Anaerobic metabolism during sub-maximal swimming in salmonids

The extent of anaerobic metabolism required to support sub-maximal swimming below the critical swimming speed (Ucrit) in rainbow trout (Oncorhynchus mykiss) was investigated by monitoring the concentration of lactate and phosphocreatine within the white muscle. Trout were swum to 70%, 80% and 100% of Ucrit. Lactate and phosphocreatine were measured using conventional methods, from the white muscle of exercised trout and sockeye salmon (O. nerka), and the chemical shift of inorganic phosphate (Pi) and quantity of phosphocreatine from the muscle were determined using ³¹P nuclear magnetic resonance (NMR) spectroscopy. The predictive relationship between lactate and Pi is described by the second-order regression equation: lactate (ɥmols g⁻¹ tissue)=856.38-306.67*Pi+27.80*Pi² (r²=0.834). The relationship between the phosphocreatine (PCr) estimate obtained using ³¹P-NMR and the concentration of intramuscular PCr is described by the equation: PCr (ɥmols g⁻¹ tissue)=0.562+0.021 *PCr (ppm) (r²=0.800). Estimates of lactate and PCr were obtained from trout exercised to 0% (rest), 70%, 80%) and 100% Ucrit, using these relationships. Anaerobic metabolism, as determined by lactate concentration, is required to support activity at and above 70% of Ucrit. With increasing exercise, the concentration of lactate also increased, indicating increased anaerobic metabolism. Additionally, the concentration of lactate and phosphocreatine varies along the length of the body. The energy associated with anaerobic metabolism during sub-maximal swimming was estimated and found to be significant.Science, Faculty ofZoology, Department ofGraduat