Abundance of Harbour Porpoises in the Baltic Sea From Aerial Surveys

  • Berggren P
  • Hiby L
  • Lovell P
 et al. 
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Abstract

An aerial survey was conducted to estimate the abundance of harbour porpoises the Baltic Sea in July 2002. The survey covered about 2.25% of the approximately 20,000 nm2 (68,000 km2) survey area based on an estimated effective strip width of 268 metres. The survey area represents the currently documented distribution range of the species in the Baltic Sea. The survey was conducted along seven replicate zig-zag tracks, which were designed by using a random start point, to give a non-zero probability of covering any point in the survey area. One porpoise pod was seen on each of two of the tracks. A point estimate of the number of porpoise pods in the survey area is 93 pods. Based on an assumed negative binomial distribution for the number of pod sightings per track and incorporating the uncertainty in the estimate of effective strip width, the 95% confidence limits for the pod abundance estimate are from 10 to 460 pods

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Authors

  • P Berggren

  • L Hiby

  • P Lovell

  • M Scheidat

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