Spring ichthyoplankton heterogeneity and environmental drivers in adjacent nursery grounds of the Northwest Scotia Sea and Southwestern Atlantic

Abstract

The Yaganes Marine Protected Area (Y-MPA) encompasses a large portion of the Northwest Scotia Sea. Its proximity to important fish nursery grounds in the Southwestern Atlantic, such as the Beagle Channel and the Burdwood Bank, highlights its ecological relevance. This study assessed the composition and spatial variability of ichthyoplankton in the Y-MPA and adjacent areas during austral spring 2022, as well as their relationships with environmental variables. Oceanic waters within the Y-MPA showed low temperatures (< 6 °C) and high salinities (> 34 PSU), whereas nearshore waters (Beagle Channel and Peninsula Mitre) were warmer (> 6 °C) and fresher (minimum 31.29 PSU). Dissolved oxygen concentrations were relatively homogeneous (6 - 7 mL L-1). Three fish egg taxa and eighteen larval taxa were identified. Eggs of Sprattus fuegensis occurred in all zones, while those of Salilota australis and Coelorinchus fasciatus exhibited more restricted distributions. Larval assemblages displayed clear spatial differences: S. fuegensis and S. australis dominated coastal areas, whereas lanternfish (Gymnoscopelus braueri, Krefftichthys anderssoni) prevailed in oceanic waters. Multivariate analyses distinguished two main site groups: the inner Beagle Channel versus all other areas for eggs, and the Y-MPA versus coastal zones for larvae. Redundancy analysis explained 48% of ichthyoplankton variability, revealing strong associations between species distribution and temperature-salinity gradients. Coastal taxa were linked to fresher waters, whereas oceanic taxa were associated with colder, saltier offshore conditions. These findings highlight the Y-MPA’s role for fish early life history stages, particularly S. fuegensis and lanternfish, key wasp-waist species in regional trophic webs.