Multistate measurements of genotype interchange between East Australia and Oceania (IWC breeding sub-stocks E1, E2, E3 and F) between 1999 and 2004

Humpbacks breeding in East Australia (E1) and Oceania (New Caledonia E2, Tonga E3 and French Polynesia F) in the South Pacific are thought to be demographically independent, due to significant differentiation of mitochondrial DNA haplotypes between regions, and notable differences in the trend and pattern of recovery across the South Pacific. Matching of fluke photo-identification and microsatellite genotypes collected across the South Pacific has revealed multiple inter-annual movements between breeding grounds. Total documented movements within Oceania are greater than those documented between Oceania and East Australia, which indicates that East Australia may be more isolated from Oceania than the breeding grounds within Oceania are from each other. A strong contrast in population trend between these regions further supports this observation. A large microsatellite genotype dataset of 1,393 individuals (819 males and 574 females) spanning 1999-2004 is available from all South Pacific breeding grounds. We use this to build the first multistate movement model for the South Pacific region and to estimate rates of inter-breeding ground interchange in a framework that accounts for capture probabilities and survival through time. Thirteen inter-annual, inter-strata movements were identified; 10 males and 3 females. The data are too sparse to permit strong inference regarding movement among breeding grounds. However they do suggest that movements between East Australia and New Caledonia (Oceania) are not significantly different from intra-Oceania movements between New Caledonia and Tonga, indicating that population connectivity levels between East Australia, New Caledonia and Tonga are of similar, low magnitude, despite a pronounced difference in population trend between the East Australia and Oceania regions over the survey period. These results should be taken into consideration when grouping New Caledonia, Tonga and French Polynesia as a single unit for assessment since such an assessment may fail to account for different patterns of recovery and trend within the South Pacific.

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