6 15.6 ± 0.6 SGR length (%/d) 0.7 ± 0.1 0.9 ± 0.2 0.7 ± 0.1 SGR weight (%/d) 1.8 ± 0.4 2.7 ± 0.5 2.0 ± 0.2 K 1.33 ± 0.10 1.26 ± 0.01 1.16 ± 0.03 CV weight (%) 40.7 ± 4.1 29.1 ± 1.6 39.4 ± 1.7 b exponent 2.78 3.08 2.94
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