Seabird distribution, abundance and diets in the eastern and central Aleutian Islands

George L Hunt,K O Coyle,J Jahncke

doi:10.1111/j.1365-2419.2005.00372.x

George L Hunt, K O Coyle + Show 1 more

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https://doi.org/10.1111/j.1365-2419.2005.00372.x

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Abstract

AbstractWe examined the hypothesis that seabird distribution, abundance and diets differ among the eastern and central Aleutian Islands in response to distinct marine environments and energy pathways in each region. Research cruises were conducted in June 2001 and May–June 2002. We determined the distribution, abundance, diet and prey consumption of seabirds, and related these to zooplankton abundance and water masses that possess different physical properties. We found that distribution, abundance and diets of seabirds could be partitioned into two regions that correspond to marine environments determined by the extent of the Alaska Coastal Current along the eastern and central Aleutian Islands. Short‐tailed shearwaters (Puffinus tenuirostris) were the most abundant seabird in the coastal waters of the eastern Aleutian Islands, and northern fulmars (Fulmarus glacialis) were the most abundant seabird in the oceanic waters of the central Aleutian Islands. Seabird communities in the central and eastern Aleutian Islands were likely associated with different food webs. In the central Aleutian Islands, short‐tailed shearwaters and northern fulmars consumed shelf‐break species of euphausiids (Thyssanoesa longipes) and oceanic copepods (Neocalanus cristatus), respectively; in the eastern Aleutian Islands, both short‐tailed shearwaters and northern fulmars consumed shelf species of euphausiids (T. inermis). Carbon transport to seabirds was highest in Unimak and Akutan Passes where shearwaters removed large quantities of shelf euphausiids, followed by Samalga and Seguam Passes where northern fulmars removed large amounts of oceanic copepods.

Highlights

The Aleutian Islands are formed by the highest peaks of the submerged Aleutian ridge, between which waters flow from the North Pacific Ocean and the Bering Sea (Favorite, 1974)
Marked changes in physical properties of the water observed around Samalga Pass in 2001 and 2002 (Ladd et al, 2005a) showed that the Aleutian Archipelago could be divided into two distinct marine environments that extend over a much larger geographical scale than that determined solely by the local availability of shelf habitat (Springer et al, 1996)
The distributions and abundances of the two dominant seabird species could be partitioned into two regions that corresponded to the marine environments determined by the extent of the Alaska Coastal Current

Summary

Introduction

The Aleutian Islands are formed by the highest peaks of the submerged Aleutian ridge, between which waters flow from the North Pacific Ocean and the Bering Sea (Favorite, 1974). The upper ocean circulation on the North Pacific side of the Aleutian Islands is characterized by the westward flow of the Alaskan Stream and the Alaska Coastal Current, and on the Bering Sea side by the eastward flow of the Aleutian North Slope Current (Favorite, 1974; Reed and Stabeno, 1999; Ladd et al, 2005a; Stabeno et al, 2005) Within the passes, both northward and southward tidal flow occurs (Reed, 1971; Favorite, 1974; Ladd et al, 2005a), but the overall net flow of water through the passes is northward (Reed, 1990; Stabeno et al, 2005).

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