Influence of seasonal temperature on the repeat swimming performance of rainbow troutOncorhynchus mykiss

Abstract

). Given that metabolic recovery in skeletal muscle (muscle lactate, ATP and glycogen, but not PCr) occurs more rapidly at warm than cold temperatures in exhausted rainbow trout Oncorhynchus mykiss and Atlantic salmon Salmo salar (Kieffer et al., 1994;Wilkie et al., 1997;Kieffer, 2000), the expectation is that swimming performance is restored faster at a higher temperature. This expectation would be consistent with the known increase in both maximum oxygen uptake and maximum cardiac output with temperature (e.g. Butler et al., 1992;Farrell, 1997;Taylor et al., 1997) because an improved oxygen delivery system could support a more rapid recovery of the metabolic debt incurred with exhaustive exercise. However, when Atlantic salmon were angled rather than chased to exhaustion, muscle glycogen, intracellular pH and lactate were restored more rapidly under cold conditions than warm conditions (Wilkie et al., While the temperature dependence of exercise performance in fishes is reasonably well documented, information on the temperature dependence of metabolic recovery and reperformance is scant. This study examined the recovery of swimming performance after exhaustive exercise in rainbow trout Oncorhynchus mykiss at seasonal temperatures ranging from 5 to 17°C and explored the relationship between performance and preceding metabolic state. The primary objective of the study was to test the hypothesis that increased temperature increases the capability of rainbow trout to repeat a critical swimming speed (U crit), as assessed by two consecutive critical swimming speed tests separated by a 40·min rest interval. An additional expectation was that certain plasma ionic, metabolic and humoral parameters would be correlated with how well fish reperformed and so plasma levels of lactate, potassium, ammonia, osmolality, sodium and cortisol, as well as hematocrit, were monitored before, during and after the swim challenges via an indwelling cannula in the dorsal aorta. As expected, performance in the first Ucrit test (Ucrit1) was positively related to temperature. However, the relationship between Ucrit1 and reperformance (Ucrit2) was not dependent on acclimation temperature in a simple manner. Contrary to our expectations, Ucrit2 was less than Ucrit1 for warmacclimated fish (14.9±1.0°C), whereas Ucrit2 equaled Ucrit1 for cold-acclimated fish (8.4±0.9°C). Cold-acclimated fish also exhibited a lower Ucrit1 and less metabolic disruption compared with warm-acclimated fish. Thus, while warm acclimation conferred a faster Ucrit1, a similar swimming speed could not be attained on subsequent swim after a 40·min recovery period. This finding does not support the hypothesis that the ability of rainbow trout to reperform on U crit test is improved with temperature. Both plasma lactate and plasma potassium levels were strongly correlated with Ucrit1 performance. Therefore, the higher Ucrit1 of warm-acclimated fish may have been due in part to a greater anaerobic swimming effort compared with cold-acclimated fish. In fact, a significant co...

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Subclinical Listonella anguillarum infection does not impair recovery of swimming performance in rainbow trout Oncorhynchus mykiss

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