Testing early life connectivity using otolith chemistry and particle-tracking simulations

We measured the otolith chemistry of adult Scotia Sea icefish (Chaenocephalus aceratus), a species with a long pelagic larval phase, along the Antarctic Circumpolar Current (ACC) and compared the chemistry with simulated particle transport using a circulation model. Material laid down in otolith nuclei during early life showed (i) strong heterogeneity between the Antarctic Peninsula and South Georgia consistent with a population boundary, (ii) evidence of finer-scale heterogeneity between sampling areas on the Antarctic Peninsula, and (iii) similarity between the eastern and northern shelves of South Georgia, indicating a single, self-recruiting population there. Consistent with the otolith chemistry, simulations of the large-scale circulation predicted that particles released at depths of 100-300 m on the Antarctic Peninsula shelf during spring, corresponding to hatching of icefish larvae from benthic nests, are transported in the southern ACC, missing South Georgia but following trajectories along the southern Scotia Ridge instead. These results suggest that the timing of release and position of early life stages in the water column substantially influence the direction and extent of connectivity. Used in complement, the two techniques promise an innovative approach for generating and testing predictions to resolve early dispersal and connectivity of populations related to the physical circulation of oceanic systems.