The influence of hydroelectric power generation on the body composition of juvenile Atlantic salmon

Abstract

The fat and protein content, and thus energy resources of young (parr) Atlantic salmon (Salmo salar) were examined in a temperate river. Juvenile salmon exhibited distinct seasonal patterns of energy storage and use. The lowest levels of energy were found towards the end of winter (mean mass specific energy about 4.3 kJÁg À1). There was a rapid accumulation of fat in spring/ early summer in spite of low-water temperatures (highest mean content of mass specific energy of about 5.0 kJÁg À1 in June). By early autumn (August) there was a rapid depletion of fat and energy resources. The decline in specific energy during late summer was of the same magnitude as the corresponding winter decline. Furthermore, total fat and protein content, and thus energy resources of juveniles below a hydroelectric power plant (hydrostation (HS)) differed from those at a (lower) reference station (RS). The younger fish exhibited higher gains, but also larger losses of energy resources compared to corresponding values at the RS. Specifically during the summer, young of year (YOY) had 31% lower total energy content at the regulated site (mean 1.27 kJ per individual) than the RS (mean 1.84 kJ). Higher mortality may occur at the site most affected by the hydroelectric plant, where energy resources on average were higher, but where depletion was also most severe.

Variation of juvenile Atlantic salmon (Salmo salar) body composition along sedimentary links*

“…The influence of distinct fluvial habitat types over smaller spatial scales is however less documented. Similarly, other studies have reported differences in lipid content of rainbow trout juveniles (Oncorhynchus mykiss Walbaum) reared in different tributaries (Dedual 2002) and of juvenile Atlantic salmon originating from sites differing in water temperature (Berg et al 2006). Interesting trends in the body composition were observed but our initial hypothesis, that fish of the upstream sections have higher energy content, was nevertheless not verified.…”

“…salmon. Similarly, other studies have reported differences in lipid content of rainbow trout juveniles (Oncorhynchus mykiss Walbaum) reared in different tributaries (Dedual 2002) and of juvenile Atlantic salmon originating from sites differing in water temperature (Berg et al 2006). On the other hand, a study found a similar body composition between two Atlantic salmon populations living in tributaries with different abiotic conditions (temperature and flow velocity) but with a comparable biological context (fish densities and benthic biomass) (Riddell & Leggett 1981).…”

“…While many previous studies have covered the variations in the proximate body composition of wild juvenile salmonids at specific locations through time (Gardiner & Geddes 1980;Berg & Bremset 1998;Dedual 2002;Morgan et al 2002;Dempson et al 2004;Berg et al 2006;Naesje et al 2006), only little information is available on the spatial variations related to habitats conditions (Dedual 2002;Dempson et al 2004;Berg et al 2006). Differences in the body composition of adult and juvenile Atlantic salmon (Salmo salar L.) originating from contrasting environments such as riverine ⁄ estuarine and fluvial ⁄ lacustrine habitats have been previously observed (Cunjak et al 1990;Jonsson et al 1997).…”

“…Interesting trends in the body composition were observed but our initial hypothesis, that fish of the upstream sections have higher energy content, was nevertheless not verified. Given the wide range of habitat types used by juvenile salmonids, spatial variations in body composition could potentially be as important as the seasonal component in the energetic dynamic of a population (Gardiner & Geddes 1980;Berg et al 2006). Trends in the body constituents were different between age-classes and rivers, whereas they were highly variable within-and among-samples.…”

“…For juvenile salmonids, energy acquired through feeding is allocated for processes such as maintenance, somatic growth, overwinter survival and early maturation or smoltification (Jonsson & Jonsson 1998;Post & Parkinson 2001;Morgan et al 2002;Dempson et al 2004). Proximate body composition is the direct consequence of the allometric relationships of feeding and metabolism, the activity levels, life-history strategy and the spatio-temporal variations in biotic and abiotic factors (Gardiner & Geddes 1980;Berg & Bremset 1998;Jonsson & Jonsson 1998;Dedual 2002;Morgan et al 2002;Dempson et al 2004;Berg et al 2006). The influence of seasonal variations of these factors is especially evident in temperate and sub-Arctic regions where lipids are stored during summer to be mobilised during winter when food is scarce (Gardiner & Geddes 1980;Berg & Bremset 1998;Finstad et al 2004;Naesje et al 2006).…”