Post-Breeding Season Migrations of a Top Predator, the Harbor Seal (Phoca vitulina richardii), from a Marine Protected Area in Alaska

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  • Marine protected areas (MPAs) are increasingly being used as a conservation tool for highly mobile marine vertebrates and the focus is typically on protecting breeding areas where individuals are aggregated seasonally. Yet movements during the non-breeding season can overlap with threats that may be equally as important to population dynamics. Thus understanding habitat use and movements of species during the non-breeding periods is critical for conservation. Glacier Bay National Park, Alaska, is one of the largest marine mammal protected areas in the world and has the only enforceable protection measures for reducing disturbance to harbor seals in the United States. Yet harbor seals have declined by up to 11.5%/year from 1992 to 2009. We used satellite-linked transmitters that were attached to 37 female harbor seals to quantify the post-breeding season migrations of seals and the amount of time that seals spent inside vs. outside of the MPA of Glacier Bay. Harbor seals traveled extensively beyond the boundaries of the MPA of Glacier Bay during the post-breeding season, encompassing an area (25,325 km²) significantly larger than that used by seals during the breeding season (8,125 km²). These movements included the longest migration yet recorded for a harbor seal (3,411 km) and extended use (up to 23 days) of pelagic areas by some seals. Although the collective utilization distribution of harbor seals during the post-breeding season was quite expansive, there was a substantial degree of individual variability in the percentage of days that seals spent in the MPA. Nevertheless, harbor seals demonstrated a high degree of inter-annual site fidelity (93%) to Glacier Bay the following breeding season. Our results highlight the importance of understanding the threats that seals may interact with outside of the boundaries of the MPA of Glacier Bay for understanding population dynamics of seals in Glacier Bay.
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  • Womble JN, Gende SM (2013) Post-Breeding Season Migrations of a Top Predator, the Harbor Seal (Phoca vitulina richardii), from a Marine Protected Area in Alaska. PLoS ONE 8(2): e55386.
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  • 8
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  • 2
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  • Funding and logistical support was provided by the National Park Service (NPS)-Natural Resource Preservation Program (Project# 35747), Glacier Bay National Park & Preserve, the NPS Coastal Cluster Program, the Alaska Fisheries Science Center-National Marine Mammal Laboratory-Polar Ecosystem Program, the Alaska Department of Fish & Game, the Alaska Sealife Center, and the United States Fish & Wildlife Service. JNW was supported by a Horace M. Albright-Conrad L.Wirth Fellowship through the National Park Foundation, the Oregon State University (OSU) Hatfield Marine Science Center Mamie Markham Research Fellowship, the OSU Marine Mammal Institute, the OSU Pinniped Ecology Applied Research Laboratory, the OSU Department of Fisheries & Wildlife Munson Wildlife Fellowship, and NPS NRAC Professional Development Grants. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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