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A method for predicting harbor seal (Phoca vitulina) haulout and monitoring long-term population trends without telemetry
Natural Recource Modeling (2013)
  • Jonathan D. Cowles, Andrews University
  • Shanelle M. Henson, Andrews University
  • James Hayward, Andrews University
  • Matthew W. Chacko, Andrews University
Abstract
Monitoring population trends in harbor seals ( Phoca vit- ulina ) generally involves two steps: (i) a census obtained from aerial surveys of haul-out sites, and (ii) an upward correction based on the proportion of seals hauled out as estimated from a sample of telemetry-tagged seals. Here we present a mathematical method for obtaining site-specific correction factors without telemetry. The method also determines site-specific envi- ronmental factors associated with haulout and provides algebraic equations that predict diurnal haul-out numbers and correction factors as functions of these variables. We applied the method at a haul-out site on Protection Island, Washington, USA. The haul-out model and correction factor model were functions of tide height, current velocity, and time of day, and the haul-out model explained 46% of the observed variability in diurnal haul-out dynamics. Although the particular models are site-specific, the general model and methods are portable. A suite of such models for haul-out sites of a regional stock would allow managers to monitor long-term population trends without telemetry.
Keywords
  • Aerial survey,
  • correction factor,
  • environmental factor,
  • harbor seal,
  • haulout,
  • Marine Mammal Protection Act,
  • mathematical model,
  • Phoca vitulina,
  • population trend.
Disciplines
Publication Date
2013
Publisher Statement
Retrieved October 30, 2014. From http://onlinelibrary.wiley.com/doi/10.1111/nrm.12015/pdf
Citation Information
Jonathan D. Cowles, Shanelle M. Henson, James Hayward and Matthew W. Chacko. "A method for predicting harbor seal (Phoca vitulina) haulout and monitoring long-term population trends without telemetry" Natural Recource Modeling Vol. 26 Iss. 4 (2013)
Available at: http://works.bepress.com/james_haywardandrewsedu/9/