The effects of water temperature and ammonia concentration on swimming capacity of brook charr (Salvelinus fontinalis, Mitchill, 1814) were determined by measuring gait transition speed (U(gt), cms(-1)), maximum burst speed (U(max), cms(-1)), tail-beat amplitude (a, cm), tail-beat frequency (f, Hz), maximum acceleration of bursts (A(max), cms(-2)), number of bursts, distance of bursts (cm) and total swimming distance (cm) in a 4.5m long experimental raceway with increasing upstream water velocity. Temperatures other than the acclimation temperature of 15 degrees C significantly reduced swimming characteristics of gait transition, i.e. U(gt) and A(max), while increased ammonia concentration reduced the measures of swimming after U(gt): U(max), the relationship between f and swimming speed above U(gt), a, A(max) and the distance travelled with each swimming burst above U(gt). This study, using a novel raceway set-up shows various effects of temperature and ammonia exposure on the swimming performance of brook charr and can be used to establish threshold values for environmental management.
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