The effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis)
To investigate the effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis), we measured the following: (1) the resting oxygen consumption rate $$ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{rest}}}} } \right) $$, critical swimming speed (Ucrit) and active oxygen consumption rate $$ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} } \right) $$ of fish at acclimation temperatures of 10, 15, 20, 25 and 30 °C and (2) the $$ \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $$, Ucrit and $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$ of both exercise-trained (exhaustive chasing training for 14 days) and control fish at both low and high acclimation temperatures (15 and 25 °C). The relationship between Ucrit and temperature (T) approximately followed a bell-shaped curve as temperature increased: Ucrit = 8.21/{1 + [(T − 27.2)/17.0]2} (R2 = 0.915, P < 0.001, N = 40). The optimal temperature for maximal Ucrit (8.21 BL s−1) in juvenile qingbo was 27.2 °C. Both the $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$ and the metabolic scope (MS, $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} - \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $$) of qingbo increased with temperature from 10 to 25 °C (P < 0.05), but there were no significant differences between fish acclimated to 25 and 30 °C. The relationships between $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$ or MS and temperature were described as $$ {\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} = 1,214.29/\left\{ {1 + \left[ {\left( {T - 28.8} \right)/10.6} \right]^{2} } \right\}\;\left( {R^{2} = 0.911,\;P < 0.001,\;N = 40} \right) $$ and MS = 972.67/{1 + [(T − 28.0)/9.34]2} (R2 = 0.878, P < 0.001, N = 40). The optimal temperatures for $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$ and MS in juvenile qingbo were 28.8 and 28.0 °C, respectively. Exercise training resulted in significant increases in both Ucrit and $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$ at a low temperature (P < 0.05), but training exhibited no significant effect on either Ucrit or $$ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $$ at a high temperature. These results suggest that exercise training had different effects on swimming performance at different temperatures. These differences may be related to changes in aerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen, imbalances in ion fluxes and stimuli to remodel tissues with changes in temperature.