Go with the flow: integrating dynamic and thermal regimes in regulated river management

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Go with the flow: managing rivers for migratory fish facing fragmentation and climate change

Publication . Mameri, Daniel Chagas Roquette; Santos, José Maria; Ferreira, Maria Teresa; Schmutz, Stefan

ABSTRACT - Rivers harbour approximately 1100 migratory fish species, facing barriers to free movement, whether they are physical (dams and weirs) or determined by unfavourable habitat conditions. The main goal of this thesis was to evaluate the effect of flow and thermal changes in rivers caused by flow regulation, while also considering the ongoing climate change, to fish passability and swimming behaviour. This thesis is structured in a total of six chapters, with an introduction to the theme (Chapter 1) and four original works, including: (1) two case studies where fish passability through barriers equipped with a fishway was evaluated, in relation to different flows and other environmental variables (Chapter 2) and assuming different discharges under distinct climate change predictions (Chapter 3); and (2) two experimental studies, where swimming behaviour and activity were assessed in response to previous exposure to an experimental heatwave (Chapter 4) and rapid flow fluctuations as a consequence of hydropower generation (hydropeaking), coupled with abrupt thermal variations – cold thermopeaking (Chapter 5). Results from the first two chapters suggest that fishway efficacy is strongly dependant not just on a suitable flow regime (minimum ecological flows may be insufficient under drought scenarios), but also on other favourable habitat conditions such as water temperature, triggering upstream migration. In the experimental designs that were conducted, activity and boldness in juvenile barbel Luciobarbus bocagei were lower after exposure to a heatwave under laboratory conditions; for the other experimental study, the drift of nase Chondrostoma nasus larvae increased with cold thermopeaking. These results highlight the importance of ensuring suitable thermal regimes in rivers, namely by protecting sites that can act as thermal refugia for the most vulnerable life stages of migratory fish, and by monitoring and adjusting flow releases in dams to ensure that water temperature downstream does not change significantly

2023Tese de doutoramento

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Programa de financiamento

OE

Número da atribuição

PD/BD/142885/2018