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Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet

Alaska Marine Science Symposium 2007. Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet. Peter Boveng, Josh London and Robert Montgomery Polar Ecosystems Program National Marine Mammal Laboratory NOAA Alaska Fisheries Science Center Seattle, Washington

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Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet

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  1. Alaska Marine Science Symposium 2007 Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet Peter Boveng, Josh London and Robert Montgomery Polar Ecosystems Program National Marine Mammal Laboratory NOAA Alaska Fisheries Science Center Seattle, Washington peter.boveng@noaa.gov Photo: Michael Cameron

  2. Ori Badajos Steve Baird John Bengtson Michael Cameron Bob Caruso Shawn Dahle Jennifer De Groot Kim Donahue Millie Gray L.A. Holmes John Jansen Steve Jeffries Beth Jenkinson Shawn Johnson Chuck Monnett Brian Murphy Ray Outlaw Scott Pegau Julie Richmond Cy St. Amand Mike Simpkins Steve Trumble Jay Ver Hoef Dave Withrow Peregrine Falcon Marine Wayward Wind Seafood Northwind Aviation Commander Northwest Suburban Air Express People & merchants of Homer, Alaska Major funding provided by Minerals Management Service, Alaska OCS Region

  3. Alaska Marine Science Symposium 2007 Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet Peter Boveng, Josh London and Robert Montgomery Polar Ecosystems Program National Marine Mammal Laboratory NOAA Alaska Fisheries Science Center Seattle, Washington peter.boveng@noaa.gov Photo: Michael Cameron

  4. Distribution of Harbor Seals Alaska Bering Sea Distribution and abundance ashore in August is well known

  5. Shelikof Strait Afognak Island

  6. Questions: What is the abundance and distribution of seals ashore at other times of year? What is the distribution of seals at sea, and what areas are most important for foraging? What physical and biological characteristics of terrestrial and marine habitats are related to the seasonal abundance and distribution of harbor seals ashore and at sea?

  7. Study Area Kachemak Bay Cook Inlet Kamishak Bay Gulf of Alaska

  8. Aerial Surveys • June, August, October & April • June 2003 – October 2005 • ~1 week during diurnal low tides • Daily replication • GPS-linked digital photos

  9. Seasonal Abundance Ashore Pupping & molting periods

  10. June Moderate to high numbers along west shore, with very high numbers concentrated in Kachemak and Kamishak Bays

  11. August Seals more aggregated along west shore, with very high numbers concentrated in Kachemak, Kamishak, and Iniskin Bays, Big River, and southern Augustine Island

  12. October Numbers much lower and less aggregated throughout the study area

  13. April Similar to October, with concentrations beginning to rebuild in Kachemak Bay Montgomery, RA et al. In press. Spatial modeling of harbor seal use of haul-out sites in Cook Inlet, Alaska. MEPS

  14. Satellite-linked dive recorders (SDRs) Sep 2004 May 2005 Sep 2005 May 2006 Cook Inlet • Argos geolocation • Dive depth & duration • Hourly haul-out timelines

  15. SDRs deployed on: 40 Males 37 Females 77 Total

  16. Winter Movements

  17. Spring Movements

  18. Foraging Areas • State-space Kalman filtered tracks are analyzed to provide kernal density estimates for time spent in each pixel. • Densities aggregated from multiple seals will be compared with relevant physical and biological data to identify important determinants of foraging habitat.

  19. Conclusions • A strong seasonal pattern in numbers of harbor seals ashore reflects constraints imposed by the annual life history events of reproduction and molting • When not constrained by these life history events, harbor seals spend much more time in the water and range more widely • Although foraging patterns vary widely among individuals, we suppose that the aggregate spatial patterns of time spent at sea will reflect variations in characteristics of the marine habitat (workshop to be hosted at KBRR in Homer)

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