In order to provide recommendations on how to manage flow releases to mitigate their effects on aquatic communities, my thesis aims to understand how past hydraulic variations influence the abundance of fish and macroinvertebrates at two spatial and biological scales:
1/ The reach scale (a few hundred meters of river length; community scale)
2/ The microhabitat scale (a few square meters; individual scale).

Hydropeaking is the frequent and rapid artificial variations in flow to meet sub-daily peaks in electricity demand. The hydraulic variations it generates can cause the stranding or forced drift of organisms, which can lead to changes in aquatic community structure. To date, at either the reach (100 m) or microhabitat (~ m2) scale, few studies have demonstrated transferable links between hydropeaking variables (e.g. upramping rate of current velocity) and biological responses (e.g. species density, habitat selection). It is often difficult (1) to translate flow into proximal hydraulic conditions and (2) to test the relative influence of hydropeaking versus other environmental drivers. To address this knowledge gap, in our first paper, we evaluated the effects of hydraulic variations from hydropeaking on fish communities. In particular, we conducted an original combination of spatial (over 45 river reaches including six groups of nearby reaches) and temporal (over 3 to 17 years) analyses. We found that the influence of hydropeaking was secondary compared to well-known spatial variations in fish assemblage structure along longitudinal gradients, and negative influences of floods on annual densities. However, spatial and temporal analyses suggested that hydropeaking may disfavour fish species from medium-sized rivers compared to species from small rivers (trout, minnow and sculpin). To better understand the effects of hydropeaking, in our second paper, we investigated habitat selection by fish and macroinvertebrates in a medium-sized river (Ain River) at the microhabitat scale (~ m2). To do so, we used observations of fish abundances in 1180 microhabitats (507 sampled by electrofishing, 673 by snorkeling) and macroinvertebrates abundances in 36 microhabitats (hyporheic and benthic) as well as a 2D hydraulic model to estimate the past hydraulics of microhabitats (for the 15 days before sampling). Overall, past hydraulics influenced microhabitat selection, with a stronger effect on macroinvertebrates than fish and a stronger direct influence of dewatering (3-15 times fewer macroinvertebrates in microhabitats that were dewatered) than high velocities. Fish follow their suitable habitat conditions and thus avoid high velocities while macroinvertebrates stay and hide. Based on these two analyses, operational perspectives are proposed, in particular to integrate the results into management models.

References

• Capra H, Plichard L, Bergé J, Pella H, Ovidio M, Mcneil E, Lamouroux N. 2017. “Fish Habitat Selection in a Large Hydropeaking River: Strong Individual and Temporal Variations Revealed by Telemetry.” Science of the Total Environment 578: 109-120.
• Bain MB, Finn JT, Booke HE. 1988. “Streamflow Regulation and Fish Community Structure.” Ecology 69(2): 382–92.
• Freeman MC, Bowen ZH, Bovee KD, Irwin ER. 2011. “Flow and Habitat Effects on Juvenile Fish Abundance in Natural and Altered Flow Regimes.” Ecological Applications 11 (1):179–90.
• Lamouroux N, Capra H, Pouilly M, Souchon Y. 1999. “Fish habitat preferences in large streams of southern France“. Freshwater Biology 42(4):673-687.
• Mérigoux S, Lamouroux N, Olivier JM, Dolédec S. 2009. “Invertebrate hydraulic preferences and
• predicted impacts of changes in discharge in a large river”. Freshwater Biology 54(6):1343-1356.
• Morel, M., Tamisier, V., Pella, H., Booker, D.J., Navratil, O., Piégay, H., Gob, F., Lamouroux, N., 2019. Revisiting the drivers of at-a-station hydraulic geometry in stream reaches. Geomorphology 328, 44–56.
• Person E. 2013. “Impact of Hydropeaking on Fish and Their Habitat.” Ph.D. Ecole Polytechnique de Lausanne.
• Poff NL, Allan JD, Mark BB, Karr JR, Prestegaard KL, Richter BD, Sparks RE, Stromberg JC. 1997. “The natural flow Regime: a paradigm for river conservation and restoration” BioScience 47 (11):769–84.

Cite the thesis

Clarisse Judes. Réponses des poissons et des macroinvertébrés aux variations rapides des conditions hydrauliques à l’aval des centrales hydroélectriques gérées par éclusées. Ecologie, Environnement. Université de Lyon, 2021. Français. ⟨NNT : 2021LYSE1201⟩. ⟨tel-03638828⟩

Access manuscript on HAL thèses