Abstract
Domesticated brown trout Salmo trutta parr were subjected to increased, variable flow under controlled experimental conditions. Using geometric morphometric analyses, K¯(a mass–length index) and caudal fin area–body length ratio, this study assessed morphological responses in lateral body depth, growth and robustness and propulsive potential, respectively, of parr over the course of 32 weeks. Geometric morphometric analyses did not reveal an effect of exercise on either lateral body depth or caudal fin area. However, improved overall robustness and growth trajectories in exercised parr showed a positive adaptive response to the enriched habitat. Exercise and habitat heterogeneity thus have the potential to improve survivability of domesticated salmonids in the wild.
Highlights
Global warming driven by human-induced, accelerated climate change is predicted to threaten the persistence of unprecedented numbers of terrestrial and aquatic species (IPCC, 2013, 2014)
Brown trout Salmo trutta L. 1758 reared in hatcheries have shorter heads and are less streamlined compared with individuals from natural rearing habitat (Vehanen & Huusko, 2011), while hatchery reared Atlantic salmon Salmo salar L. 1758 parr have smaller heads, smaller rayed fins and narrower caudal peduncles than their wild counterparts (Fleming et al, 1994; but see Poole et al, 2003)
This was partly confirmed by the results from linear discriminant analysis (LDA): the coefficients from linear discriminants 1 and 2, cumulatively explaining 88.33% of variance in the data (Table 1) were most strongly associated with principal components (PC) 1 and 3, respectively (Table 2)
Summary
Global warming driven by human-induced, accelerated climate change is predicted to threaten the persistence of unprecedented numbers of terrestrial and aquatic species (IPCC, 2013, 2014). Exposure to experimentally increased water flow caused young-of-the-year S. trutta to become slightly more streamlined compared with individuals reared in a slow-flowing environment, whereas S. salar grew more robust in shape when exposed to high flow (Pakkasmaa & Piironen, 2000). These results were observed after a short exposure to increased flow, demonstrating the high potential for developmental plasticity in these species (Pakkasmaa & Piironen, 2000). We hypothesized that water flow would induce a change in overall fish robustness, but due to the aforementioned ambiguity in results from previous studies the directionality of this effect could not confidently be predicted
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