Thermal sensitivity of metabolic rates and swimming performance in two latitudinally separated populations of cod, <Emphasis Type="Italic">Gadus morhua</Emphasis> L. |
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Authors: | Eve-Lyne Sylvestre Dominique Lapointe Jean-Denis Dutil Helga Guderley |
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Institution: | (1) Département de biologie, Université Laval, Québec, QC, Canada, G1K 7P4;(2) Institut National de la Recherche Scientifique, Centre Eau,Terre et Environnement, Université du Québec, 490 rue de la Couronne, Québec, QC, Canada, G1K 9A9;(3) Institut Maurice-Lamontagne, Pêches et Océans Canada, 850 route de la Mer C.P. 1000, Mont-Joli, QC, Canada, G5H 3Z4 |
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Abstract: | Atlantic cod populations live in a wide thermal range and can differ genetically and physiologically. Thermal sensitivity
of metabolic capacity and swimming performance may vary along a latitudinal gradient, to facilitate performance in distinct
thermal environments. To evaluate this hypothesis, we compared the thermal sensitivity of performance in two cod stocks from
the Northwest Atlantic that differ in their thermal experience: Gulf of St Lawrence (GSL) and Bay of Fundy (BF). We first
compared the metabolic, physiological and swimming performance after short-term thermal change to that at the acclimation
temperature (7°C) for one stock (GSL), before comparing the performance of the two stocks after short-term thermal change.
For cod from GSL, standard metabolism (SMR) increased with temperature, while active metabolism (AMR, measured in the critical
swimming tests), EMR (metabolic rate after an exhaustive chase protocol), aerobic scope (AS) and critical swimming speeds
(U
crit and U
b–c) were lower at 3°C than 7 or 11°C. In contrast, anaerobic swimming (sprint and burst-coasts in U
crit test) was lower at 11 than 7 or 3°C. Factorial AS (AMR SMR−1) decreased as temperature rose. Time to exhaustion (chase protocol) was not influenced by temperature. The two stocks differed
little in the thermal sensitivities of metabolism or swimming. GSL cod had a higher SMR than BF cod despite similar AMR and
AS. This led factorial AS to be significantly higher for the southern stock. Despite these metabolic differences, cod from
the two stocks did not differ in their U
crit speeds. BF cod were better sprinters at both temperatures. Cod from GSL had a lower aerobic cost of swimming at intermediate
speeds than those from BF, particularly at low temperature. Only the activity of cytochrome C oxidase (CCO) in white muscle
differed between stocks. No enzymatic correlates were found for swimming capacities, but oxygen consumption was best correlated
with CCO activity in the ventricle for both stocks. Overall, the stocks differed in their cost of maintenance, cost of transport
and sprint capacity, while maintaining comparable thermal sensitivities. |
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Keywords: | Metabolic rate U crit swimming Burst swimming Thermal sensitivity Temperature |
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