Diet mixing in an aquatic carnivore, the harbour seal

To determine the effects of diet mixing on digestive performance, harbour seals (Phoca vitulina L., 1758) were offered either pure diets of Pacific herring (Clupea pallasii Valenciennes, 1847) or walleye pollock (Theragra chalcogramma (Pallas, 1814)) or a 1:1 mix of herring and pollock. Regardless o...

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Bibliographic Details
Published in:Canadian Journal of Zoology
Main Authors: Trumble, Stephen J, Castellini, Michael A
Format: Article in Journal/Newspaper
Language:English
Published: Canadian Science Publishing 2005
Subjects:
Animal Science and Zoology
Ecology, Evolution, Behavior and Systematics
Pacific
harbour seal
Phoca vitulina
Theragra chalcogramma
Online Access:http://dx.doi.org/10.1139/z05-069
http://www.nrcresearchpress.com/doi/pdf/10.1139/z05-069
Description
Summary:To determine the effects of diet mixing on digestive performance, harbour seals (Phoca vitulina L., 1758) were offered either pure diets of Pacific herring (Clupea pallasii Valenciennes, 1847) or walleye pollock (Theragra chalcogramma (Pallas, 1814)) or a 1:1 mix of herring and pollock. Regardless of diet, retention time decreased approximately 40% as intake quadrupled. The mean apparent digestible dry matter (ADDM) was greatest on mixed diets during low feeding frequency trials; ADDM during high feeding frequency trials was significantly reduced as intake increased for animals on the single-species (pollock or herring) diets. As intake increased, up to 45% more digestible energy was assimilated from the mixed diet than from either single-species diet. The findings of this study suggest that a mixed diet consisting of prey differing in lipid and protein amounts increased digestible energy intake in harbour seals. Our measures of intake and ADDM in harbour seals revealed digestive flexibility and indicated that digestion in harbour seals was more efficient on a mixed diet.

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