Seasonal Distribution of the Fin Whale (Balaenoptera physalus) in Antarctic and Australian Waters Based on Passive Acoustics

Abstract

The fin whale is listed as globally vulnerable, with ongoing threats to their population, yet little is known about the distribution and movements of the Southern Hemisphere sub-species, Balaenoptera physalus quoyi. This study assesses fin whale distribution in the Southern Hemisphere analysing acoustic recordings from 15 locations in Antarctic and Australian waters from 2002 to 2019. A seasonal acoustic presence of fin whales in Antarctic waters from late austral summer to autumn (February to June) with long-term, consistent annual usage areas was identified at the Southern Kerguelen Plateau and Dumont d’Urville sites. In comparison, limited vocal presence of fin whales was observed at the Casey site. In Australian waters, fin whales were seasonally present from austral autumn to mid-spring (May to October) on east and west coasts, with a decadal pattern of acoustic presence observed at Cape Leeuwin, WA. Two migratory pathways are identified, from the Indian sector of Antarctica to the west coast of Australia and from the Pacific sector of Antarctica to the east coast of Australia. The identified seasonal distributions and migratory pathways provide valuable information to aid in monitoring the recovery of this vulnerable sub-species. We suggest the identified distribution and dispersal from the Southern Kerguelen Plateau and Dumont d’Urville sites to the west and east coasts of Australia respectively, as well as the spatial separation between Antarctic sites, provide preliminary evidence of separate sub-populations of the Southern Hemisphere sub-species of fin whale.

Diel patterns of fin whale 20 Hz acoustic presence in Eastern Antarctic waters

“…Previous work recorded a pattern of seasonal acoustic presence of fin whales in Eastern Antarctic waters with the animals present at Prydz from late January to May, at the Southern Kerguelen Plateau from February to June, at Casey from February to May and at Dumont d'Urville from February to June ( table 2 , figure 3 ) [ 25 ]. The effect of light regime on fin whale acoustic presence differed between sites in Eastern Antarctic waters.…”

“…The Casey site was the only location in the Indian sector of Antarctica to not record a diel pattern in fin whale 20 Hz acoustic presence. The lack of a diel pattern at this site was probably due to the long-term pattern of intermittent and inconsistent acoustic presence of fin whales in this region [ 25 ]. Fewer animals were vocally present and calling at this location, with Casey suggested as an area of limited use of populations of fin whale in Eastern Antarctica [ 25 ].…”

“…The lack of a diel pattern at this site was probably due to the long-term pattern of intermittent and inconsistent acoustic presence of fin whales in this region [ 25 ]. Fewer animals were vocally present and calling at this location, with Casey suggested as an area of limited use of populations of fin whale in Eastern Antarctica [ 25 ]. The increase in fin whale acoustic presence in 2019 was probably responsible for the observed diel variability in acoustic presence.…”

“…The detection of fin whale pulses at these four Antarctic sites is described in Aulich et al . [ 25 ], and the detection process is detailed in Aulich et al . [ 27 ].…”

“…Using passive acoustic monitoring, the distribution of the fin whale has been identified in Eastern Antarctic waters, with a seasonal acoustic presence of the animals from late austral summer to early winter (January–June) [ 25 ]. It is important to note that this study represents acoustic presence of the animals, and a lack of calls does not confirm an absence of fin whales, rather that there are no vocalizing animals present.…”