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Type: Theses
Title: Restoration of fish populations in semi-arid ecosystems
Author: Lyon, Jarod Paul
Issue Date: 2017
School/Discipline: School of Biological Sciences
Abstract: An abundance of ecological theory highlights the importance of taking temporal and spatial scale into account when managing fish populations. However, in heavily modified riverine systems that can cross many social, economic and political boundaries, the links between scientific results and the day-to- day realities of managing for fishery and biodiversity outcomes, can be difficult. Australia is the world’s driest continent, and in our largest and most productive water catchment (Murray-Darling Basin), many different interventions are occurring in an attempt to strike a balance in a system where both agricultural and environmental outcomes are prioritised. While measuring agricultural outputs is relatively easy, it is much more difficult to quantify the outcomes of river restoration on fish species that have life-history processes spanning huge spatial and temporal scales. In this thesis, I present case studies providing both lines of evidence on the success of restoration programs, and additionally outline linkages with theory that frames this evidence of success within a conceptual framework built on restoration theory. In Chapter 1, I outline why linking ecological concepts to management objectives is important, as it provides managers with an understanding of ‘how’ their intervention will lead to a tangible outcome, and this is significant in riverine systems where pressures on restoration resources are large. Next, I quantify connectivity (measured as rates and timing of fish movements) between floodplain and main-channel habitats, and describe how these are affected by differing connection regimes (Chapter 2). With altered flow regimes common in most large waterways in the Murray-Darling Basin, data linking rates of fish movement to hydrological change are useful when setting water-delivery schedules. Using a case study from the Ovens River, I show that re-introduction of fish is a valid conservation action (Chapter 3). My results show that the survival of stocked cohorts is highly variable, so that ensuring a re-introduction program that is sufficient in spatial and temporal scale to overcome a range of environmental conditions (such as changes to water quality and quantity) is necessary to be successful. I also provide the first published data of histology of the endangered trout cod (Maccullochella macquariensis) from a natural riverine system, necessary information for those charged with conserving this species. Demonstrating positive outcomes from restoration is necessary for investors of waterway restoration means that data reliability is essential. In Chapter 4, I describe a field-based study of electrofishing efficiency, where I test the influence of turbidity, depth and species identity on detection rates of target species. Increasing depth, turbidity, and changes in species and size of fish, all influenced electrofishing detection probability at my study site. The major implication here is that if one does not account for imperfect detection, sampling can either fail to identify successful restoration, or over-estimate its change to the system. Using a range of data sources, and measuring population processes rather than just abundances, are ways to overcome variable efficiency over time. I measured the response of native fish species to a habitat-restoration trial by collecting data on immigration, emigration, and survival to determine how fish populations responded following a habitat restoration program in the Murray River (Chapter 5). I found that populations of the target species (Maccullochella peelii) and golden perch (Macquaria ambigua) increased following restoration, while staying stable in reference reaches, and that this increase was primarily driven by immigration from a nearby source population. In my general discussion, I provide several recommendations for managers and researchers that I have shown will increase the probability of successful river restoration (Chapter 6). In particular, by linking our knowledge of the scale of the life-history processes, in particular movement and migration, of target fish species, and investing specifically at these scales, the probability of successful restoration increases.
Advisor: Gillanders, Bronwyn
Dissertation Note: Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Biological Sciences, 2018
Keywords: Research by publication
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
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