Matthew Cameron

Relationships between fish populations and the physical structure of rocky reefs, including interaction with fishing pressure inside and outside marine protected areas

Supervisors: Dr. Craig Johnson (UTAS), Dr. Neville Barrett (TAFI), Dr. Graham Edgar (TAFI), Dr. Peter Last (CSIRO)

Scientific background:

Partly as a consequence of declining inshore biodiversity and perceived deficiencies in traditional single-species approaches to fisheries management, a growing number of “no-take” marine protected areas (MPAs) are being proclaimed worldwide. In tandem with this legislative activity, scientific research on MPAs represents a rapidly growing field. The declaration of MPAs represents a manipulative experiment at a vast, and ecologically meaningful spatial scale.

An ARC-funded study that compares biological changes in newly declared MPAs with changes in reference sites is presently underway, involving collaboration between the University of Tasmania, CSIRO, NSW Marine Park Authority, WA Department of Conservation and Land Management, SA Department of Environment and Heritage, Tasmanian Department of Primary Industries, Water and Environment, and Tasmanian Parks and Wildlife Service. This continental-scale study, extending from NSW to WA and around Tasmania, includes the monitoring of fish, invertebrate and plant communities in MPAs and adjacent reference sites for several years from prior to declaration of the MPAs.

Project outline and objectives:

The proposed PhD project will be closely aligned to the ongoing ARC investigation, with logistic costs covered by that project. It will utilise a subset of ARC field sites with long-term data. Thus, results of mensurative and manipulative experiments can be referenced against a large multi-year data set that includes density information on local reef fish and invertebrate predators and grazers, and percentage cover of plants and sessile animals.

The main focus of the project will be an investigation of how fish assemblages inside and outside MPAs are influenced by the physical complexity of reef habitat. The project will link closely with a second PhD study (recently commenced) on relationships between invertebrate assemblages and the physical complexity of reefs. The sum of these two studies, together with the long-term data obtained in the ARC investigation, should be much greater than the sum of the parts, because aspects of reef structure that mediate trophic interactions between fishes and invertebrates can be distinguished. 
                                              
Theoretical benefits from the project will arise through the production of conceptual and mathematical models that indicate how fish populations are constrained by interactions between the heterogeneity of reef habitat, diet, and fishing pressure. The study of mechanisms that constrain the ‘fit’ of mobile marine animals into physical habitat space is an area of research that has been almost completely neglected to date.
                                                                                     
Outcomes of practical relevance from the project will include the creation of models that describe how habitat structure affects recovery of fish species within MPAs following cessation of fishing. MPA locations presumably vary greatly in habitat quality for particular species due to variation in reef structure, with complex habitats likely to generally experience fastest and more intense responses to release from fishing pressure. Quantifying various aspects of substratum complexity such as fractal dimensions and relating these data to patterns of fish density will enable us to better understand biotic responses following the establishment of MPAs, and assist in site selection for future MPAs.