Regional differences in diving behavior of harbor seals in the Gulf of Alaska

Adult and subadult harbor seals (Phoca vitulina richardii (Gray, 1864); n = 108) from Southeast Alaska (SE), Kodiak Island (KO), and Prince William Sound (PWS) were instrumented with satellite data recorders to examine dive parameters for harbor seals in the Gulf of Alaska at regional and annual scales. Most dives (40%–80%) were <20 m in depth and <4 min in duration; however, dives from 50 to 150 m depth were not uncommon and dives to 508 m were recorded. PWS seals spent less time in the water during the prebreeding and breeding seasons than SE and KO seals. SE seals used a greater diversity of depths than KO and PWS seals. Only seals in PWS and SE (i) dived deeper and longer and spent more time diving in winter than during spring and summer and (ii) dived deepest during the day only in winter. Seals in all regions and seasons dived most frequently and spent the most time diving at night. Subadult seals spent more time diving, dived more often, displayed a stronger diurnal pattern with deepest dives during the day in the winter, and dived deeper than adults.