Seasonal and inter-annual oceanographic changes induce diet switching in a piscivorous seabird

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 393:273-284 (2009) - DOI: https://doi.org/10.3354/meps08192 Seasonal and inter-annual oceanographic changes induce diet switching in a piscivorous seabird Motohiro Ito1,*, Hiroshi Minami2, Yuzan Tanaka1, Yutaka Watanuki1 1Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido, 041-8611, Japan 2National Research Institute of Far Seas Fisheries, 5-7-1 Shimizu, Shizuoka, 424-8633, Japan *Email: m-ito@fish.hokudai.ac.jp ABSTRACT: The structure of a marine food web can change quickly within seasons as well as inter-annually in response to physical oceanographic changes. In this study, we examined the relationship between temporal changes in the marine ecosystem of northern Hokkaido, Japan, and diets of rhinoceros auklets Cerorhinca monocerata breeding in this region. To obtain an integrated measure of changes in diet composition on short (days) and inter-annual (2004 and 2005) time scales, we used a 2-pronged approach. We examined (1) the diets of adults using stomach contents and stable isotope signatures in tissues, and (2) chick diets using the composition of bill-loads delivered to chicks. During the incubation period, the diet of adults comprised euphausiids (Thysanoessa longipes and T. inermis). During the chick-rearing period, the diet of adults was age 0 Japanese sandlance Ammodytes personatus and age 0 Japan Sea greenling Pleurogrammus azonus in the early period, but switched quickly (<10 d) to warm-water-preferring Japanese anchovy Engraulis japonicus when the warm Tsushima Current intruded into their foraging range. Adult blood plasma stable isotope ratios reflected these seasonal changes in stomach content. Diets did not differ between age categories. Furthermore, the timing of diet switching to anchovy differed inter-annually, and was about 10 d later in 2005 than 2004, reflecting a difference in the timing of the intrusion of warm water. We conclude that rhinoceros auklets respond sensitively to current-related rapid marine food web changes. KEY WORDS: Prey switching · Stable isotope signatures · Rhinoceros auklets · Anchovy · Tsushima Current Full text in pdf format PreviousNextCite this article as: Ito M, Minami H, Tanaka Y, Watanuki Y (2009) Seasonal and inter-annual oceanographic changes induce diet switching in a piscivorous seabird. Mar Ecol Prog Ser 393:273-284. https://doi.org/10.3354/meps08192 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 393. Online publication date: October 30, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.