Links between hydrodynamic conditions and behaviour of downstream migrating Atlantic salmons

Links between hydrodynamic conditions and behaviour of downstream migrating Atlantic salmons

© @ULiège

This project investigates the effect of hydrodynamic conditions on the downstream migration of fish. Over the last decades, numerous studies have established the negative impact of dams and hydropower plants on the aquatic life. These infrastructures fragment rivers and limit fish passage. Their impact result in injuries, deaths, delayed migrations of fish and, in extreme cases, in the disappearance of an entire species. Despite the existence of validated solutions such as fish ladders for upstream fish passage, the migration in the opposite direction remains problematic as it has been less studied. Therefore, this doctoral project aims at providing a rational characterization of salmon behaviours depending on hydrodynamic variables, and then at paving the way for evidence-based design of effective mitigation solutions to restore fish migration possibilities at run of the river hydropower schemes in order to both decrease the negative impact river damming and improve the ecological status of anthropized rivers.

As laboratory experiments on fish are subject to environmental biases related to the artificial conditions of the equipment, the project uses telemetric data to reproduce smolts behaviour. These data are obtained from monitoring campaigns of young Atlantic salmons in rivers conducted either by the Unit of Management of Aquatic Resources and Aquaculture (UGERAA) of the University of Liège or by the PROFISH company. Regarding the hydrodynamic conditions, numerical models are used to simulate and obtain the hydraulic conditions available to smolts throughout their downstream migration. The two databases are then combined and analysed using statistical methods to characterize and explain observed fish behaviours as a function of hydraulic variables. Based on the statistically established relationships, several criteria and practical solutions will be proposed to biologist and engineering communities to improve the rapid migration of smolts in rivers. At the end of this thesis, we hope to establish a robust method that can be replicated not only on other rivers but also on other aquatic species.