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- Title
A METHOD FOR PREDICTING HARBOR SEAL ( PHOCA VITULINA) HAULOUT AND MONITORING LONG-TERM POPULATION TRENDS WITHOUT TELEMETRY.
- Authors
COWLES, JONATHAN D.; HENSON, SHANDELLE M.; HAYWARD, JAMES L.; CHACKO, MATTHEW W.
- Abstract
Monitoring population trends in harbor seals ( Phoca vitulina) 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 environmental 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.
- Subjects
HARBOR seal; PREDICTION models; POPULATION measurement (Population biology); ALGEBRAIC equations; ENVIRONMENTAL impact analysis; TELEMETRY; AERIAL surveys
- Publication
Natural Resource Modeling, 2013, Vol 26, Issue 4, p605
- ISSN
0890-8575
- Publication type
Article
- DOI
10.1111/nrm.12015