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Type: Thesis
Title: [EMBARGOED] Linking Chemistry and Sclerochronology to Physiological Processes in Fish
Author: Martino, Jasmin Carmel Amina
Issue Date: 2019
School/Discipline: School of Biological Sciences
Abstract: Physiology underpins how species survive, reproduce and interact with their environment. Many fish populations are difficult to directly monitor due to the vastness and complexity of aquatic habitats. Retrospective tracking using intrinsic biomarkers is a powerful alternative that is both effective and inexpensive. This thesis investigates physical and chemical biomarkers for reconstructing physiological processes (growth and metabolic rate) in fish. Physiological histories can uncover health and physical performance of individuals, reveal biological responses to external environments and are key in understanding the functioning, movement and biomass of wild fish populations. My study species was the iconic and valuable fishery species, Australasian snapper (Chrysophrys auratus). Recent changes and downturns in commercial catch of snapper have provoked concerns about long-term sustainability and spatial structure of the fishery in South Australia. Exposing physiological mechanisms behind the population and fishery dynamics will assist to understand contributing factors to the changes. Somatic growth rate is a primary predictor for a wide-range of biological and ecological processes. Using otolith sclerochronology and mixed-effects modelling, I reconstructed nearly four decades (37 years) of growth in snapper across four oceanographically diverse regions and investigated the influence of extrinsic factors. Growth was found to decline in the two most productive regions. Across all regions, snapper growth was influenced by primary productivity, temperature, extreme climatic episodes, and population density. In experiemental settings, I investigated the link between stable isotopes in fish tissues and physiology. Juvenile snapper were reared in four temperature treatments and carbon isotopes (δ13C) were measured in hard-tissues (otoliths), soft-tissues (muscle and liver) and potential carbon sources (water and diet). Intermittent-flow respirometry was then used to calculate metabolic rates. Metabolic effects significantly influenced the incorporation of carbon isotopes in all tissues. A significant negative linear relationship was found between carbon isotopes and metabolic rates. However, with increasing stress (heat and exertion), this negative relationship switched to an increasingly positive relationship. This research validates the use of carbon isotopes as metabolic biomarkers and is an important precursor to using otolith chemistry to track metabolic rates in the field. The relationships between otolith chemistry, intrinsic properties, and environmental conditions were then investigated in wild snapper. I analysed lifetime profiles of stable isotopes of carbon and oxygen (δ18O), and elemental signatures of magnesium (Mg:Ca), strontium (Sr:Ca), barium (Ba:Ca), manganese (Mn:Ca) and lithium (Li:Ca) in snapper across two oceanographically diverse regions (northern Spencer Gulf and the South-East in South Australia) and three cohorts (1979, 1991, 2006) to examine regional and temporal variation. Mixed-effects modelling was used to investigate the influence of intrinsic properties (age, otolith growth, fish length, sex) and environmental factors (sea surface temperature and chlorophyll-a) on chemical markers. Carbon isotopes, magnesium and, to a lesser extent, strontium were found to relate to intrinsic characteristics and their utility in reconstructing lifetime physiological trends is suggested. The chemical chronologies also improved our understanding of movement histories in wild snapper populations. Our results highlight the use of isotopic and elemental chemistry in otoliths for reconstructing environmental, migration and physiological histories in wild fish populations. In this thesis, I demonstrate the potential of physical and chemical tags in otoliths as physiological biomarkers. The developed techniques are transferable to other fish species to address a widerange of ecological questions. The long-term growth, chemical and metabolic histories developed for snapper help to understand the processes driving population dynamics and productivity. Intrinsic biomarkers are powerful tools and will help sustainable management of wild fish into the future.
Advisor: Gillanders, Bronwyn
Doubleday, Zoe
Fowler, Anthony
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2019
Keywords: Fish biology
fisheries science
otolith science
Provenance: This thesis is currently under Embargo and not available.
Appears in Collections:Research Theses

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