Author(s): Yvan Bercovitz; Laurence Tissot; Pierre Sagnes; Dominique Courret; Franck Lebert; Thierry Lagarigue; Vincent Mataix; Lionel Dumond
Keywords: Downstream Migration; Sensor Fish; Salmon smolts; Waterfall
Abstract: The OFB (French Office of Biodiversity) and EDF (Electricity of France) have long collaborated on expanding knowledge about fish migration and protection measures for their downstream migration at hydropower plants (Tomanova et al. 2018). The current joint project re-examines reception conditions for fish after downstream passage through bypasses, as the criteria proposed by Odeh and Orvis (1998) are not fully satisfactory. Thus far, the study combines two types of experimental studies: (i) 4 in situ quantifications of live fish injuries, associated with (ii) evaluation of the hydraulic constraints in the reception zone using the autonomous Sensor Fish developed by the PNNL, in the same 4 in situ sites and in 13 laboratory configurations combining different flow rates and water depths in the reception zone. For each live fish experiment, 50 to 100 smolts of Atlantic salmon (137–225 mm in length) were injected in the downstream passage device and recovered after reception in the downstream zone. Fish were inspected immediately and after 48h to evaluate possible delayed injuries (scale losses, bleeding, stroke, death…). The laboratory results were acquired at an experimental waterfall called ‘Angel Jump’ at the EDF Lab (Chatou, France), which is more than 9 m high and has a maximal flowrate of 335 l.s-1. In the plunge pool, a mobile bottom allows to change water depth at the reception zone. The Sensor Fish was deployed 50 times for each in situ and laboratory experiment. The results of Sensor Fish allowed us to discriminate the harshness of the experimental conditions using the number and the intensity of collision events registered in the reception area. First comparisons with results obtained in situ with Sensor Fish and live fish test are performed. The results presented are preliminary, however some findings may already be drawn. In particular, the threshold of 95 g for expecting fish injury does not appear to be adequate to reflect in situ harsh passage conditions in reception zones for Atlantic salmon smolts. Concerning Sensor Fish, the fact that high proportions of shocks in both laboratory and in situ configurations exceeded 200 g, which is the upper value of the range specified, questions the capacity of this sensor to precisely characterize the hydraulic constraints in reception zones.