Variation in stable isotope (δ18O and δ13C) signatures in the sagittal otolith carbonate of king threadfin, Polydactylus macrochir across northern Australia reveals multifaceted stock structure

►There were significant differences in stable isotope signatures among populations. ►This spatial separation indicates P. macrochir have a complex stock structure. ►Stocks seem to be associated with large coastal embayments on fine spatial scales. ►There is potential for localised depletion of stocks on small spatial scales. ►Widely distributed fish species can show strong localised population structure.