Otolith chemistry reveals local population structure of Antarctic toothfish (Dissostichus mawsoni) within the CCAMLR Subarea 48.6

Antarctic toothfish Dissostichus mawsoni is an important fish species with ecological and economical value and that distributed in the high latitude of the Southern Ocean. The CCAMLR subarea 48.6 is one of an important fishing zone, however, the local population structure of D. mawsoni is unknown in this regions, which hampered the understanding on population dynamics of this species and the management of toothfish fishery. The chemistry in the otolith can often be used to distinguish population structure of fish. In order to understand the local population structure of D. mawsoni in different research blocks (48.6_-2, 48.6_-3 and 48.6_-4) of CCAMLR subarea 48.6. Otolith samples of D. mawsoni (n=32) were collected from those blocks. The elements in the nuclei and edges of otolith were sampled using Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Using Sr, Mg, Ba and Ca, the differences in Sr·Ca^-1, Mg·Ca^-1 and Ba·Ca^-1 for the otolith of D. mawsoni were examined between three blocks. The results indicated that no significant difference in Me·Ca^-1 of either otolith nuclei or edges between three blocks. No significant difference in nucleus chemistry showed that the specimens that captured from 3 different blocks may source from the same spawning/nursery ground. No significant different of edge chemistry demonstrated that the habitat of D. mawsoni was consistent between three blocks. Significant differences between nucleus and edge chemistry indicated that habitat of D. mawsoni may change with ontogeny and different between spawning/hatching ground and the area that fish captured. Otolith chemistry with combining to oceanography and tagging data may provide more accurate information on predicting biophysical interaction and locating nursery ground of D. mawsoni in and above CCAMLR subarea 48.6.