Southern right whales (Eubalaena australis) return to a former wintering calving ground: Fowlers Bay, South Australia

Abstract

Southern right whales (SRW), Eubalaena australis, have reoccupied historically important winter habitat ranges (calving grounds) in recent years along the southern Australian coast. Here we present findings of increased abundance of SRW at Fowlers Bay, South Australia, a previous shore‐based whaling station. This study investigates: SRW inter‐ and intraseasonal trends in relative abundance; changes to the relative proportion of the southwestern subpopulation represented by SRW at Fowlers Bay; distribution; and occupancy. Sighting and photo identification data were collected during annual aerial (1993–2016) and vessel surveys (2014–2016). The total number of female and calf pairs was 3 during 1993–2003 and 63 during 2004–2014. Despite high variability in annual relative abundance, the rate of mean increase from 1993 to 2016 (29.0%/yr, 95% CI = 0, 54.2) exceeded the maximum biological rate for the species (6%–7%/yr). Peak relative abundance was recorded in July and August. SRW at Fowlers Bay represent an increasing proportion of the southwestern subpopulation (range = 0.9%–7.4%). Mean occupancy was 23 d (range = 1–75) for female and calf pairs and 2 d (range = 1–15) for unaccompanied adults. Reduced sightings in 2015 and 2016 demonstrate plasticity in SRW abundance at Fowlers Bay. Research into the movement and connectivity of SRW is needed to understand drivers of habitat dispersal in Australia.

Calving rates, long-range movements and site fidelity of southern right whales (Eubalaena australis) in south-eastern Australia

“…There are also records of short-term use by mother-calf pairs along the Victorian, Tasmanian and southern NSW coastline from May to September (Stamation et al, 2020). On the contrary, range expansion has been reported for southern right whales in other parts of their range, including South Australia (Charlton et al, 2019b), Argentina and Brazil (Danilewicz et al, 2016;Rowntree et al, 2001;Seyboth et al, 2016) South Africa (Barendse and Best, 2014) and New Zealand (Carroll et al, 2011;Carroll et al, 2014). Sighting data collected from outside Logans Beach is primarily incidental, with sporadic aerial surveys conducted along the south-eastern Australian coastline over the last 3 decades (Kemper et al, 1997;Watson et al, 2014).…”

Population structure of North Pacific gray whales in light of trans‐Pacific movements

“…Whether colonization of new or formerly used habitats leads to additional population structure or increased homogenization presumably relates to the processes driving the range expansion. For gray whales, it seems likely that the colonization of the SI feeding ground by ENP gray whales was driven at least in part by increases in abundance decades ago following their protection, similar to patterns seen among some Southern Hemisphere right whale populations leading to reclaimed historical calving and feeding grounds as their numbers have increased in recent years (Arias et al, 2018; Carroll et al, 2014; Charlton et al, 2019; Roux et al, 2015). Although little is known about the whales feeding off Sakhalin prior to 1995, model‐based estimates of recruitment suggest that the Sakhalin feeding ground has been largely or entirely closed to immigration in recent years (Cooke et al, 2017b).…”

Southern right whale (Eubalaena australis) population demographics at major calving ground Head of Bight, South Australia, 1991–2016

“…between 1996 and 2017 for all individuals but is showing no signs of an increase in reproductive females (Stamation et al, 2020). The lower rate of increase recorded at HoB is likely to be reflective of the site being an open population with regular movement of individuals into and out of the area and the expansion into former calving grounds (Charlton et al, 2019b). Similarly, lower rates of increase were recorded for HoB compared with the overall south‐western population for 1992–2006 reported in Burnell (2008).…”

“…The abundance trend data contributes significantly to conservation management of the species nationally by informing management on the presence of SRW inside and outside of marine parks and highlighting the need to monitor and protect whales outside of the large established aggregation areas such as HoB (Charlton et al, 2019b). Whales at HoB are protected by the Marine Mammal Sanctuary Zone of the Great Australian Bight Commonwealth Marine Reserve, which provides a no‐access zone during the whale season, May–November and is the only no‐access zone providing protection for SRW in south‐western Australia.…”

“…Female SRWs are known to display a high degree of philopatry; however, coastal movements and changes in selected calving habitat also occur (Best, Brandão & Butterworth, 2001;Burnell, 2001;Cooke, Rowntree & Payne, 2001;Pirzl et al, 2009;Charlton, 2017). Shifts in selected calving habitat from HoB to Fowlers Bay were reported by Charlton et al (2019b). A shift in selected calving habitat of a known female with high site fidelity to Logans Beach, Victoria in southeastern Australia was observed and the female relocated to HoB where she then displayed site fidelity over a 9-year period (Watson et al, 2021).…”