Seasonal Response of Juvenile Atlantic Salmon to Experimental Hydropeaking Power Generation in Newfoundland, Canada

Abstract

Variable hydropower production leads to hydropeaking, which causes discharge fluctuations that are potentially harmful to aquatic organisms. In this study, an experimental approach was used to investigate hydropeaking effects and associated hydraulic and habitat conditions on the home range and movement of juvenile Atlantic salmon Salmo salar. Prior studies examined the responses of Atlantic salmon and brook trout Salvelinus fontinalis to experimental hydropeaking during summer and autumn. The present study focused on Atlantic salmon, involved more rapid and extreme discharge manipulation, and included winter experiments to reflect influences of reduced temperature, ice conditions, and seasonal differences in behavior and habitat selection. Experiments were conducted over a range in discharge (0.5-5.0 m 3 /s) that resulted in dramatic habitat changes in the wide, shallow, boulder-strewn study reach. Experiments were repeated in summer and winter; however, the winter range in discharge was narrower due to constraints on water release. Fish response was monitored using manual telemetry in both seasons, and fixed telemetry was used to monitor fine-scale diel winter movements. Atlantic salmon had larger home ranges and were more mobile during all flow conditions and over diel cycles in summer than in winter, and there was anecdotal evidence of stranding in isolated pools in summer. Stream morphology, in addition to the magnitude of discharge change, was an important determinant of the propensity to move. In our study, there were considerable refugia from increased velocity and dewatering, which may have reduced the need to move. In winter, fish remained relatively sedentary in comparison with the summer foraging period, and this behavior may increase the likelihood for dewatering, stranding, and freezing. A secondary concern with hydropeaking regimes is the energetic cost to fish of moving to find suitable habitats, and during summer this cost could affect stored energy reserves, which could, in turn, affect overwinter survival.

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

“…(Scruton et al 2005(Scruton et al , 2008). Significant differences between modified and natural flowing rivers have been observed in terms of the abundance and distribution of some sensitive invertebrate taxa, fish diversity and the energy base of the food web (Smokorowski et al 2011).…”

“…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.…”

Wet-season effects on the distribution of juvenile pigeye sharks, Carcharhinus amboinensis, in tropical nearshore waters

“…Some predatory fish species have been documented to move greater distances and use more space at times of high freshwater flow (de Morais and Raffray 1999; Scruton et al 2005). Increased movement and home-range expansion during the wet season was attributed to greater amounts of water available, and to individuals needing to move greater distances to locate adequate prey.…”

Distribution and movement of domestic rainbow trout, Oncorhynchus mykiss, during pulsed flows in the South Fork American River, California

“…In contrast, the longitudinal displacement of larger fish seems less likely due to their increased swimming performance, compared with smaller fishes (Webb 1971), unless there are velocity refugia that are more accessible to smaller-sized fish. Field studies have found no consistent effect of sudden, extreme peaking flows on area use or movements by adult trout and salmon (Bunt et al 1999;Gido et al 2000;Scruton et al 2005;Heggenes et al 2007). …”