Population structure of Narrow Sawfish (Anoxypristis cuspidata) across northern Australia
This report is aimed at fishery and threatened species managers, and industry. Defining management units is critical for the globally Endangered Narrow Sawfish Anoxypristis cuspidate, and genomic approaches were used to analyse the species population structure across northern Australia. Samples were obtained from bycatch of commercial fisheries in collaboration with the Northern Prawn Fishery. Barriers to gene flow were evident between all regions where there were more than three samples, demonstrating female philopatric behaviour at finer spatial scales than previously suspected. In contrast, no evidence of population structure was detected using nuclear markers, suggesting male-biased dispersal. Sampling of neonates in nursery areas would help characterise the species philopatric behaviour. Results indicate that each region should be treated as a discrete management unit, with risk of population depletion if local bycatch mortality was to exceed the species biological productivity.
Molecular analysis of newly-discovered geographic range of the threatened river shark Glyphis glyphis reveals distinct populations
This technical report is aimed at providing policy makers, fisheries managers, and conservation agencies with information on the population structure of a threatened shark of northern Australia, the Speartooth Shark. The identification of population boundaries is key to determining the appropriate spatial scale for the conservation and management of wildlife. The major river drainages (Wenlock River, Alligator Rivers, Adelaide River) comprising the species’ known range have been shown previously to be distinct genetic populations. Recent surveys have revealed a wider range than previously documented with newly-identified populations in the Daly River of the Northern Territory and the Ord River of Western Australia as well as the species’ rediscovery in Papua New Guinea (PNG). Here we aimed to test the hypothesis that the newly identified rivers (Daly and Ord Rivers), along with the Kikori River in southern PNG, also represent distinct populations given their isolation from known populations. The analysis revealed that the Ord and Kikori Rivers represent distinct populations. Results from the Daly River also suggest that this is a distinct population, although sample size was small and power limited to infer statistical significance. Each river system within the range of the Speartooth Shark should be treated as a separate management unit.
Assisting recovery of seagrass in Shark Bay, Gathaagudu - Final Report
This report outlines the findings of a collaborative project between University of Western Australia scientists and the Malgana Traditional Owners to assist recovery of seagrasses in Gathaagudu (Shark Bay) following the 2011 marine heat wave. It presents the results of field-based methods designed to assist seagrass restoration and the outcomes of these efforts for restoring ecosystem function of seagrasses. Furthermore, we provide a framework for planning future restoration activities, with step-by step examples. Suggestions are provided for the next steps in assisting people and seagrass ecosystems to heal sea country.
One panel to rule them all: DArTcap genotyping for population structure, historical demography, and kinship analyses, and its application to a threatened shark
With recent advances in sequencing technology, genomic data are changing how important conservation management decisions are made. Applications such as Close‐Kin Mark‐Recapture demand large amounts of data to estimate population size and structure, and their full potential can only be realised through ongoing improvements in genotyping strategies. Here we introduce DArTcap, a cost‐efficient method that combines DArTseq and sequence capture, and illustrate its use in a high resolution population analysis of Glyphis garricki, a rare, poorly known and threatened euryhaline shark. Clustering analyses and spatial distribution of kin pairs from four different regions across northern Australia and one in Papua New Guinea, representing its entire known range, revealed that each region hosts at least one distinct population. Further structuring is likely within Van Diemen Gulf, the region that included the most rivers sampled, suggesting additional population structuring would be found if other rivers were sampled. Coalescent analyses and spatially explicit modelling suggest that G. garricki experienced a recent range expansion during the opening of the Gulf of Carpentaria following the conclusion of the Last Glacial Maximum. The low migration rates between neighbouring populations of a species that is found only in restricted coastal and riverine habitats show the importance of managing each population separately, including careful monitoring of local and remote anthropogenic activities that may affect their environments. Overall we demonstrated how a carefully chosen SNP panel combined with DArTcap can provide highly accurate kinship inference and also support population structure and historical demography analyses, therefore maximising cost‐effectiveness.