Fish Population Biology
Length and age compositions, growth and reproductive biology
• Major recreational and commercial fish species and other abundant fish species.
• Main focus is on species in estuaries and marine waters of south-western Australia.
• Detailed studies have also been conducted, however, on recreational and commercial fish species and fish communities along the entire Western Australian coast.
• Attention will be increasingly paid to determining the relationships between the estuarine and marine assemblages of marine-estuarine opportunistic species. Genetics will form a crucial component of these studies.
• Particular attention is been paid to collaborating closely with Norm Hall to refine, where applicable, the methods for analysing the above variables and thus provide the basis for making rigorous statistical comparisons at various spatial and temporal scales and between sexes of gonorchoristic and hermaphroditic species.
• The data obtained for certain species at different latitudes are subjected to analyses aimed at testing particular theories, such as the Metabolic Theory of Ecology.
• Sclerochronological studies, using the growth increments in otoliths, are being used to determine the extent to which the growth of certain medium to long-lived fish are related to inter-annual differences in environmental variables, such as water temperature. The results of these studies are relevant to discussions of the potential effects of climate change.
• Larval studies are focusing on elucidating the environmental variables that influence the distribution and recruitment success of Black Bream. The data acquired during these studies is being used to gain further information on the early stages in the life cycle of other fish species.
• Restocking will increasingly be seen as a means of replenishing stocks that have been depleted and/or anthropogenic effects. The unique and ongoing study on Black Bream in the Blackwood River Estuary will provide a benchmark for restocking studies in Western Australia. Further studies, some involving collaboration with the Australian Centre for Applied Aquaculture Research at the Challenger Institute of Technology, are being aimed at developing a better understanding of the biology and ecology of the Western School Prawn in the Swan River Estuary and the efficacy of using restocking to replenish the stocks of this species.
• The above restocking projects are accompanied by robust genetics studies to ensure that any restocking is conducted in a responsible manner.
• Dietary studies have concentrated on determining, in conjunction with Margaret Platell and research students, the extents and ways in which the diet of individual species changes with body size and season and sometimes region. During recent years, Bob Clarke has been involved in several of these studies and been responsible for developing a combination of an appropriate suite of statistical analyses to tease out the main factors influencing dietary composition.
• Food webs. A readily comprehensible food web, that provides an understanding of ecosystem function, has been constructed for the main demersal fish species on the lower west coast of Australia using an innovative approach developed by Bob Clarke to analyse the dietary data acquired for these species over many years. At present, data are being accumulated for fish species on the south coast to facilitate the construction of a similar web.
Modelling and stock assessment
Research on modelling, stock assessment and social and economic evaluation work on recreational fishing pressure and human behavioural response to management is being undertaken in the marine and estuarine environment. This research has relevance for the management of commercial and recreational fisheries and the conservation of fish stocks and protection of biodiversity.