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Aquatic Biology

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AB 3:147-154 (2008)  -  DOI:

Buoyancy does not affect diving metabolism during shallow dives in Steller sea lions Eumetopias jubatus

A. Fahlman1,*, G. D. Hastie1,3, D. A. S. Rosen1, Y. Naito2, A. W. Trites1

1Marine Mammal Research Unit, Fisheries Centre, Room 247, AERL—Aquatic Ecosystems Research Laboratory, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
2National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173-8515, Japan
3Present address: Sea Mammal Research Unit, Gatty Marine Laboratory, University of St Andrews, St Andrews, Fife KY16 8LB, UK

ABSTRACT: Changes in buoyancy due to seasonal or abnormal changes in body composition are thought to significantly affect the energy budget of marine mammals through changes in diving costs. We assessed how changes in body composition might alter the foraging efficiency of Steller sea lions Eumetopias jubatus by artificially adjusting the buoyancy of trained individuals. PVC tubes were attached to harnesses worn by Steller sea lions that had been trained to feed at fixed depths (10 to 30 m) and to resurface inside a metabolic dome. Buoyancy was altered to simulate the naturally occurring differences in body composition reported in adult females (~12 to 26% subcutaneous fat). Diving characteristics (transit times and time at depth) and aerobic energy expenditure (gas exchange) were measured. We found that foraging cost decreased with the duration of the dive and increased with dive depth. However, changes in body composition did not affect the diving metabolic rate of Steller sea lions for dives between 10 and 30 m. We propose that Steller sea lions may adjust their diving lung volume to compensate for changes in buoyancy to avoid additional metabolic costs.

KEY WORDS: Body composition · Diving physiology · Marine mammal · Diving lung volume

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Cite this article as: Fahlman A, Hastie GD, Rosen DAS, Naito Y, Trites AW (2008) Buoyancy does not affect diving metabolism during shallow dives in Steller sea lions Eumetopias jubatus. Aquat Biol 3:147-154.

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