ABSTRACT: In 1993, we analyzed 742 regurgitant samples of nestling double-crested cormorants Phalacrocorax auritus from 10 colonies in Penobscot Bay, Maine, USA. A total of 21 species of fish were identified from otoliths. Further, we recovered 15 fish stomachs from regurgitant samples 14 of which contained otoliths. We compared lengths of otoliths for a given taxon represented in both regurgitants and fish stomachs recovered from regurgitants, and found no significant difference. We concluded that otoliths occurring in regurgitant samples can result from secondary consumption (i.e. the consumption of a prey fish containing otoliths in its stomach). Further, we caution that the use of otoliths in diet analyses of double-crested cormorants can inflate estimates of species percent occurrence and number.

KEY WORDS: Secondary consumption . Cormorants . Regurgitants . Otoliths

Published in MEPS Vol. 123 (1995) on July 20
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1995