Atlantic salmon (Salmo salar) in the regulated River Alta: effects of altered water temperature on parr growth

Abstract

The chief objective of this study was to analyse the effects of altered water temperature, due to the hydropower regulation of the River Alta, on growth of Atlantic salmon parr. The river was developed for hydroelectric purposes in 1987. A 110 m high concrete dam was built in the main river 49 km upstream from the outlet to the sea. The outlet of the power station is located 2.5 km downstream from the dam. The annual regime of water temperature has been altered downstream from the power station because of the regulation. It has decreased 1-2°C during June, July and the first half of August, while it has increased up to 3°C during late summer. During winter, water temperature has increased from 0°C to about 0.3-0.4°C. Atlantic salmon is the predominant fish species in the river. They can penetrate 46 km from the sea, up to the outlet of the power station.In this paper I have studied the relationship between growth of juvenile Atlantic salmon and water temperature in the upper part of the river. At similar temperatures, the growth rate of salmon parr in the River Alta is higher in early summer than later in the growing season. In early summer the salmon grew faster than the maximum rate predicted by a recently published model. Therefore, I adjusted the model to describe growth rates of salmon in early summer (ice break to mid-August), using data derived prior to the hydropower development (1981)(1982)(1983)(1984)(1985)(1986)).The new model proved effective at describing growth rates of fish in early summer following the hydropower development (1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996). After development, growth rates decreased during early summer, but increased correspondingly later in the season. There was close agreement between these growth changes and the altered annual regime of river temperature. Overall, only minor changes in annual growth rates have been observed after the hydropower development.

Variability in stream discharge and temperature: a preliminary assessment of the implications for juvenile and spawning Atlantic salmon

“…They suggest that the basic, underlying timing of certain salmon life stages has a strong heritable component suggesting that local genetic adaptation may affect the timing of certain activities (Stewart et al, 2002). In the Girnock Burn, it has been shown that local genotype is a direct effect on growth performance (Jordan and Youngson, 1991), but, unsurprisingly, most of the variability in the growth of juvenile salmon (ca. 85%) can be accounted for by variability in stream temperatures (Bacon et al, 2005).…”

“…When high discharges do occur soon after hatch time (e.g. in 1997/1998 and 1999/2000) there may be marked effects on recruitment, foraging and growth rates (Jensen, 2003).…”

“…A number of studies have investigated the influence of stream discharge on different phases of the salmon's life-cycle (e.g. Økland et al, 2001;Jensen, 2003). For stream resident salmonids, discharge can exert a strong influence on general behaviour including foraging (e.g.…”

The influence of riparian woodland on stream temperatures: implications for the performance of juvenile salmonids

“…Instead, gross variability in fish performance appeared consistent with inter-site variability in fry density where higher densities resulted in lower growth. This highlights one of the problems of investigating fish performance under field conditions where performance is often influenced by factors other than temperature, including density (as seen here) and food availability (Jensen, 2003;Bacon et al, 2005;Gurney et al, 2008). Such factors confound simple temperature-growth relationships, especially in short-term studies, where atypical conditions can confound parameter estimates.…”

Implications of climate change on flow regime affecting Atlantic salmon

“…Minns et al, 1995;Gilvear et al, 2002), water temperature (e.g. McCarthy and Houlihan, 1996;Jensen, 2003), water quality (Winfield et al, 2004), predation (Gilvear et al, 2002), exploitation and management. A full literature review on the implications of climate change for Atlantic salmon forms part of the SWURVE project and is presented in Winfield et al (2004).…”