Estimating Bear Population Size in Alaska using Distance Sampling

Mary Woodcock Kroble
Wednesday 10 November 2010
Date: 27 July 2011
Time: 4:00 pm - 5:00 pm

Speaker: Earl Becker (Alaska Department of Fish and Game)


The adaptation of distance sampling to estimate bear abundance in Alaska has many unique challenges.  These surveys are conducted with small fixed-wing aircraft, the resulting distance data has maximum detection occurring away from the line transect line.  A gamma-shaped detection model (Becker and Quang 2009) that allows covariates is used to model the distance data.  The resulting covariate models will have multiple distance locations where detection is maximized, one location for each level of the covariate variables.  Mark-recapture data is used to model the probability of maximum detection.  These 2 models are combined using a point-independence model (Laake 1999, Borchers et al. 2006) to produce bear population estimates.  Progress on implementing a limiting independence model (Buckland et al. 2010), which has no independence assumptions, will also be presented. 

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