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

The main calving ground of the east Australian humpback
whale stock is defi ned to the north by the Whitsunday
Islands (Chaloupka and Osmond 1999). Simmons and
Marsh (1985) reported that calves tend to be seen north of
the latitude 21°S early in the migration during the months of
June and July.
Since 1993, the Pacifi c Whale Foundation has undertaken a
mark-recapture study using photo-identifi cation techniques.
Their study (Pacifi c Whale Foundation 1997) describes the
distribution of mother-calf pairs as being in the sheltered
waters both around and inshore of the Whitsunday island
group. However, the whales are widely dispersed with no
obvious pockets of concentration. They also conclude that
whales do not appear to be staying in the region for any
great length of time, except for mother-calf pairs.
Malcom and Duggan (1997) undertook aerial survey of
the Whitsunday Islands to determine the distribution and
abundance of humpback whales. They concluded that most
of the whales were observed south of Hook and East Black
Reef, an area were there is likely to be less disturbance of
whales because it is south of the main vessel transit route.
However, it is uncertain if this is an artefact of the small
sample size.
4.4.4 Cairns region
Anecdotal information suggests that the numbers of
humpbacks are increasing in the inshore waters of the
Cairns region.
4.4.5 Hervey Bay Marine Park
Hervey Bay (latitude 25°S) is a large shallow embayment
of approximately 4000 square kilometres, bound to the
west by the mainland and by Fraser Island to the east.
Most of the Bay is less than 18m deep and has a sand or
mud fl oor. Fraser Island, the world’s largest sand island, is
126 kilometres long. The island extends north and south
bridging the continental shelf. Smith (1997) produced a
comprehensive summary of the research undertaken and
management of Hervey Bay Marine Park.
Based on aerial and boat-based studies, humpbacks
have been found to favour the eastern part of Hervey Bay,
especially Platypus Bay, and tend to aggregate in shallow
water close to the western coast of Fraser Island (Corkeron
et al.1994; Pacifi c Whale Foundation 1993; The Oceania
Project 1999). The area offshore from the Wathumba Creek
is identifi ed as being an area that is favoured by humpbacks
(Corkeron et al.1994; The Oceania Project 1999). It is
uncertain what contributes to this aggregation but it could be
the freshwater infl uence of the creek.
Humpbacks have been recorded in Hervey Bay during the
months of July–November (The Oceania Project 1999;
Pacifi c Whales Foundation 2001). Temporal procession
of whales entering the bay is similar to that described for
the whole Group V population (Chittleborough 1965 and
Dawbin 1966). Immature humpbacks enter the Bay fi rst in
late July and mothers and calves in September, but there
is no data indicating that the Bay is of importance to any
particular age-class of the Group V population (Corkeron et
al.1994). However, the use of the Bay by mothers and calves
in September is coincident with school holidays and an
associated increase in recreational boating activity.
8 • Distribution, abundance and biology of Group V humpback whales Megaptera novaeangliae: A review • August 2002
Bryden and Corkeron (1989) estimated that approximately
30 percent of the Group V population enters Hervey
Bay each year. Corkeron et al.(1994) concluded that the
similarity between the proportion of calves observed in
Hervey Bay and the estimates of the rate of increase for the
Group V population suggests that females with calves do not
preferentially use the Bay. During September and October,
mother/calf pods move through the Bay in waves or pulses
and often stay for prolonged periods.
There are no published sightings of newborn calves in
Hervey Bay. Rather than being described as a winter
ground, Hervey Bay is considered a resting site for
humpbacks migrating south to Antarctica. There is no
information to suggest that commercial whale watching has
or has not altered the distribution of whales in Hervey Bay.
The pre-whaling distribution is unknown for this localised
area.