Population structure of Narrow Sawfish Anoxypristis cuspidata across northern Australia

Delineating management units is critical for species of conservation concern such as the globally Endangered Narrow Sawfish Anoxypristis cuspidata. In this study, we used state of the art genomic approaches to analyse the population structure of A. cuspidata across northern Australia. Samples were obtained from the bycatch of commercial fisheries and subject to mitogenome sequencing as well as single nucleotide polymorphism (SNP) genotyping using the DArTseq protocol. Pairwise ΦST and haplotype mitochondrial network show evidence of barriers to gene flow between all regions for which we had more than three samples, clearly demonstrating female philopatric behaviour at even finer spatial scale than previously suspected. In contrast, no evidence of population structure was detected using over 2,000 SNP nuclear markers, suggesting male-biased dispersal. Sampling of neonates in nursery areas (before they are able to disperse) would help characterise the philopatric behaviour in this species.