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 strong heterogeneity between the Antarctic Peninsula and South Georgia consistent with a population boundary, and evidence of finer-scale heterogeneity between sampling areas on the Antarctic Peninsula. At South Georgia, the nucleus chemistry was similar between the eastern and northern shelves, indicating a single, self-recruiting population. Consistent with the otolith chemistry, simulations of the large-scale circulation predicted that particles released at 100-300m depth 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 south Scotia Ridge instead. These results suggest 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 to generate and test predictions, and resolve early dispersal and connectivity of populations related to the physical circulation of oceanic systems.