Distribution, abundance and biology of Group V humpback whales ...

Figure 3. Humpback distribution and migration routes (Anderson et al.1995)
4 Distribution
4.1 Global distribution
The humpback has a cosmopolitan distribution throughout
the world’s oceans (Figure 3). However, despite the species’
unlimited migratory potential, they exhibit signifi cant genetic
worldwide partitioning among oceanic populations and
among sub-populations or “stocks” within these oceanic
populations, and among seasonal habitats within stocks
(Baker et al.1994).
During the summer, the humpback can be found on high
latitude feeding grounds. During the winter, some individuals
migrate to low latitude temperate, tropical or sub-tropical
waters to mate and breed. However, some populations of
humpbacks are non-migratory (for example, animals in the
northern Indian Ocean).
4.2 Distribution of southern hemisphere
stocks
Southern hemisphere baleen whale stocks were defi ned in
relation to their Antarctic summer feeding concentrations
(Paterson and Paterson 1984). These feeding
concentrations correspond with areas defi ned for fi sheries
purposes; the areas are described numerically as Area I, II,
III, IV, V and VI (Figure 3). Tynan (1998) provided support
for the historical description of feeding stocks in Antarctica
through a description of the Antarctic Circumpolar Current
and an associated food web that includes humpback whales.
4.3 Distribution of Group V population
The humpbacks that migrate either side of the Australian
continent feed in Area IV and Area V; the populations are
described as Group IV and Group V respectively (Figure
4). Data gathered on commercial whaling vessels supports
the historical division of the Group V from the Group IV
population (Chittleborough 1965; Dawbin 1966; Paterson
and Paterson 1984; Findlay 1998; Mikhalev 2000).
Further support for the division of the Group V population
from the Group IV and VI is provided from a number of
contemporary studies from different disciplines such
as photo-identifi cation studies (Garrigue and Gill 1994;
Garrigue et al.2000); genetic studies (Baker et al.1994);
and acoustic studies (Gill et al.1995).
Due to some interchange between the Group IV and V
populations while on feeding grounds, the geographical
extremities separating the populations on the feeding
grounds cannot be rigidly defi ned but are considered as
being 130ºE–170ºW (Chittleborough 1965; Paterson 1991).
The southern latitudinal boundary of the wintering ground
is more diffi cult to defi ne as females are thought to calf en
route during migration (Chittleborough 1965). However,
the main calving ground for the Group V population is
considered to be the warmer lagoonal waters of the Great
Barrier Reef in an area between Port Douglas (16°S) and
Whitsunday Islands (21°S) (Paterson & Paterson 1984;
Dawbin 1956; Chittleborough 1965; Chaloupka & Osmond
1999; Garrigue et al.2000)
Several authors (Chittleborough 1965; Dawbin 1966;
Chaloupka and Osmond 1999; Garrigue et al.2000) support
the hypothesis that the Group V population separates into an
eastern group (New Zealand and the Pacifi c Islands) and a
western group (east Australian coast). Garrigue et al.(2000)
used a photo-identifi cation study to determine that there
was no interchange between individuals from the Group V
and Group VI populations found on the New Caledonia and
Tongan wintering grounds.
4.4 Distribution in Queensland
Sheltered waters of the Great Barrier Reef region are
described as an important calving area for the east
Australian humpback whale stock (Paterson and Paterson
1984; 1989; Simmons and Marsh 1985; Chaloupka and
Osmond 1999) (Figure 5). However, studies and anecdotal
evidence indicate that parturition occurs at higher latitudes
and at dispersed sites throughout Queensland waters.
Craig and Herman (2000) presented data on the preference
of sites by female humpbacks dependent upon their
reproductive status. The study hypothesised that undersea
topography has some infl uence on habitat choice made by
females on their wintering grounds.
5 • Distribution, abundance and biology of Group V humpback whales Megaptera novaeangliae: A review • August 2002