This project will take an interdisciplinary approach to assess temporal and spatial differences in the diet of Antarctic fur seals to evaluate the impact of this predator on prey populations around South Georgia.
Project background
Top predators play an important role in marine environments and studies of their diet are of great value to inform ecosystem management, particularly in areas exploited by fisheries. South Georgia waters harbour commercially valuable toothfish, icefish and krill fisheries as well as 95% of the global population of the Antarctic fur seal (Arctocephalus gazella). After a period of decline due to hunting in the 18th and 19th centuries and subsequent recovery, Antarctic fur seals now numbering over 4 million individuals are assumed to increasingly compete with fisheries for the same resources. Current monitoring data indicate that some populations of Antarctic fur seals are under stress potentially due to a persistent absence of krill resources to support their diet. Therefore, integrated predator diet studies employing morphological and molecular methods are urgently needed to investigate the diet of Antarctic fur seals to devise conservation strategies for this species, as well as to determine which fisheries resources are exploited by its populations. Of paramount importance to such investigations is the assessment of spatial and temporal differences in diet composition of Antarctic fur seals, as well as differences in dietary preferences between sexes and life stages. Available monitoring data and scat sample collections at two separate locations around South Georgia, Maiviken and Bird Island, provide a unique opportunity to address this potential human-wildlife conflict and to provide important data to inform ecosystem-based management strategies that strive to sustain valuable fisheries resources while safeguarding predator populations.
Research questions
Can we improve current morphology-based identification protocols for Antarctic fur seal prey species by complementing these with genetic metabarcoding?
Does Antarctic fur seal diet differ between the two South Georgia locations, Maiviken and Bird Island, between seasons and between years?
Does diet reflect niche partitioning between sexes of Antarctic fur seal?
Is the increasing Antarctic fur seal population having a detrimental impact on demersal fish populations?
Can we improve quantification of krill biomass from dietary DNA-based data from Antarctic fur seal populations?
How can diet studies of Antarctic fur seals inform ecosystem-based management of South Georgia fisheries?
Methodology
This project will adopt an interdisciplinary approach using contemporary morphological identification methods of prey items with DNA metabarcoding. Representative samples of prey species from archived biological collections will be sequenced as required to create a reference database for prey identification in Antarctic fur seal scats. In addition, further sequencing will be conducted to resolve taxonomic uncertainty associated with larval and juvenile stages of prey items to inform current protocols based on morphological identification. Ongoing collection of scats as part of Antarctic fur seal monitoring in the two study areas will be used for morphological identifications of remaining prey hard parts as well as for genomic DNA extractions. Quantitative estimates of demersal prey species will be generated from a time series of benthic fish surveys, using established biomass estimate methods. In addition, otoliths recovered from scats will be used to estimate the size/age of fish predated by Antarctic fur seals, using established biometric relationships and otolith ageing techniques. Genetic analyses to identify prey species from Antarctic fur seals will follow standard DNA metabarcoding and taxon-targeted protocols currently used for marine mammal diet studies. A novel approach will be implemented to identify krill haplotypes from Antarctic fur seal diet data to improve estimates of krill biomass in the study areas. Subsequent bioinformatic pipelines implemented in Geneious, Python and R software packages will be used for qualitative and semi-quantitative analyses of the prey sequences. Results from the morphological and molecular genetics methods will be compared to refine current prey identification protocols. Diet composition will be compared between the two study areas, across different sampling periods (season and years), and between sexes.
Year 1. Molecular genetics training. Morphological identification of prey items training (using King Edward Point protocols). Construction of reference database for genetic identification of Antarctic fur seal prey species using archived biological collections. Application of the reference database to improve morphological taxonomic identification of larval and juvenile prey items.
Year 2. DNA metabarcoding and taxon-targeted bioinformatics training. Genetic analyses of diet composition, including identification of krill haplotypes. Morphological analyses of hard prey items. Reconstruction of fish biometrics from otolith dimensions, along with training in sclerochronological analysis of otoliths.
Year 3. Genetic sexing of Antarctic fur seal scat samples. Statistical analyses training. Spatial, temporal and sex-dependent data analyses. Training and application of swept area biomass estimation techniques for demersal fish species.
In addition to the expertise provided by the supervisory team, we also count with the collaboration and ad-hoc project support of Dr Jaume Forcada (British Antarctic Survey) and Dr Mark Belchier, Director of Fisheries and Environment, Government of South Georgia and South Sandwich Islands.
Training
A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. Specialised skills will include morphological and genetic analyses for species identification, molecular genetics, genomics, bioinformatics, and applied statistics. In addition to these bioscience skills, the candidate will acquire a suite of other transferable skills including data management, effective communication with stakeholders, and the application of scientific evidence to inform Antarctic fur seal populations and fisheries management. In addition to the expertise provided by the supervisory team, we also count with the collaboration and ad-hoc project support of Dr Jaume Forcada (British Antarctic Survey) and Dr Mark Belchier, Director of Fisheries and Environment, Government of South Georgia and South Sandwich Islands.
Requirements
The successful candidate will have an interest in ecosystem management and marine biology, a degree in a related biological subject, experience in molecular biology, and excellent communication skills to interact with different project partners and stakeholders. Relevant experience in gut/faeces content analyses and knowledge of DNA metabarcoding will be advantageous.
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