Behavioural and physiological responses of brook trout Salvelinus fontinalis to midwinter flow reduction in a small ice-free mountain stream

Abstract

This study presents an experimental analysis of the effects of midwinter flow reduction (50-75%, reduction in discharge in 4 h daily pulses) on the physical habitat and on behaviour and physiology of overwintering brook trout Salvelinus fontinalis in a small mountain stream. Flow reduction did not result in significant lowering of temperature or formation of surface or subsurface ice. The main findings were (1) daily movement by S. fontinalis increased (c. 2·5-fold) during flow reduction, but was limited to small-scale relocations (<10 m). (2) Undercut banks were the preferred habitat and availability of these habitats was reduced during flow reduction. (3) Although both experimental and reference fish did lose mass and condition during the experiment, no effects of flow reduction on stress indicators (blood cortisol or glucose) or bioenergetics (total body fat, water content or mass loss) were detected, probably because access to the preferred type of cover remained available. Like other salmonids, S. fontinalis moves little and seeks physical cover during winter. Unlike many of the more studied salmonids, however, this species overwinters successfully in small groundwater-rich streams that often remain ice-free, and this study identifies undercut banks as the critical winter habitat rather than substratum cover.

Changes in migratory fish communities and their health, hydrology, and water chemistry in rivers of the Athabasca oil sands region: a review of historical and current data

“…A potential increase in evapotranspiration due to an increase in air temperatures in the region over the past decades may have also contributed to the decline in discharge (Schindler and Donahue 2006). Decrease in discharge can affect the availability and distribution of suitable fish habitat in streams (e.g., Krimmer et al 2011), which may indirectly affect fish through changes in the thermal regime, water chemistry, and decreases in invertebrate drift (Dewson et al 2007). …”

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

“…In cases where the stressor persists over time, deleterious effects on overall fish performance (escaping predators, finding refuge, and foraging) and in specific life‐cycle stages (reproduction and growth) will likely occur (Barton, ; Pankhurst, ). Although changes in the blood physiology have occurred in down‐ramping conditions (Arnekleiv, Urke, Kristensen, Halleraker, & Flodmark, ; Flodmark et al, ; Krimmer et al, ), the flow conditions which trigger the stress response and the extent to which their severity may cause long‐term deleterious effects remain unknown. Studies conducted in the field or in laboratory conditions assert that the absence of a physiological response after a severe flow component fluctuation indicates that fish were seeking out velocity refuges (i.e., flow refuging), although this possibility has not been properly assessed (Arnekleiv et al, ; Flodmark et al, ; Taylor et al, ).…”

Diel activity and foraging mode of juvenile Arctic charr in fluctuating water flow

“…Rapid fluctuations in water flow can also affect temporal aspects of stream fishes behaviour, for example, small and large-scale movements, relocation, and habitat use (Korman & Campana, 2009;Krimmer, Paul, Hontela, & Rasmussen, 2011;Riley, Maxwell, Pawson, & Ives, 2009;Scruton et al, 2005;Taylor et al, 2014). Other studies have suggested that salmonids also alter their diel feeding activity in response to hydropeaking (e.g., Rocaspana, Aparicio, Vinyoles, & Palau, 2016).…”