MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14473

ABSTRACT: Many long-lived, deep-sea species of the higher latitudes possess protracted egg and larval phases leading to dispersal across large geographical areas. The timing of ontogenetic life-history shifts is vital for understanding dispersal potential, a key driver of spatial patterns and stock structure of Patagonian toothfish on the Patagonian Shelf. The early life-history patterns from hatching until settlement into a demersal habitat remain elusive and largely unexplored. We applied a complementary approach using otolith microstructure and trace element analysis (by LA-ICM-PS) to infer time-resolved elemental profiles that reflect the early ontogeny of age-0+ toothfish from key nursery areas on the Patagonian Shelf. Results revealed significant ontogenetic shifts across the early life-history. Key biological benchmarks were identified, including (1) the hatch date distribution (predicted mean = 3 October ± 8.47 days); (2) a period of natal dispersal (0 to 50 days post-hatch; 22 November); (3) entry of pelagic larvae onto the Patagonian shelf (50 to 100 dph; 1 January); (4) settlement into a demersal habitat (100 to 120 dph; 31 January); and (5) the start of a downslope ontogenetic migration along pathways to the continental slope (>120 dph). The results provide important considerations in terms of the complexity and protracted nature of early life-history stages in Patagonian toothfish as a complex process, informing future research objectives relating to the identification of the stock origin on the Patagonian Shelf.