ABSTRACT: Laboratory experiments investigated the effect of temperature, voluntary swimming speed and feeding behaviour on the respiration rate of adult pilchard Sardinops sagax. Mean routine respiration was 0.178 +/- 0.055 mg O₂ g^-1 wet wt h^-1. Respiration rate increased exponentially with temperature, and the mean Q₁₀ over the temperature range 10 to 22*C was 1.82 +/- 0.35. Significant linear relationships were established between respiration rate and voluntary swimming speed for non-feeding, filter-feeding and particulate-feeding activities. Particulate-feeding was the most energetically expensive activity state. Swimming speed was the primary determinant of respiration rate when filter-feeding, whereas swimming speed and feeding intensity were equally important in determining respiration rate when particulate-feeding. That filter-feeding is energetically cheaper than particulate-feeding for this species supports previous work suggesting that pilchard is primarily a filter-feeder. Results presented here contrast with those for Cape anchovy Engraulis capensis, a species for which filter-feeding is energetically more expensive than particulate-feeding. Possible reasons for this difference are discussed. Calculation of a mean RQ (respiratory quotient) of 0.955 +/- 0.099 for pilchard indicates that this species catabolises both protein and carbohydrate.

KEY WORDS: Sardinops sagax . Planktivorous fish . Respiration rate . Feeding behaviour . Q₁₀ . RQ

Published in MEPS Vol. 129 (1995) on December 14
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1995