Otolith chemical composition suggests local populations of Antarctic silverfish Pleuragramma antarctica (Boulenger, 1902) around Antarctica are exposed to similar environmental conditions at early life stages

The Antarctic silverfish Pleuragramma antarctica is a key species in the Southern Ocean ecosystem, and it is potentially threatened by the climate change affecting Antarctic ecosystems. Assessing the possible exposure to similar or different environmental conditions at early life stages and gathering information about connectivity or segregation between local populations of P. antarctica can be key for planning sound management strategies for this species. By using Laser Ablation Inductively Coupled Plasma Mass Spectrometry, we characterized the otolith chemical composition of 163 adult Antarctic silverfish collected from three areas located thousands of kilometers apart from each other: Cape Hallett, Adelie Land, and Joinville Island. Otoliths were analyzed for chemical composition of both the edge (reflecting the exposure of individuals to environmental conditions at the site where they were sampled) and the core (reflecting exposure to environmental conditions during early life periods after the egg fertilization). We found that the chemical composition along otolith edges was heterogeneous between samples collected at Joinville Island and those collected at the other two sampling areas. In contrast, the chemical composition of otolith cores was homogenous. Our study suggests that adult Antarctic silverfish inhabiting areas very distant from each other have been exposed to similar environmental conditions at early life stages, and could have experienced similar growth rates and physiological processes. This would imply that environmental drivers probably do not play a role in determining potential spatial variability in individual fitness at early life stages, and should not have a major impact on population replenishment.