Modelling Temporal Variations of Physical Habitat for Brown Trout (Salmo Trutta) in Hydropeaking Conditions

Abstract

Hydropeaking generates significant fluctuations in flow in downstream river reaches, resulting in frequent and major changes in the physical conditions of the fish habitat. The microhabitat methodology, derived from the IFIM, focuses on minimum flow studies in by‐pass sections, but has been adapted to two rivers subject to daily flow fluctuations (Ance du Nord and Oriège). Application of this methodology to hydropeaking conditions requires additional habitat descriptors to take into account the temporal aspects of peaking flows and their effects on trout habitat, i.e. flow and habitat chronologies analysed in duration and frequency. Hydropeaking and the natural upstream flow regime were compared. The results show that habitat variations are closely related to the flow regime and site morphology; hydropeaking effects on habitat parameters are different in wide and in deep profiles. It is suggested that, in both instances, hydraulic refugia are crucial for organisms to withstand the variations of physical variables. This approach helps in better understanding the physical limiting factors in situations of short‐term flow fluctuations.

Attractiveness of a lateral shelter in a channel as a refuge for juvenile brown trout during hydropeaking

“…Hydropeaking negatively affects fish behavior (Heggenes et al 1996;Valentin 1996;Capra et al 2012), fish migration (Greenberg et al 1996), spawning habitats and egg development (Courret et al 2012), as well as juvenile development (for ages 0?) (Scruton et al 2005(Scruton et al , 2008).…”

“…During the peak discharge, mobilization of the riverbed sediment can damage exposed organisms and destroy habitats in the substrate interstitial spaces . The degradation of natural habitats has also been observed (Valentin 1996;Ovidio et al 2008, Gouraud et al 2008) for a bedload transport regime that was similarly highly modified (Baumann and Klaus 2003;Eberstaller and Pinka 2001). Turbidity also increases during peak flow, producing a high seepage gradient into riverine aquifers in an inner colmation of the river bed (Fette et al 2007).…”

“…This composition corresponded to a substrate preference curve that has been reported by Valentin (1996) and Vismara et al (2001) for juvenile brown trout. Preliminary tests on this loose substrate showed that during hydropeaking some juveniles hid in the spaces between the coarse gravel that were near the channel wall where velocities were somewhat lower.…”

“…characteristics of the fish that were captured by electrofishing. Brown trout is the main species found in Alpine and sub-alpine rivers and has been subject of many biological research studies on hydropeaking (Valentin 1996;Scruton et al 2003;Flodmark et al 2006;Gouraud et al 2008;Murchie et al 2008). During the experiments, groups of 10 (low density) or 20 trout (high density) were used, which resulted in a fish density of 1-2 fish/m 2 in the channel and 10-20 fish/m 2 in the refuge.…”

Habitat De La Truite Commune (Salmo Trutta L.) Pendant La Période Juvénile en Ruisseau : Préférences, Mouvements, Variations Journalières Et Saisonnières.

“…A la fin des années 80, sous l'impulsion nord-américaine, les recherches se sont orientées vers la modélisation des habitats hydrauliques (FRAGNOUD, 1987 ;SOUCHON et al, 1989 ;BELAUD et al, 1989). De nombreux développements ont suivi (notamment GINOT, 1995 ;POUILLY et al, 1995 ;BARAN, 1995 ;CAPRA, 1995 ;DELACOSTE, 1995 ;VALENTIN et al, 1996 ;LAMOUROUX, 1997 ;GOURAUD, 1999), plaçant les relations entre le poisson et son milieu au coeur des recherches actuelles sur les populations de truite.…”