Ringed Seal (<I>Phoca hispida</I>) Use of Subnivean Structures in the Alaskan Beaufort Sea During Development of an Oil Production Facility

Abstract

We investigated whether ringed seal (Phoca hispida) use of breathing holes and lairs (structures) during winter and spring was affected by construction and drilling on Northstar Island, built in the nearshore Alaskan Beaufort Sea. Trained dogs searched the sea ice for structures within 3.5 km of Northstar during each of three survey periods: November/December 2000, March 2001, and May 2001. Temperature sensors were placed in 54 different ringed seal structures to determine dates of abandonment. Ringed seals created and used sea ice structures within 11 to 3,500 m of Northstar activities. Of the 35 structures located in November and December 2000, 68% had been abandoned by late May 2001. Of the 60 structures located in March 2001, 42% had been abandoned by late May 2001. During all surveys combined, 181 structures were located, and 118 (65%) were actively used by late May 2001. We used Cox regression to determine three primary factors influencing the abandonment of these structures: (1) structures found during later searches were significantly less likely to be abandoned; (2) structures in areas of higher ice deformation were significantly more likely to be abandoned; and (3) structures farther from the ice road to Northstar were more likely to be abandoned, though marginally significant. We would have predicted structures closer to Northstar would have been abandoned at higher rates if Northstar activities negatively affected seal use of structures. Ringed seals in the Alaskan Beaufort Sea appear to create and abandon structures throughout the winter and spring at rates higher than previously documented.