Seasonal patterns of Patagonian sprat Sprattus fuegensis early life stages in an open sea Sub-Antarctic Marine Protected Area

The Patagonian sprat Sprattus fuegensis is a species of ecological importance in the Southwest Atlantic Ocean. However, information regarding S. fuegensis in the Namuncura Marine Protected Area-Burdwood Bank (NMPA-BB), an open sea Sub-Antarctic Marine Protected Area located in the Argentinian shelf, is outdated and fragmented. Understanding the dynamics of species inhabiting the NMPA-BB is relevant to establish future adequate management strategies. We assessed the abundance, size, and development of S. fuegensis early life stages during spring, summer, and autumn in order to evaluate their seasonal patterns. Compared to neighboring areas, S. fuegensis was particularly abundant in the NMPA-BB, which can be considered a major spawning and nursery ground. Within the NMPA-BB, abundances tend to be higher at the center, probably as a result of the marine currents. Eggs were only recorded in spring, while larvae were recorded in all seasons sampled, with maximum abundances occurring during spring. Larger larval sizes and more developed stages occurred in summer and autumn. Analysis of otolith microstructure showed that spawning periods take place between October and March, peaking in November. Slow growth rates (maximum of 0.30 mm day(-1)) and prolonged larval phase would respond to the low temperatures recorded in the NMPA-BB. Additionally, marked monthly differences in otolith growth would suggest a seasonal effect on the developmental patterns of S. fuegensis larvae. Future studies will be necessary to completely understand S. fuegensis development and determine its trophic role in the NMPA-BB.