Population structure and genetic diversity of the Critically Endangered bowmouth guitarfish ( Rhina ancylostomus ) in the Northwest Indian Ocean

The bowmouth guitarfish ( Rhina ancylostomus ) is a unique and relatively understudied species of wedgefish with a distribution spanning the Indo-Pacific Oceans. Due to targeted and bycatch fisheries, this species is experiencing serious declines across its range. It is now considered among the most threatened species of elasmobranch. Despite this, species-specific management is limited, particularly around primary fishing hotspots. This is in part due to knowing very little about fundamental population processes. Here, we combine mitochondrial and single nucleotide polymorphism (SNP) data to carry out the first genetic assessment of R. ancylostomus across the Northwest Indian Ocean. We find evidence for population structure across the species’ northwest range that is best explained by dispersal constraints and therefore emphasises the importance of habitat connectivity. We also uncover a cline in genetic variation from east to west of the sampling distribution and identify regions in potential need of heightened protection. In doing so, our study provides baseline information to support conservation management of R. ancylostomus and highlights the value of genomic data in elasmobranch conservation.