Quantifying stressors and predicting injury and mortality in fish passing downstream through weirs and turbines

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Copyright: Pflugrath, Brett
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Abstract
Dams and weirs have altered river conditions and contributed to declines in freshwater fish populations. One factor responsible for this is exposure to extreme hydraulic conditions as they pass downstream. These conditions create stressors including mechanical strike, shear forces, and rapid decompression. Currently, focus has been on reducing stressors at large hydropower facilities, but there is an increasing need to expand this focus to low head hydropower and weirs. This research investigated hydraulic stressors fish encounter when migrating downstream past low head dams and weirs, further examined how operations of a sluice gate may improve fish welfare, developed decompression dose-response relationships for a selection of fish species, and predicted rates of injury/mortality for four species of fish at four dams/weirs. Autonomous sensors were deployed to quantify hydraulic stressors at a selection of low head dams and weirs where strike, shear, and rapid decompression were recorded. A sluice gate was constructed and installed into a 90 cm laboratory flume and examined using sensors under various gate openings and flow rates, which determined that increasing the gate opening can reduce the occurrence and magnitude of strike. Fish were exposed in the laboratory to rapid decompression to develop predictive models for injury and mortality in four fish species. Decompression testing also revealed that swimming activity alters barotrauma susceptibility in fish. Additionally, Sensor Fish and decompression results were then used to model fish injury and mortality when passing the dams and weirs. The model suggested that injury could occur in as many as 96% and mortality in as many as 60% of passing fish. However, injury and mortality varied between structures and species. This research advances our understanding of how low head dams and weirs affect downstream migrating fish and provides recommendations for design and operation of low head facilities. It was concluded that sluice gates should be designed with a submerged sloping apron and operated at the greatest opening possible; plunge pools need to be sufficiently deep for sharp crested gates; and barotrauma may be reduced in fish passing turbines by adjusting the intake to take water from the surface.
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Author(s)
Pflugrath, Brett
Supervisor(s)
Cathers, Bruce
Peirson, William
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Publication Year
2017
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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download public version.pdf 7.03 MB Adobe Portable Document Format
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