A common environment experiment was conducted to assess the magnitude of the difference in growth, consumption,
activity rate, and spatial and temporal patterns of habitat use between morphologically different populations of
Arctic char (Salvelinus alpinus) originating from two Norwegian lakes. These two lakes contrasted sharply in terms of surface
area, depth, elevation, length of the winter period, and fish community structure (presence–absence of brown trout,
Salmo trutta). The experimental framework encompassed four littoral enclosures (average volume, 146 m3) stocked with
char from either of the two populations with duplicated treatments. Char morphology was quantified with numerical image
analysis, food consumption was estimated using caesium analysis (133Cs), and activity cost and patterns were determined
using video cameras. Char populations were morphologically distinct and reacted differently in growth (1.9-fold difference
between populations), food consumption (3-fold difference), and spatial activity patterns (20-fold difference) to the conditions prevailing in the enclosures. The results highlight that functional differences between morphologically distinct char
may drive important differences in their bioenergetic and behavioural responses when exposed to similar environmental
conditions. Such functional differences should be incorporated when developing habitat or trophic cascade models.
2010. Vol. 67, 580-595 p.