Dr. Urzua-Osorio, Angel

Pleuroncodes monodon from the Chilean coast has seasonal reproduction. During the seasonal period, females and their eggs are exposed to seasonal variation in environmental conditions. In P. monodon populations inhabiting the Southern Pacific coast near Concepción, Chile, we quantified late summer (February–March 2014) and late winter (August–September 2014) seasonal variations in female reproductive parameters (carapace length, fecundity, reproductive output (RO), ash weight, organic content) as well as eggs parameters (length, volume, dry weight, organic content). There was conspicuous seasonal variation in the main reproductive parameters of this species. During the summer, the number of eggs and organic content of females were higher than winter, whereas RO was slightly higher in winter than in summer. Significant variation in the size and biomass of the eggs was also found between seasons. For example, eggs laid in summer were smaller, had a lower measured dry mass, and had a lower organic content than eggs laid in winter. Seasonal variations in the fecundity and size of the eggs have implications for fishery models, which can be used to estimate the relative contribution of different cohorts to recruitment and stability of adult benthic populations.

Pleuroncodes monodon is an important fishery resource and key species from the Southeastern Pacific. During its prolonged reproductive period (from February to December), ovigerous females are exposed to seasonal variation in environmental factors (e.g. temperature and food availability), with higher levels of these environmental parameters during summer and lower in winter, and must adjust their biochemistry to ensure their own survival and that of their embryos. The aim of this study was to analyse seasonal changes in the biochemical composition of ovigerous females and their eggs. The data show that the content of lipids, proteins and organic matter in the hepatopancreases of females was significantly higher in winter than in summer. Similarly, the lipid content of the eggs was significantly higher in winter than in summer, yet the protein content of the eggs had the opposite pattern with greater values found in summer. Consistent with the ‘reproductive energetic model’, the initial and final energy produced by the hepatopancreas showed significant seasonal variations, whereas female investment in egg production (in absolute values) did not show significant seasonal differences. The seasonal differences observed in the biochemistry, organic matter and energy content of the female hepatopancreases may be related to the storage of energy for growth and reproduction. Furthermore, the seasonal variation in the content of lipids, proteins and energy in eggs is likely related to embryogenesis and larval hatching in function with environmental conditions. Seasonal variation in the biochemical composition of P. monodon has direct effects on the marine food web and also upon fisheries.