Degree type
PhD
Closing date
1 June 2025
Campus
Hobart
Citizenship requirement
Domestic
About the research project
Over the last century humans have drastically changed the size structure and reduced the size diversity of fish populations. Many commercially fished species are known to have strongly truncated size structure, and similar effects are likely for many recreationally fished species, although they are rarely explicitly documented. Nevertheless, as the human impacts on fish size structure are becoming more recognised, various management interventions have been proposed and implemented to improve it, both in Australia and globally. These management measures include the use of fisheries size limits (minimum, maximum or harvest slot limits), spatial protection, community managed areas, catch and release recreational fishing, and, although not directly targeted at size structure, habitat restoration and artificial habitats. Yet, the effectiveness of these measures on fish population size structure often remains unclear, mostly because systematic and targeted data collections are rare and because other environmental factors, such as global heating, are also impacting on fish sizes. This project aims to address this knowledge gap through analysis of large datasets collected through underwater visual and camera-based surveys (Reef Life Survey and other visual survey datasets, BRUVs and other camera based surveys), scientific surveys and citizen science data from recreational fishing. The datasets will be obtained via the existing international collaborative networks from the supervisory team (from Australia, Indonesia, Europe, USA, Canada and elsewhere). Broadly, the project aims to assess effectiveness of specific management measures and provide recommendations for their further improvement. More specifically the project has three broad goals and the student will work on some or all three of the below listed areas:
1) Analyse changes in fish size structure inside and outside spatial protection areas, to assess how effectively different levels of spatial protection can restore fish size diversity and whether these effects are likely to extend outside the protected areas. Specifically, in this chapter the student will explore underwater census datasets in Australia and globally to assess for long term trends in a species-level size structure across hundreds of fish species. We will use Bayesian mixed effect models, possibly with informative priors, to account for random effects due to location, environmental impacts, sampling selectivity and species. Changes in size structure will be statistically compared to the expected unfished species size distributions (based on the results from the current work in the ARC DP project, led by Audzijonyte and Krueck) and contrasts within and outside the protected areas will be used to account for environmental impacts. This part of the project does not aim to understand or disentangling the processes affecting size structure (growth, mortality, recruitment), but only the overall effects. The quantitative nature of this part of the work is in managing large fish body size datasets and developing and applying proper Bayesian statistical techniques to account for random and non random fish body size variation due to factors other than spatial protection.
2) This chapter will address the question about the effectiveness of harvest slot limits in improving recreational fish species size structure. Harvest slots (minimum-maximum size limits) have been introduced in many coastal and freshwater areas, but there is a great lack of systematic analysis on their effects, and in most cases attribution of harvest slots on changes in size structure remains difficult. While there are many modelling studies demonstrating the effectiveness of harvest slot limits and expected effects on size structure, empirical tests remain virtually non-existent due to insufficient data to address multiple factors for a specific location. We will aim to address this knowledge gap by compiling a range of scientific survey and underwater census datasets from locations in Australia, USA and Europe, collected in sites with and without harvest slot limits and in this way increasing the analysis power. These datasets will be analysed in a Bayesian framework to assess whether locations with harvest slot limits have better size structure (defined through several commonly used population size metrics), while accounting for multiple random effects of environmental impacts, sampling, human density, location and likely compliance, and duration of harvest slot regulations. Datasets will be obtained through the collaborative networks of the supervisory team, leading to a large multi-author publication.
3) Habitat restoration and augmentation measures have been attempted across multiple locations around the globe and there is currently large kelp and seagrass restoration projects conducted in Tasmania and Australia. In most cases effectiveness of habitat restoration measures is assessed through changes in fish species composition and biomass, but changes in size structure at a species and community level are also important. This part of the project will explore how kelp and seagrass restoration in Australia changes species and community level size structure in fishes. The study will use existing underwater survey datasets and may also include new targeted surveys, collected in collaboration with the kelp restoration team. As in the previous sections, we will apply statistical Bayesian methods to assess changes in fish population and community size composition due to habitat restoration, while accounting for other climate and human harvesting related processes. The project will also apply size based multi-species models (based on the Tasmanian rocky reef model, in Audzijonyte et al. 2023 Plos Biology), modifying the model to include seagrass and kelp impacts on fish recruitment and growth.
Primary Supervisor
Funding
Applicants will be considered for a Research Training Program (RTP) scholarship or Tasmania Graduate Research Scholarship (TGRS) which, if successful, provides:
- a living allowance stipend of $33,511 per annum (2025 rate, indexed annually) for 3.5 years
- a relocation allowance of up to $2,000
- a tuition fees offset covering the cost of tuition fees for up to four years (domestic applicants only)
If successful, international applicants will receive a University of Tasmania Fees Offset for up to four years.
As part of the application process you may indicate if you do not wish to be considered for scholarship funding.
Additional funding
- If successful, applicants will also receive a top-up scholarship of $6,000 per annum for 3.5 years. This scholarship is funded by the Quantitative Marine Science (QMS) Program
- If successful, international applicants will receive single Overseas Health Cover (OSHC), funded by the Quantitative Marine Science (QMS) Program.
Other funding opportunities and fees
For further information regarding other scholarships on offer, and the various fees of undertaking a research degree, please visit Scholarships and fees.
Eligibility
Applicants should review the Higher Degree by Research minimum entry requirements.
Ensure your eligibility for the scholarship round by referring to our Key Dates.
Additional eligibility criteria specific to this project/scholarship:
- Applicants must be able to undertake the project on-campus
Selection Criteria
The project is competitively assessed and awarded. Selection is based on academic merit and suitability to the project as determined by the College.
Additional essential selection criteria specific to this project:
- Demonstrated skills or strong interest in quantitative data analysis
- Strong quantitative and statistical skills and Bayesian methods
- Strong experience in using quantitative methods in R
- Ambition to work with large datasets
- Demonstrated proficiency in written and verbal English language
Application process
- Select your project, and check that you meet the eligibility and selection criteria, including citizenship;
- Contact Dr Asta Audzijonyte to discuss your suitability and the project's requirements; and
- In your application:
- Copy and paste the title of the project from this advertisement into your application. If you don’t correctly do this your application may be rejected.
- Submit a signed supervisory support form, a CV including contact details of 2 referees and your project research proposal.
- Apply prior to 1 June 2025.
Full details of the application process can be found under the 'How to apply' section at Research degrees.
Following the closing date applications will be assessed within the College. Applicants should expect to receive notification of the outcome by email by the advertised outcome date.
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