Poor Performance of a Retrofitted Downstream Bypass Revealed by the Analysis of Approaching Behaviour in Combination with a Trapping System

Abstract

The implementation of fish downstream migration bypass systems is still a major challenge, and there is interest in validating the adequacy of different configurations of bypass devices. In the Amblève River (Belgium), a mobile 3.3-m height dam feeds two principal Francis and one Francis micro-turbine and is equipped with a modern vertical slot fish pass and a downstream bypass. The aim of this study was to test the bypass attraction and efficiency (i.e. percentage of fish that approach the entrance and use the bypass) for Atlantic salmon smolts. During three consecutive years, a total of 1346 smolts were equipped with a radio frequency identification tag and released from March to May upstream of the dam of Lorcé. The entrance of the downstream migration bypass was equipped with a radio frequency identification antenna in order to detect the smolts approaching. In 2014, a capture cage was also placed downstream the bypass to evaluate its efficiency. The mean percentage of detected smolts at the entrance varied from 26.2 to 39.7%. In 2014, 16.5% of the released smolts entered the bypass and were finally caught in the cage, representing 39% of the smolts detected at the entrance. More than 98% of the detections occurred during night (mainly between 9 PM and 3 AM). The searching delay near the bypass entrance varied from less than 5 min to more than 5 days (median 4.3 min). Visual observation indicated a behavioural reluctance before entering the bypass, with a shift from positive to negative rheotaxy. Our results underline the difficulty to install retrofitted bypass system on old existing hydropower plants.

Performance of a large partial-depth guide wall to divert downstream migrating Atlantic salmon smolts at Tuilières dam, Dordogne River

“…minimize fish injuries for individuals using this potential migration route, such as Archimedes screws or VLH (Very Low Head) turbines (Cefas, 2012;Lagarrigue, 2013;Lagarrigue and Frey, 2010). Other techniques, such as surface bypasses, associated with conventional water intake trash racks, have proven to have highly variable and generally limited efficacy (Larinier and Travade, 1999;Tomanova et al, 2018;Ovidio et al, 2017). Passage efficiency of surface bypasses is linked not only to the spacing of the bars, but also to the existence of a velocity pattern in front of the rack guiding the fish to the entrance of the bypass.…”

Masking a fish's detection of environmental stimuli: application to improving downstream migration at river infrastructure

“…() and Vowles and Kemp (). On encountering velocity gradients, downstream moving juvenile salmonids typically switch orientation to face the flow and actively reject the near‐field hydrodynamic transition by swimming back upstream; for example, Atlantic salmon smolts Salmo salar L. 1758 (Ovidio et al ., ); Pacific salmon smolts Oncorhynchus spp. (Kemp et al ., ); brown trout Salmo trutta L. 1758 (Vowles & Kemp, ).…”

“…To mitigate for these adverse effects, physical or behavioural screens are used to guide downstream migrating fish away from dangerous routes to more desirable bypass channels (Larinier, 2008). However, the efficacy of these systems is often low (Calles et al, 2012;Kynard & O'Leary, 1993), with fish avoiding conditions encountered at bypass entrances (Kynard & Buerkett, 1997) resulting in delayed migration (Ovidio et al, 2016) and increased probability of passage through hazardous routes (Johnson et al, 2000).…”

“…Numerous studies have analysed fish behaviour as they encounter velocity gradients (Enders et al, 2009(Enders et al, , 2012Haro et al, 1998;Kemp et al, 2005Kemp et al, , 2006Kemp et al, , 2008Russon & Kemp, 2011;Vowles et al, 2014), but relatively little attention has been directed at reducing rejection rates; among the exceptions are Haro et al (1998) and Vowles and Kemp (2012). On encountering velocity gradients, downstream moving juvenile salmonids typically switch orientation to face the flow and actively reject the near-field hydrodynamic transition by swimming back upstream; for example, Atlantic salmon smolts Salmo salar L. 1758 (Ovidio et al, 2016); Pacific salmon smolts Oncorhynchus spp. (Kemp et al, 2005); brown trout Salmo trutta L. 1758 .…”

The use of behavioural metrics to evaluate fishway efficiency

“…These multispecies and multistage characteristics imply that the fishways have to be efficient throughout the seasons for species with various swimming and leaping capacities, as well as different motivational states to migrate. It is thus crucial to improve the design of the fishway and to collect data from a wide range of structures typologies, in a wide variety of rivers and regions in order to find successful and more integrative solutions for the future (Cook & Hinch, ; Kemp, ; Ovidio et al, ). Studies on passage efficiency (percentage of fish present that entered and successfully moved through a fishway) have increased in the past 10 years, and efforts have been made more recently to focus on non‐commercial species such as rheophilic cyprinids (Alexandre et al, ; Branco, Santos, Katopodis, Pinheiro, & Ferreira, ; Sanz‐Ronda et al, ; Silva, Santos, Ferreira, Pinheiro, & Katopodis, and Silva, Santos, Ferreira, Pinheiro, & Katopodis, ).…”