Humpback population

Project: A comparison of group IV humpback whale population estimates from two key locations along the Western Australian coast – implications for future survey location and methodology

The goal of this study is to assess the current status of the humpback whale population that migrates along the western Australian coastline each year. This project aims to fill significant gaps in current knowledge by employing the latest statistical techniques to analyse seven years of survey data from North West Cape (NWC) to estimate sex ratio, population densities and size; and to compare results to those from Shark Bay, ~400 km south of NWC. By addressing these needs the proposed project will, in addition, elucidate on current survey design efficacy and practicality; which will have implications for future and ongoing locations and methodologies for monitoring humpback whales.

study regions
Study regions where long term data sets on humpback whale counts have been collected using aerial surveys; Shark Bay (bottom blue circle) and North West Cape (upper blue circle
survey of area
Survey tracks in the region of North West Cape region, Western Australia. Image: Courtesy of C. Jenner

Specific objectives

  • Identify the variability in density estimates resulting from data collected at various time intervals and migratory phases past North West Cape (~4 to 12 week time intervals over the northern and southern migratory phases).
  • Produce humpback whale density estimates at North West Cape using aerial survey data sets collected in 2000, 2001, 2006, 2007, and 2008.
  • Estimate the population increase rate for Group IV humpback whales based on density estimates at North West Cape.
  • Compare density estimates at North West Cape to those at Shark Bay for surveys made in overlapping years (2008).
  • Compare estimates of population size increase rates at North West Cape (over 2000, 2001, 2006, 2007, 2008) to those made at Shark Bay (1999, 2005, 2008).
  • Determine sampling bias in sex ratio estimates made at North West Cape from biopsies collected during boat surveys in 2002 and 2003; and
    1. Determine the implications for future study.
    2. Correct sex ratio for biases.
    3. Determine the implications of corrected sex ratio estimates to the estimated population size.
  • Report the following to the 2010/11 International Whaling Commission (IWC):
    1. population size estimates,
    2. corrected sex ratio, and
    3. implications of the results for optimal survey location and methodology for estimating the Group IV humpback whale population size.

Shark Bay estimates (of which we compare our North West Cape estimates to) were done by J. Bannister (WA Museum), S. Hedley (Uni St. Andrews), C. Paxton (Uni St. Andrews, and R. Dunlop (University of Queensland). The project is being conducted in collaboration with Centre for Whale Research, (WA) Inc., and Uni. of St. Andrews.