12 September 2009 , c = -0.03, and d = 7.5x10-4 for 3395 crabs/m2, b = -4.69, c = 0.14, and d = -3.7x10-3 for 6791 crabs/m2, b = -3.46, c = 0.03, and d = 4x10-5 for 13581 crabs/m2. Productivity (number of juveniles/m2) was calculated by multiplying number survivors at 28 days post metamorphosis by stocking density. A response curve was used to find optimum stocking density during juvenile culture: productivity (%) = 1.065 x SD – 4.13x10-5 x SD2 (Figure 5), which optimum is 12900 crabs/m2. The effect of diet on juvenile carapace width was modeled using linear models Juvenile CW (mm) = a + bx (Figures 4), where a= 1.0238 and b= 0.077 for NHA, a= 1.1462 and b= 0.0422 for Amphora, a= 1.0299 and b= 0.0686 for FNHA, a= 0.9505 and b= 0.0596 for CP, a= 1.0111 and b= 0.0971 for NHA + Amphora, a= 1.0361 and b= 0.0781 for NHA + FNHA, a= 0.9967 and b= 0.0633 for NHA + CP. The time to achieve commercial size (1 cm) was estimated based on these models (Figures 4): 117, 210, 131, 152, 93, 115, and 143 days for NHA, Amphora, FNHA, CP, NHA + Amphora, NHA + FNHA, and NHA + CP, respectively. Consult sidebars and Penha-Lopes et al. (2007) for further details. The larval and juvenile survival and growth models developed suggest the use of a different protocol. By using a stocking density of 60 larvae/L and a prey density of 10 Artemia nauplii/mL during larval culture, and a diet that combines newly hatched Artemia and Amphora microalgae and Fig. 5. Effect of stocking density on juvenile culture. 12,900 juveniles/m2 during juvenile culture we were able to considerably improve the productivity of Mithraculus forceps culture (Table 1). Ornamental aquaculture has been recognized as the best solution to minimize wild harvest from coral reef ecosystems, allowing a sustainable growth of the marine aquarium industry (Cato and Brown 2003). The models developed, besides being a very useful tool for production prediction, contributed to the improvement of productivity. Productivity models should be developed and provided to the producers to select the optimal conditions to culture target species (Figueiredo and Narciso 2006). By increasing productivity of aquacultured species, we can decrease the demand for wild harvested animals and protect natural environments. However, protocols still require adjustment for mass-scale culture and optimization combining bio-productive and economic predictors through modeling to maximize profitability. Notes 1Laboratório Marítimo da Guia, Faculdade de Ciências da Universidade de Lisboa, Estrada do Guincho, 2750-374 Cascais, Portugal. (Email: joana_figueiredo@portugalmail.pt. Acknowledgment Thanks to Justin Anto, Junda Lin, Luís Narciso and Gil Penha-Lopes for their help and constructive criticism. The author also thanks Fundação para a Ciência e a Tecnologia (FCT) and Portuguese Government for financial support (scholarship #SFRH/BD/17130/2004). References Calado, R., L. Narciso, S. Morais, A. L. Rhyne and J.Lin. 2003. A rearing system for the culture of ornamental decapods crustaceans larvae. Aquaculture 218: 329–339. Cato, J. C. and C. L. Brown. 2003. Marine Ornamental Species: Collection, Culture and Conservation. Part III— The Invertebrates. Iowa State Press, United States. Figueiredo, J. and L. Narciso. 2006. Productivity improvement of Lysmata seticaudata (Risso, 1816) larval rearing protocol through modelling. Aquaculture 261: 1249–1258. Figueiredo, J., L. Narciso, R. Turingan and J. Lin. In press. Efficiency of using emerald crabs Mithraculus sculptus (Lamarck, 1818) to control bubble alga Ventricaria ventricosa (sin Valonia Mithraculus forceps adults (photographed by Gil PenhaLopes)
RkJQdWJsaXNoZXIy MjExNDY=