Australia's last great whale haven.pdf - Ningaloo Atlas

Australia’s Last Great Whale Haven Appendix 1 – Species Profiles
68
Sei whale
Family
Balaenopteridae
Distribution and migration
Infrequently recorded in Australian waters. No systematic
surveys in Australian waters. Sighted opportunistically
during aerial surveys for blue whales in the Bonney
upwelling. The movements and distributions
unpredictable and not well documented. May have the
same general pattern of migration as most other baleen
whales, although a little later and to lower latitudes.
Diet and behaviour
Feed intensively between the Antarctic and subtropical
convergences, mature animals may feed in higher
latitudes. Feed on copepods and amphipods, including
krill (Euphausia superba). Feed by swimming
horizontally near the surface skimming pelagic
crustaceans unlike other rorquals. Side lunge feeding
has been observed in Antarctica. Sink rather than dive.
Information from the NW Region
Thought to occur infrequently in the region.
Scientific Name
Balaenoptera borealis
Habitat
Australian Antarctic waters and temperate, cool mainland
waters are important feeding grounds. Sightings in the
Bonney Upwelling area indicate that this area may be an
important feeding ground. Breeding occurs in tropical
and subtropical waters.
Reproduction
Sexual maturity: 6–8 years, 12.9–13.9m (males),
7.5–8.35 years, 13.8–14.4m (females). Maximum length:
19.5m female, maximum age 65. Natural mortality rates
probably (instantaneous mortality) 0.063–0.070 (males),
0.084–0.088 (females). Breeding season April – August,
Gestation: 10.5–12.5 months. Ovulation rate 0.63–0.68,
true pregnancy rate 0.41–0.43. There are no known
mating or calving areas in Australian waters.
Population status
No reliable estimates of population size. Insufficient
information to describe population structure.
Populations severely depleted by commercial whalers
in the past; minimum estimate of 165,168 killed in the
Southern Hemisphere.
Sources: Bannister et al. 94 , DEH 119 , DEWR 126 , DSEWPaC 175 , Jefferson et al. , Morrice et al. , Parker , Watkins and Schevill