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Humpback whales (Megaptera novaeangliae) seasonally migrate between their corresponding breeding and feeding grounds; however, some individual whales deviate from this pattern migrating to different breeding or feeding grounds. Here, we report the first recorded movement of a humpback whale between the Antarctic Peninsula and the east coast of Australia. The individual whale, a known female, was identified by natural markings in the Antarctic Peninsula feeding area, and then photographed 15 years later in Byron Bay, on the eastern coast of Australia. This constitutes the longest migration for any humpback whale documented to date in the South Pacific Ocean and in the Southern Hemisphere (143° of longitude). Although the route is uncertain and the cues may be environmental, social or demographic, or some combinations thereof, this exceptional movement between two distant Breeding Stocks in the South Pacific Ocean demonstrates that longitudinal long-distance migrations among humpback whale populations do take place, at least occasionally, and perhaps may not be as atypical as it has been thought. [ABSTRACT FROM AUTHOR]

In understanding the impact of commercial whaling, it is important to estimate the mixing of low latitude breeding populations on Antarctic feeding grounds, particularly the endangered humpback whale populations of Oceania. This paper estimates the degree of genetic differentiation among the putative populations of Oceania (New Caledonia, Tonga, the Cook Islands and French Polynesia) and Australia (western Australia and eastern Australia) using ten microsatellite loci and mtDNA, assesses the power of the data for a mixed-stock analysis, determines ways to improve statistical power for future studies and estimates the population composition of Antarctic samples collected in 2010 south of New Zealand and eastern Australia. A large proportion of individuals could not be assigned to a population of origin (> 52%) using a posterior probability threshold of > 0.90. The mixed-stock analysis simulations however, produced accurate results with humpback whales reapportioned to their population of origin above the 90% threshold for western Australia, New Caledonia and Oceania grouped using a combined mtDNA and microsatellite dataset. Removing the Cook Islands, considered a transient region for humpback whales, from the simulation analysis increased the ability to reapportion Tonga from 86% to 89% and French Polynesia from 89% to 92%. Breeding ground sample size was found to be a factor influencing the accuracy of population reapportionment whereas increasing the mixture or feeding ground sample size improved the precision of results. The mixed-stock analysis of our Antarctic samples revealed substantial contributions from both eastern Australia (53.2%, 6.8% SE) and New Caledonia (43.7%, 5.5% SE) [with Oceania contributing 46.8% (5.9% SE)] but not western Australia. Despite the need for more samples to improve estimates of population allocation, our study strengthens the emerging genetic and non-genetic evidence that Antarctic waters south of New Zealand and eastern Australia are used by humpback whales from both eastern Australia and the more vulnerable breeding population of New Caledonia, representing Oceania. [ABSTRACT FROM AUTHOR]