Growth and biochemistry of the spiny lobster Sagmariasus verreauxi cultured at low and high density from hatch to puerulus

Stocking density is an important factor affecting the competency of later stage lecithotrophic spiny lobster larvae, yet its influence on biochemical composition has rarely been considered. Biochemical analysis of phyllosoma during ontogeny provides information on the energy storage requirements of late instar phyllosoma and their ability to survive metamorphosis and achieve the energetic demands of the puerulus stage. The current study is the first to examine biochemical composition of spiny lobsters through the entire larval phase. Survival, growth, development, and biochemical composition were measured in Sagmariasus verreauxi phyllosoma that were cultured at High Density (HD) and Low Density (LD) from hatch to puerulus. Protein measured directly by Lowry was considerably lower than crude protein as calculated from nitrogen (N) content using N×6.25, suggesting that a conversion factor of 6.25 was too high. Survival of phyllosoma was significantly higher in the HD treatment after instar 9 due to high mortalities of LD phyllosoma caused by high ozonation during instar 9. However, HD phyllosoma were less susceptible to the high ozonation event possibly due to the larger biomass in HD tanks. Phyllosoma growth and development were more advanced in LD phyllosoma after 108 d. Instar 17 LD phyllosoma were also significantly larger than instar 17 HD phyllosoma. The C:N ratio confirmed proportionally more lipid than protein was accumulated during larval development before a significant decrease in lipid reserves between instar 17 and the puerulus stage by over 21% to fuel the process of metamorphosis and the non-feeding puerulus stage. The study demonstrated the larval phase of S. verreauxi is important for accumulating lipid reserves to fuel metamorphosis and the puerulus stage and provides a more complete picture of the culture requirements of spiny lobsters during ontogeny, particularly for the rarely studied late phyllosoma instars.