The effect of stocking density on growth, metabolism and ammonia-N excretion during larval ontogeny of the spiny lobster Sagmariasus verreauxi

Stocking density is a critical factor affecting performance of aquatic organisms in culture, however, its influence on energy utilisation has rarely been considered. Energy partitioning is particularly important for spiny lobster phyllosoma, which must accumulate sufficient energy reserves for metamorphosis and the nonfeeding puerulus stage. The current study is the first to examine the energetics of spiny lobsters throughout the entire phyllosoma phase and determined the physiological influence of density. Growth and development, oxygen consumption and ammonia–N excretion rates were measured in Sagmariasus verreauxi phyllosoma that were cultured at High Density (HD) and Low Density (LD) from hatch to puerulus. Phyllosoma growth and development was more advanced in LD phyllosoma after 108 day in culture and mass of LD instar 17 phyllosoma was greater. There were no differences in routine metabolic rate (R_r) and ammonia–N excretion of phyllosoma between densities. However, the O:N ratio decreased in final instar phyllosoma demonstrating a shift towards higher protein catabolism. Routine metabolic rate also increased in late stage phyllosoma, possibly due to higher energy requirements in preparation for metamorphosis and increased swimming activity. The R_r of spiny lobster larvae was significantly lower than that of other crustacean larvae, which may be a characteristic of their extended larval phase, slower growth rate, and larger body size. The study demonstrated late stage phyllosoma have higher weight specific energy requirements than the preceding larval stages and exhibit a metabolic shift towards protein catabolism, suggesting an increased importance of storing lipid as an energy reserve for the puerulus stage.