Do artificial velocity refuges mitigate the physiological and behavioural consequences of hydropeaking on a freshwater Iberian cyprinid?

Abstract

The rapid flow fluctuations experienced downstream of hydropeaking facilities can alter the river hydromorphology. Given the dependence of riverine fish on physical habitat, those alterations have the potential to change the physiology and behaviour of fish. We assessed whether artificial velocity refuges mitigated the physiological and behavioural consequences of hydropeaking for the Iberian barbel (Luciobarbus bocagei). Hydropeaking trials were conducted in an indoor flume equipped with deflectors that created low flow velocity areas to serve as refuges. The FLOW‐3D was used to obtain detailed characterizations of the different velocity fields, which facilitated the interpretation of fish responses. Changes in flow magnitude and duration triggered stress responses, demonstrated by the increased blood glucose levels in the single up‐ramping event for 60 L s−1 and in the step up‐ramping event. Fish tended to seek out velocity refuges to avoid higher flow velocities and harsh hydraulic conditions at peak flows, and during the longer events. The movement behaviour frequency increased when fish were subjected to the highest peak flow (60 L s−1), particularly the individual sprints and the drifts. For the base flow (7 L s−1) and the lowest peak flow (20 L s−1) conditions, fish swam freely in the flume, whereas in the harshest hydraulic conditions they showed more difficulty in finding velocity refuges. This research presents a novel approach by combining physiology and behavioural observations with hydraulic modelling to assess the extent to which artificial flow refuges mitigate the consequences of hydropeaking. Our work serves as a model approach for future mitigation studies for fish in hydropeaking rivers.

Cover or Velocity: What Triggers Iberian Barbel (Luciobarbus Bocagei) Refuge Selection under Experimental Hydropeaking Conditions?

“…Afterwards, the upstream gate was opened to 10°, releasing the peak flow until reaching the permanent regime. The velocities in the flume [16] (i.e., 0.18 m/s for base-flow and 0.71 m/s for peak-flow) are in accordance with the suitability curves for juveniles and adults [34,40] and the sustained swimming ability [41] of L. bocagei (Table 1). As two To assess the potential of overhead cover and velocity-refuge to provide flow protection areas in hydropeaking conditions, we tested a LUNKERS-type structure, hereinafter L-structure.…”

“…Experimental flume-based research has proposed indirect measures to mitigate hydropeaking consequences. For example, lateral refuges [14], deflectors [16], substrate heterogeneity [17], and other cover structures such as velocity refuge, visual isolation and overhead cover [15] have been studied as refuge alternatives for fish during hydropeaking events. Fish refuges have been used to mitigate the displacement and changes in movement patterns caused by hydropeaking on fish [18].…”

“…Therefore, it is expected that physiological responses under hydropeaking conditions will be higher than those in base-flow conditions, though the direction and range of those responses is difficult to determine [24]. Recent studies demonstrated that hydropeaking triggers distinct physiological and behavioral responses, according to the combination of hydrodynamic conditions with the presence of lateral and instream structures (e.g., [16,25]). However, the potential of overhead cover and velocity-refuge structures to trigger physiological changes under similar conditions has not yet been tested.…”

Life Stage-Specific Hydropeaking Flow Rules

“…Only limited space availability may be the major problem for the construction of such basins. In contrast, instream velocity refuges such as deflectors require less lateral space [93]. In the very critical larval phase, a combination of compensation reservoirs and altered operational management might be most effective by avoiding over-sized reservoirs.…”

Assessment of Retrofitted Ramped Weirs to Improve Passage of Potamodromous Fish

“…Additionally, numerical modelling was performed to characterize the hydrodynamics of all the configurations tested, using the computational fluid dynamics (CFD) commercial software FLOW-3D ® . Iberian barbel was selected as the target species, since it is considered representative of a few species of medium-sized benthic potamodromous cyprinids commonly present in Iberian and Western European rivers [22,38,39]. It was expected that: (i) passage performance of fish, considering attraction as well as successful upstream movements, will be influenced by both factors Q and RD; (ii) attraction efficiency would increase with increasing Q, and with RD that provide higher velocity magnitudes; and (iii) successful passages, and consequently passage efficiency, would decrease with increasing Q and with RD presenting high turbulence and high velocity magnitude.…”