Ichthyoplankton temporal and spatial patterns in sub-Antarctic coastal and oceanic waters of the Southwestern Atlantic

Abstract

The southernmost region of the Southwestern Atlantic (SW Atlantic) has a complex environmental structure with different oceanographic conditions that aid the survival of early life stages of sub-Antarctic fish. This study evaluated the spatial and temporal variations in ichthyoplankton composition of SW Atlantic's sub-Antarctic coastal and oceanic waters and the relationship with environmental variables (water temperature and salinity). Six multidisciplinary oceanographic surveys (austral spring of 2014, 2015, 2016, summer of 2015, and autumn of 2016, 2017) were conducted in two coastal and three oceanic zones of the southern SW Atlantic. A total of 425 fish eggs and 871 fish larvae at the yolk sac (N = 37), preflexion (N = 513), flexion (N = 13), and postflexion (N = 308) stages were collected. Eleven fish taxa in the larval stage were identified. The highest abundance of eggs and larvae in the preflexion stage occurred in spring, dominated by the Fuegian sprat (Sprattus fuegensis) in all zones. However, the abundance of fish larvae in the postflexion stage was higher in autumn at the southern slope of the Burdwood Bank, with a dominance of Patagonian cods (Patagonotothen spp.). Water temperature played a significant role in explaining the abundance of larvae in the preflexion stage, whereas water salinity was significant for eggs and larvae in the postflexion stage. Our results allow us to infer the role of this complex oceanographic system in the early life history of fish. Thus, a conceptual framework for the ichthyoplankton distribution patterns in the area is proposed.