Predicting hydraulic structure-induced barotrauma in Australian fish species

Abstract

When fish pass downstream through river infrastructure, such as dams and weirs, barotrauma may occur as a result of rapid decompression. In severe cases, barotrauma may lead to mortality. Different species are likely to respond differently to these decompressions. Therefore, to predict barotrauma for a specific species, surrogate species may not be a valid approach, and it may be necessary to examine each species individually. For the present study, Australian bass and carp gudgeon were exposed to a range of rapid decompressions using hyper- and hypobaric hydro-chambers and examined for injuries and mortality. Rapid decompression data from these two fish species, in addition to previously examined Murray cod and silver perch, were evaluated to determine which injuries were highly associated with and likely to predict mortality. Dose–response logistic regression models were developed for each species to predict injury and mortality over a range of rapid decompressions. These models are valuable for estimating injury and mortality rates for fish passing though river infrastructure and can be applied to specific sites where pressure profiles have been developed. Applying these models to current and future infrastructure can provide important insight into what measures or design alterations may be necessary to reduce negative effects of infrastructure on fish populations.

The Susceptibility of Juvenile American Shad to Rapid Decompression and Fluid Shear Exposure Associated with Simulated Hydroturbine Passage

“…Fish were considered injured if they were injured in any way or died due to exposure to rapid decompression. A statistical analysis was conducted to classify specific injuries as mortal injuries [31,34,41]. Mortal injuries included injuries that were highly associated with mortality (Odds ratio >1 and Fisher's exact test p < 0.05; SigmaPlot v13.0) and, if highly associated, were a significant predictor of mortality (stepwise regression model p < 0.05; SigmaPlot v13.0).…”

“…Juvenile American shad tested in this study are also more susceptible to effects of shear and rapid decompression than other fish species, such as silver and yellow phase American eel (Anguilla rostrata), juvenile lamprey (Lampetra spp. ), juvenile rainbow trout (Oncorhynchus mykiss), and a few Australian species, which have been examined similarly [24,30,34,36]. This suggests that measures (i.e., turbine designs or operational modifications) taken to protect juvenile salmonids, or other fish species at hydropower facilities may not be sufficient to protect juvenile American shad.…”

“…In general, exposure included pressure increases to about 400 kPa over a period of about 20 s to simulate travel through the turbine intake before a rapid decrease (<0.5 s) to simulate the fish passing the turbine runner. Pressure was then quickly (≈2-5 s) returned to near surface pressure (101.3 kPa) to simulate the fish exiting the facility and entering the downstream channel [34,39]. The chambers were programed so that fish were exposed to a range of rapid decompression, with a targeted nadir pressure (lowest pressure) range of 10-140 kPa.…”

“…These pressures have been observed to range considerably, from <10 kPa absolute to well above atmospheric pressure [29,32]. The sudden decrease in pressure may lead to a variety of barotraumas to the fish, including swim bladder rupture, exophthalmia, and emboli or emphysema throughout the organs and tissues of the fish [31,33,34]. Barotrauma injuries can result from gasses expanding within the body (explained by Boyle's Law) or bubble formation in the blood and tissues when gas comes out of solution (explained by Henry's Law) and can vary depending on the operating conditions of the hydropower facility and the species of fish [31,33,35].…”

American eel state of buoyancy and barotrauma susceptibility associated with hydroturbine passage

“…The degree to which a fish is exposed, to rapid decompression, can vary dramatically (Duncan, 2011(Duncan, , 2013Duncan and Carlson, 2011;Fu et al, 2016;Hou et al, 2018), but when severe, barotrauma (physical damage to body tissues caused by changes is pressures) can occur, which can potentially be fatal. Initially, the focus of hydraulic structure induced barotrauma has focused on salmonid species passing through large hydroelectric turbines (Brown et al, 2012a;Pflugrath et al, 2012); however, to further improve fish passage, additional species and structures are continuously being examined (Colotelo et al, 2012;Brown et al, 2013;Boys et al, 2016;Fu et al, 2016;Pflugrath et al, 2018;Boys et al, 2018;Beirão et al, 2018;Silva et al, 2018). As additional species are examined, it is clear that the methodology of assessing barotrauma, that is suitable for one group of species may not be suitable for other species, particularly the state of buoyancy prior to decompression.…”