Restoration of fish populations in semi-arid ecosystems
Date
2017
Authors
Lyon, Jarod Paul
Editors
Advisors
Gillanders, Bronwyn
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Theses
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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.
School/Discipline
School of Biological Sciences
Dissertation Note
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Biological Sciences, 2018
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