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Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet Peter Boveng, Josh London and Robert Montgomery Polar Ecosystems Program.

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Presentation on theme: "Strong Seasonal Dynamics of Harbor Seals, an Upper-Trophic Predator in Cook Inlet Peter Boveng, Josh London and Robert Montgomery Polar Ecosystems Program."— Presentation transcript:

1 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 Alaska Marine Science Symposium 2007 Photo: Michael Cameron

2 Major funding provided by Minerals Management Service, Alaska OCS Region 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 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

3 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 Alaska Marine Science Symposium 2007 Photo: Michael Cameron

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

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6 Shelikof Strait Afognak Island

7 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? Questions:

8 Cook Inlet Study Area Gulf of Alaska Kachemak Bay Kamishak Bay

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

10 Seasonal Abundance Ashore Pupping & molting periods

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

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

13 October Numbers much lower and less aggregated throughout the study area

14 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

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

16 SDRs deployed on: 40 Males 37 Females 77 Total

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18 Winter Movements

19 Spring Movements

20 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.

21 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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