Combining statolith element composition and Fourier shape data allows discrimination of spatial and temporal stock structure of arrow squid (Nototodarus gouldi)

While arrow squid, Nototodarus gouldi in Australia are currently managed as a single population; biological differences in individuals between locations of capture suggests these are separate stocks requiring stock specific harvest strategies. We used two techniques to derive information about stock structure from different parts of the life cycle, providing a novel holistic approach to exploring stock structure. This study combined two techniques; statolith shape and statolith elemental composition, to determine dispersal patterns of N. gouldi between regions, and evidence of separate stocks. While adult statolith shape provided evidence that adults caught in the two locations belonged to different stocks, statolith elemental composition suggested that N. gouldi caught at each location had hatched throughout their distribution, with egg mass and juvenile drift potentially facilitated by seasonal longitudinal ocean currents. However, there was evidence of asymmetry in ontogenetic movement of N. gouldi, with adults in Victoria contributing more to the Great Australian Bight stock than vice versa; with the implication that the Victorian stock may need to be managed as the source stock.