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- Title
Otolith size and location in digestive tracts of northern fur seals ( Callorhinus ursinus): Implications for dietary interpretations.
- Authors
Sinclair, E. H.; York, A. E.; Antonelis, G. A.
- Abstract
Walleye pollock ( Theragra chalcogramma) otoliths ( n= 2,706) recovered from stomachs, small intestines, and colons of 43 northern fur seals ( Callorhinus ursinus) were evaluated for size and wear by location in the digestive tract. Pollock fork length was regressed on otolith length after correction for erosion, and age was estimated from the calculated body size. Age-1+ pollock otoliths (≥6.3-mm length) were concentrated in stomachs while age-0 otoliths (≤6.2-mm length) were concentrated in colons. Less than 10% of otoliths were found in the small intestines. Pollock age decreased with progression along seal gastrointestinal tracts. Otolith quality increased along gastrointestinal tracts in numbers ≥20, which was typical of age-0 otoliths recovered from colons. Otolith distribution by age and quality along gastrointestinal tracts suggests that small (≤12 cm) schooling prey are consumed in large volume and passed as a bolus rapidly through the digestive tract before significant erosion of bony remains occurs; while larger prey are eaten in smaller volume and subjected to otolith erosion due to longer retention in the stomach. Our results illustrate the importance of multiple sampling strategies to comprehensively represent prey size in pinniped diet.
- Subjects
WALLEYE pollock; OTOLITHS; NORTHERN fur seal; GASTROINTESTINAL system; STATISTICAL sampling; BODY size
- Publication
Marine Mammal Science, 2011, Vol 27, Issue 2, p421
- ISSN
0824-0469
- Publication type
Article
- DOI
10.1111/j.1748-7692.2010.00418.x