Stability in The Proportion of Harbor Seals Hauled Out Under Locally Ideal Conditions

Authors

Michael Simpkins, National Marine Mammal Laboratory, NMFS/Alaska Fisheries Science Center
David Withrow, National Marine Mammal Laboratory
Jack Cesarone, National Marine Mammal Laboratory
Peter Boveng, National Marine Mammal LaboratoryFollow

Date of this Version

10-2003

Comments

Published in MARINE MAMMAL SCIENCE, 19(4):791-805 (October 2003).

Abstract

We monitored the haul-out behavior of 68 radio-tagged harbor seals (Phoca vitulina) during the molt season at two Alaskan haul-out sites (Grand Island, August-September 1994; Nanvak Bay, August-September 2000). For each site, we created a statistical model of the proportion of seals hauled out as a function of date, time of day, tide, and weather covariates. Using these models, we identified the conditions that would result in the greatest proportion of seals hauled out. Although those “ideal conditions” differed between sites, the proportion of seals predicted to be hauled out under those conditions was very similar (81.3% for Grand Island and 85.7% for Nanvak Bay). The similar estimates for both sites suggest that haul-out proportions under locally ideal conditions may be constant between years and geographic regions, at least during the molt season.