Abundance estimates of Breeding Stock ‘D’ Humpback Whales from aerial and land-based surveys off Shark Bay, Western Australia, 2008

Single platform aerial line transect and land-based surveys of Breeding Stock ‘D’ humpback whales Megaptera novaeangliae were undertaken to provide absolute abundance estimates of animals migrating northward along the western Australian coast. The aerial survey flew a total of 28 flights, of which 26 were completed successfully, from 24th June-19th August 2008. The land-based survey was undertaken from Cape Inscription, Dirk Hartog Island, during the expected peak of the whales’ northward migration, from 8th-20th July. During the first week of the land-based survey, some double count effort was undertaken to provide information on the numbers of pods missed from the land station. The assumed period of northward migration was 2nd June-7th September. Estimated abundance of northward-migrating whales during that time is 21,750 (95% CI: (17,550-43,000)). This estimate is based on an estimate of relative abundance of surface-available whales of 11,850 (9,550-23,450), and an estimated g(0) of 0.54 (±0.21).