A respirometric analysis of fuel use during aerobic swimming at different temperatures in rainbow trout (oncorhynchus mykiss)

James D. Kieffer, Derek Alsop, Chris M. Wood

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Instantaneous fuel usage at 5 °C or 15 °C was assessed by measurement of rates of 02 consumption (M(O2)), CO2 excretion (M(CO2)) and nitrogenous waste excretion (M(nitrogen) =ammonia-N + urea-N) in juvenile rainbow trout (Oncorhynchus mykiss) at rest and during swimming at 45 % and 75 % of aerobic capacity (U(crit)). After 2 weeks of training at approximately 1 body length s-1 (BL s-1), critical swimming speeds (approximately 3.0BLs-1) and wholebody energy stores (total protein, lipids and carbohydrates) were identical in fish acclimated to 5 °C or 15 °C. M(O2) and N(CO2) increased with swimming speed at both temperatures and were higher at 15 °C than at 5 °C at all speeds, but the overall Q10 values (1.23-1.48) were low in these long-term (6 weeks) acclimated fish. The respiratory quotient (M(CO2)/M(O2), approximately 0.85) was independent of both temperature and swimming speed. In contrast to M(O2) and M(CO2) the rate of ammonia excretion was independent of swimming speed, but more strongly influenced by temperature (Q10 1.4-2.8). Urea excretion accounted for 15-20 % of M(nitrogen), was unaffected by swimming speed and showed a tendency (P<0.07) to be positively influenced by temperature at one speed only (45 % U(crit)). Nitrogen quotients (NQ M(nitrogen)/M(O2)) were generally higher in warm-acclimated fish, remaining independent of swimming speed at 15 °C (0.08), but decreased from about 0.08 at rest to 0.04 during swimming at 5 °C. Instantaneous aerobic fuel use calculations based on standard respirometric theory showed that both acclimation temperature and swimming speed markedly influenced the relative and absolute use of carbohydrates, lipids and proteins by trout. At rest, cold-acclimated trout used similar proportions of carbohydrates and lipids and only 27 % protein. During swimming, protein use decreased to 15 % at both speeds while the relative contributions of both lipid and carbohydrate increased (to more than 40 %). On an absolute basis, carbohydrate was the most important fuel for fish swimming at 5 °C. In contrast, resting fish acclimated to 15 °C utilized 55 % lipid, 30 % protein and only 15 % carbohydrate. However, as swimming speed increased, the relative contribution of carbohydrate increased to 25 %, while the protein contribution remained unchanged at approximately 30 %, and lipid use decreased slightly (to 45 %). On an absolute basis, lipid remained the most important fuel in fish swimming at 15 °C. These results support the concept that lipids are a major fuel of aerobic exercise in fish, but demonstrate that the contribution of protein oxidation is much smaller than commonly believed, while that of carbohydrate oxidation is much larger, especially at higher swimming speeds and colder temperature.

Original languageEnglish (US)
Pages (from-to)3123-3133
Number of pages11
JournalJournal of Experimental Biology
Issue number22
StatePublished - Nov 1 1998


  • Aerobic swimming
  • Carbohydrate
  • Fuel
  • Lipid
  • Nitrogen quotient
  • Oncorhynchus mykiss
  • Protein
  • Rainbow trout
  • Respiratory quotient
  • Temperature

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)


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