g., Chittleborough 1961, Dawbin 1966, Robbins et al. 2011). On their annual migration, they segregate into at least seven low latitude breeding areas, which are widely distributed around oceanic islands and specific coastal regions proximate to continental shelf areas (Mackintosh 1965). With no continental barriers to movement while on feeding grounds, there U0126 clinical trial is the potential for permanent migration among populations as described for other marine megafauna (Bonfil et al. 2005, Boyle et al. 2009). Recent studies have shown relatively low levels of differentiation between neighboring humpback whale populations in the Southern Hemisphere (Baker et al. 1998a, Olavarría

et al. 2007, Rosenbaum et al. 2009, Cypriano-Souza et al. 2010). Two recognized populations of humpback whales occur along the coasts of Australia. One migrates along the eastern seaboard and is thought to mate and calve

within the Great Barrier Reef (Smith et al. 2012), the other migrates along the western seaboard and mates and calves off the Kimberley coast of western Australia (Jenner et al. 2001). During the 20th century, Australian humpback whales were hunted along both the eastern and western migratory corridors and intensively in their Antarctic feeding grounds (Mackintosh 1965). By the time commercial whaling ceased screening assay in 1963, the western Australian population was estimated to be fewer than 500 animals, down from approximately 17,000 prior to 1934 (Chittleborough 1965, Bannister 1994), and the eastern Australian population was reduced to as few as 100 individuals, down from a preexploitation abundance estimate of between 16,022 and 22,957 (Chittleborough 1965, Paterson et al. 1994, Jackson et al. 2008). Recent data have shown that both populations are recovering strongly with the current rate of increase at about 10%–11% per annum (Noad et al. 2011, Paxton et al. 2011, Salgado Kent et al. learn more 2012). Absolute abundance for western Australian humpback whales is currently estimated at 21,750 (95% CI 17,550–43,000) (Hedley

et al. 2011) and 14,522 (95% CI 12, 777–16,504) for eastern Australia (Noad et al. 2011). Although the approximate migration routes and distribution of breeding activity is reasonably well described for the two Australian populations, the degree of connectivity is less known. During the 1950s and 1960s stainless steel “Discovery” marks were shot into whales, some of which were later recovered when the whales were killed and flensed (Mackintosh 1965, Dawbin 1966). These studies showed that whales from the separate breeding grounds mix in Antarctica, and there were even two cases where individuals moved between breeding grounds (see below), but it is difficult from such data to estimate the magnitude of gene flow or whether the populations are likely to be demographically independent.