Integrated Genetic and Statolith Shape Analysis Reveals the Population Structure of<em> Todarodes pacificus</em> in the Coastal Waters of China

Understanding stock structure is a priority for evaluating population dynamics of commercially fished cephalopods under fishing pressure and environmental changes. This study employed a multidisciplinary approach to clarify the stock structure of Todarodes pacificus, a highly migratory squid species exploited by Asia-Pacific countries. Based on the analysis of statolith increments, summer and autumn cohorts were identified. Low haplotype diversity was revealed by two mitochondrial DNA markers (COI, 16S) and one nuclear DNA (nuDNA) marker (ODH). There was no significant genetic differentiation through phylogenetic trees and haplotype networks. The overall shapes between cohorts were significantly different, along with high classification success, could be used as a classification marker. This result offers new insights into the influence of genetic and environmental factors on statolith shape. The integrated results provide a comprehensive understanding of the stock structure of T. pacificus, laying the foundation for resource development and the conservation of the species.