Distribution of foraging shearwaters relative to inner front of SE Bering Sea

• Published in: Marine ecology. Progress series (Halstenbek) Vol. 305; pp. 219 - 233
• Main Authors: Jahncke, J., Coyle, K. O., Zeeman, S. I., Kachel, N. B., Hunt, G. L.
• Format: Journal Article
• Language: English
• Published: Oldendorf Inter-Research 23-12-2005
• Subjects: Aggregation; Ammodytes hexapterus; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Birds; Copepoda; Crustacea; Diet; Foraging; Fundamental and applied biological sciences. Psychology; Invertebrates; Primary productivity; Puffinus tenuirostris; Sea birds; Sea water; Sea water ecosystems; Seas; Seasons; Synecology; Thysanoessa raschii; Zooplankton; Bering Sea; Pacific Ocean; North Pacific; IN, Bering Sea; Shear; Euphausiacea; shear-water; Fronts; Puffinus tenuirostris; Foraging behavior; Short-tailed; Euphausiids; Crustacea; Marine environment; Seabird foraging; Bering Sea; Vertebrata; Plankton; Arthropoda; Thysanoessa raschii; Invertebrata; Aves; Thysanoessa inermis
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps305219

We examined the hypothesis that short-tailed shearwatersPuffinus tenuirostrisaggregate to forage at the inner front of the SE Bering Sea because of enhanced production there. We tested this hypothesis by comparing primary production, the distribution of euphausiids and the distribution of shearwaters relative to the front during late spring and late summer/early fall of 1997, 1998 and 1999. We found enhanced primary production at the front and offshore of the front during summer but not during spring. Primary production varied between seasons and years. Major differences were related to anomalous conditions in 1997 and 1998. The density of euphausiids was higher at the front and offshore of the front during summer, but there were no differences among regions during spring. Foraging shearwaters aggregated in high densities at the front during summer, but foraged close to shore during spring. At the front, shearwaters foraged on euphausiidsThysanoessa raschiiandT. inermisas expected, and on copepods that accumulated in the area. The proportion of zooplankton consumed at the front decreased from summer 1997 to summer 1999, while consumption of sandlanceAmmodytes hexapterusat this feature increased. Our results show that, during summer, the inner front supports aggregations of euphausiids and their seabird predators. The means by which the frontal system supports enhanced production and the subsequent trophic transfers is dependent on the availability of nutrients at depth in the frontal region and the aggregation of small zooplankton organisms in this feature.