Abstract:

To continue an annual series of aerial surveys off the southern Australian coast between Cape Leeuwin WA and Ceduna SA since 1993, a survey was undertaken over five days, 23-27 August, 2017. A total of 1546 animals was sighted, including 506 calves and 4 ‘yearlings’; these include double counts, given that each flying leg is covered twice, ‘outward’ and ‘inward’. Additionally 13 humpback whales, including three calves, were recorded (Table 1). For comparison with previous years’ results, maximum counts for each leg are taken; for the 2017 survey, the comparable counts are 847 individuals of which 303 were cows accompanied by calves of the year. The 2017 counts are the highest yet in the series.

From 5603 photographic images obtained, 487 have been selected for computer-assisted ‘matching’ with those (some 9000 images of over 2000 individuals) already available in the catalogue.

Regression analysis of log number against year for 1993-2017 gives increase rates for all animals of 0.0547 (95% CI 0.0392-0.0703) equivalent to a percentage increase of 5.62 (95% CI 4.00-7.28) per annum and for cow/calf pairs of 0.0603 (95% CI 0.0382-0.0824) or 6.22 (3.89-8.59) per annum respectively.

Current population size, for this, the ‘western’ Australian subpopulation, is estimated at 2474.

A Progress Report on the 2017 survey was provided as required under the funding Agreement, on 31 December 2017.

Further funding, for three years from 2018, is now being provided by the Australian Government through the NESP Marine Biodiversity Hub, Project A7.

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