[MARMAM] NEW PAPER - humpback whale abundance estimates from Western Australia

Phil Bouchet phil.bouchet at uwa.edu.au
Tue Jul 17 22:50:18 PDT 2012


Dear colleagues,

We are pleased to announce the publication of the following paper in the Journal of Cetacean Research and Management (apologies for cross-postings):

Salgado Kent, C., Jenner, K.C.S., Jenner, M.-N., Bouchet, P., Rexstad, E. (2012). Southern Hemisphere breeding stock "D" humpback whale population estimates from North West Cape, Western Australia. Journal of Cetacean Research and Management, 12(1):29-38.

ABSTRACT:
Estimates of the abundance of Breeding Stock D humpback whales (Megaptera novaeangliae) are key to the conservation and management of what is thought to be one of the largest populations of the species. Five years (2000, 2001, 2006, 2007 and 2008) of aerial surveys carried out over an eight-year period at North West Cape (Western Australia) using line transect methodology allowed trends in whale numbers to be investigated, and provided a base for comparison with estimates made approximately 400km south at Shark Bay (Western Australia). A total of 3,127 whale detections were made during 74 surveys of the 7,043km2 study area west of NWC. Pod abundance for each flight was computed using a Horvitz-Thompson like estimator and converted to an absolute measure of abundance after corrections were made for estimated mean cluster size, unsurveyed time, swimming speed and animal availability. Resulting estimates from the migration model of best fit with the most credible assumptions were 7,276 (CI = 4,993-10,167) for 2000, 12,280 (CI = 6,830-49,434) for 2001, 18,692 (CI = 12,980-24,477) for 2006, 20,044 (CI = 13,815-31,646) for 2007, and 26,100 (CI = 20,152-33,272) for 2008. Based on these data, the trend model with the greatest r2 was exponential with an annual increase rate of 13% (CI = 5.6%-18.1%). While this value is above the species' estimated maximum plausible growth rate of 11.8%, it is reasonably close to previous reports of between 10-12%. The coefficient of variation, however, was too large for a reliable trend estimate. Perception bias was also not accounted for in these calculations. Based on a crude appraisal which yielded an estimated p(0) of 0.783 (from independent observer effort, CV = 0.973), the 2008 humpback population size may be as large as 33,300. In conclusion, the work here provides evidence of an increasing Breeding Stock D population, but further surveys are necessary to confirm whether the population is indeed increasing at its maximum rate.

PDF copies are available upon request to phil.bouchet at uwa.edu.au

All the best,

Phil Bouchet - on behalf of the first author Dr Chandra Salgado Kent and co-authors

Phil Bouchet | PhD candidate
Centre for Marine Futures - Oceans Institute The University of Western Australia (M470), 39 Fairway Road, Crawley, WA 6009, Australia
Tel: +61 (8) 6488 8118 | Mob: +61 (0) 406 811 113
Email: phil.bouchet at uwa.edu.au




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