10.1 Water Masses and Seabird Distributions in 

 the Southern Chukchi Sea 



JONATHAN M. ANDREW* and J. CHRISTOPHER HANEY» 

 'Regional Office, US Fish & Wildlife Senice, Anchorage. Alaska. USA 

 'Woods Hole Oceanographic Institution. Woods Hole. Massachusetts. USA 



Introduction 



The Bering and Chukchi Seas represent highly strategic 

 territories to the countries at their margins. Fishery stocks, 

 populations of migratory wildlife, mineral resources, pollution 

 control, and navigation through international straits are among 

 the sovereignty and management concerns shared by both the 

 Soviet Union and United States. Given the recent declaration 

 of 200-mile Exclusive Economic Zones and attendant regulation 

 of resource development on outer continental shelves, both 

 countries have a strong basis for mutual cooperation and joint 

 research in these high latitude seas. 



Seabirds are among the natural resources shared by both 

 countries. Very large populations of murres, puffins, guillemots, 

 auklets, kittiwakes, and other species breed on islands in the 

 northern Bering Sea (e.g., St. Lawrence Island) and within 

 Bering Strait (e.g.. Little Diomede Island) and may forage 

 across jurisdictional boundaries (Sowls et ai. 1978; NOAA, 

 1988). In fact, the most important offshore foraging sites used 

 by seabirds from these colonies are often unknown because at- 

 sea censusing has been previously limited to the east side of the 

 International Convention Line (cf. Springer et ai. 1989). 

 Recent studies have shown that environmental gradients from 

 east to west across the northern Bering and southern Chukchi 

 Seas have profound consequences for both benthic (Grebmeier 

 et ai. 1988, 1989; Grebmeier & McRoy, 1989) and pelagic 

 food webs (Springer effl/., 1989). Variability in hydrographic 

 regimes is also thought to influence the distribution and species 

 composition of seabird colonies (e.g.. Springer et ai. 1984, 

 1 987), but no synoptic comparisons of seabirds to water masses 

 and oceanographic properties have been made across either the 

 northern Bering or southern Chukchi Seas. 



The principal objectives of the Third Joint US-USSR 

 Bering & Chukchi Seas Expedition were to characterize the 

 fundamental oceanographic, hydrochemical and 

 hydrobiological parameters of these marine ecosystems 

 (e.g.. Whitledge et al.. 1988), and to assess their capacity for 

 assimilating marine pollution (I ARPC, 1988). Main scientific 

 tasks included /. collecting biological, chemical, and physical 

 data to provide comprehensive ecological and oceanographic 

 profiles of the Bering and Chukchi Seas; 2. studying the 

 physiological and ecological characteristics of plankton 

 organisms; and 3. as.sessing the ecological health of the 

 Bering Sea. 



Here we report on marine distributions of seabirds in the 

 southern Chukchi Sea during late summer (August 1988). We 

 interpret our findings within the contexts of /. concurrent 



oceanographic measurements of both seabird and water mass 

 locations; 2. along- rather than across-shelf variability in 

 seabird abundance; and 3. the affects of colony adjacency and 

 reproductive status in detecting seabird use of water masses. 



Materials and Methods 



Study Area 



The Chukchi Sea ranges from Wrangel Island off 

 northeastern Siberia, USSR, east to Point Barrow, Alaska, and 

 south to Bering Strait (Fig. I). The study area for this cruise 

 extended from Kolyuchin Bay on the Chukchi Peninsula, 

 Soviet Union, northeastward to Cape Lisbume, Alaska, and 

 then south to the strait. The Chukchi Sea continental shelf is 

 uniformly shallow, ranging between 40 and 60 m in depth. 

 Unlike many continental shelves, the Chukchi Shelf is primarily 

 oriented east-west instead of north-south. The relatively deep 

 Barrow and Herald Canyons transect the outer continental 

 shelf margin to the north, and Herald Shoals (20-30 m sill 

 depth) dominates the north-central Chukchi seafioor. This 

 analysis was confined to the southern Chukchi Sea, where 

 bottom slopes are very slight except on immediate approach to 

 land. 



Fig. 1. Study area and bathymetry in the southern Chukchi Sea. 



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