Anaerobic and aerobic energy production of young rainbow trout (Salmo gairdneri) during and after bursts of activity

Summary

• 1. Anaerobic and aerobic energy production during and after induced bursts of maximum swimming activity were measured in four size classes of rainbow trout fry at 4, 12 and 20°C.

• 2. The rate of phosphocreatine (PCr) utilization during burst activity appeared independent of size and temperature. On average the concentration of PCr dropped from 5.8±1.0 to 1.5±0.7 μmol·g⁻¹ within 30 s of stimulation, and decreased only slightly more after an additional 30 sec of stimulation. The concentration of ATP also decreased to 70% of control levels, whereas the concentrations of ADP and AMP remained constant, in agreement with other investigations on vertebrate white muscles. Lactate concentrations did not change during the shorter period of stimulation but from then on increased steadily through the second half of the one minute stimulus and through the recovery period observed (10 min).

• 3. Five minutes after the end of stimulation phosphocreatine had recovered 67% of the control level whereas the concentration of ATP as well as the energy charge remained low. After ten minutes not only phosphocreatine but also ATP and energy charge had recovered at least 80% of the ground lost during the period of exertion.

• 4. The following parameters of aerobic energy production were distinguished:Routine rate ($\dot V_{O_2 }$r): maintained for several hours before or after induced burst activity;maximum rate ($\dot V_{O_2 }$max): attained for a few minutes during and immediately after an induced burst of activity;net recovery $\dot V_{O_2 }$: amount of oxygen consumed during recovery time minus the amount due to routine rate during this interval.

• 5. The routine rate of$\dot V_{O_2 }$ is affected by temperature but less so by the age of the fry. On the other hand,$\dot V_{O_2 }$max and net recovery,$\dot V_{O_2 }$ increased strongly with age at the two lower temperatures. Aerobic scope for activity increases with size and is maximum at 12°C.

• 6. The age-dependent changes of$\dot V_{O_2 }$ are discussed in relation to the differentiation of the swimming musculature and to hydrodynamic changes, since between a body length of 1 and 10 cm, the fish move through a range of Reynolds numbers from approximately 10² to 10⁴.

• 7. It appears, furthermore, that with increasing size, more energy is liberated during the recovery period than would be required for repapying the true oxygen debt. This may be due to an elevated activity during poststimulus excitement.