Antarctic Toothfish Dissostichus mawsoni in the South Orkney Islands: Using Stable Isotopes and Otoliths to Test Current Hypotheses About Nursery Areas and Demographic Units

We used otolith chemistry tools to test and complement current hypotheses about habitat use and connectivity between Dissostichus mawsoni sub-populations in CCAMLR area 48. Sagittal otoliths from 45 fish sampled around the South Orkney Islands were analysed. Their elemental (Li, Na, Mg, Cr, Mn, Sr, Sn, and Ba, relative to Ca) and isotopic (δ18O and δ13C) signatures were examined in both nuclear and marginal regions, representing juvenile and adult stages, respectively. Potential nursery habitats were geo-located by comparing observed and expected δ18O values. Chemical differences between nuclear and marginal regions were indicative of ontogenetic displacements to deeper offshore habitats, suggesting a discrete habitat shift between 11 and 13 years-old. Data supported the existence of two nursery origins contributing to the study area population. Nonetheless, the location of these origins was unclear and didn not provide any direct support to the hypotheses being currently considered by CCAMLR. Thus, the location and connectivity between nursery and adult habitats, as well as their spawning site fidelity, need to be assessed before disregarding alternative hypotheses07160260Citation: To be added by editorial staff during production. Academic Editor: Firstname Lastname Received: date Revised: date Accepted: date Published: date Copyright: © 2024 by the authors. Submitted for possible open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Citation: To be added by editorial staff during production. Academic Editor: Firstname Lastname Received: date Revised: date Accepted: date Published: date Copyright: © 2024 by the authors. Submitted for possible open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)..