DECAF overview and initial results

Mary Woodcock Kroble
Friday 9 November 2007
Date: 27 February 2008
Time: 4:00 pm - 5:00 pm

Speaker: Len Thomas and Tiago Marques (CREEM)


Density Estimation for Cetaceans using passive Acoustic Fixed sensors (DECAF)

The goal of this talk is to describe the project I am currently working on as part of my post-doc and some of the results obtained so far. DECAF, the project acronym, stands for “Density Estimation for Cetaceans from passive Acoustic Fixed sensors”. It is a 3 year project, built around 4 case studies: sperm whales (2 case studies) at AUTEC, beaked whales at AUTEC and humpback whales at PMRF. For all of them, the ultimate objective is density estimation.

The background for the use of passive acoustics will be discussed, contrasting this approach with visual line surveys.

Until now most of the work was related to the beaked whales case study. We started by evaluating a method previously used at AUTEC to estimate beaked whale density. This was a group counting algorithm, with several potential problems related to some arbitrary choices and a statistical artifact: these are briefly reviewed. Building on that, we have evolved into looking at two different approaches: (1) dive counting and (2) cue counting. Both of these will be described. A likelihood based method to estimate a whale location was attempted, but just recently we realized that it was not adequate, and improvements to this will be attempted next. Further, data analysis to obtain relevant parameters to carry simulation of plausible data sets to evaluate the “dive counting” approach have also been attempted, with interesting preliminary results.

Recently we have started looking into the sperm whales case study, and some general ideas about the way to address this case study will also be presented.

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