Causes and consequences of fish size and growth changes in temperate marine coastal ecosystems

Principal supervisor

Name: Asta Audzijonyte

Email: asta.audzijonyte@utas.edu.au

Position and School: Research Fellow, IMAS

Area of expertise: Ecological modelling, ecology and evolutionary biology

Co-Supervisors

Name: Nils Krueck

Email: nils.krueck@utas.edu.au

Position and School: Research Fellow, IMAS

Area of expertise: marine ecology; fish population dynamics; fisheries management; conservation planning

Name: Rowan Trebilco

Email: rowan.trebilco@csiro.au/rowan.trebilco@utas.edu.au

Position and School: Team Leader CSIRO Oceans & Atmosphere/Adjunct Senior Researcher IMAS

Area of expertise: ecosystem modelling and assessment, systems ecology, ecosystem management

Project Description

Climate change and fishing is causing rapid changes in body sizes of many fish species. These changes are driven by multiple physiological and ecological processes, such as food availability, growth, reproduction, mortality and species redistributions. A recent study by UTAS reserachers showed that in Tasmanian rocky reefs, average body lengths for many fish species are changing by 0.5-1% per year (Figure). The associated impacts of such fish body size changes on coastal fish communities and ecosystem functioning are likely to be significant, and implications for fisheries management and conservation remain largely unexplored.

This project will build on extensive IMAS and CSIRO research expertise in fish size ecology, fisheries, coastal ecosystems function and marine conservation. It will explore drivers and consequences of body size changes in coastal Tasmanian fish species using long-term underwater visual survey data, fisehries surveys, historical records, existing and new fish growth data, and physiologically structured size-based ecosystem models for Tasmanian rocky reefs. Specifically this study will:

1. Apply Bayesian statistical models to understand changes in Tasmanian fish sizes through space and time, interactions with fishing levels, MPAs, presence of other species and multiple environmental indicators.
2. Explore reasons for body size changes through detailed analyses of growth and size structure for ecologically and economically important Tasmanian coastal species.
3. Implement size-based models developed for Tasmanian coastal ecosystems to assess impacts of body size changes (estimated in 1) and expected climate change impacts on fish communities and ecosystem dynamics. Assess performance of alternative fisheries harvest strategies/management measures to mitigate ecological and economic impacts of fish body size changes in a multi-species context.

The PhD scholarship for this project is committed by IMAS in support for Audzijonyte’s Pew Fellowship as well as a QMS top up of $5K for 3.5 years and OSHC.