Encounter Bay, South Australia, an important aggregation and nursery area for the southern right whale, Eubalaena australis (Balaenidae: Cetacea)

Endangered Australian southern right whales, Eubalaena australis, are vulnerable to threats from human activities, particularly at calving aggregation areas. As the population increases, new calving areas are being established, which are important to monitor. In the Encounter Bay/Lacepede Bay region, South Australia, distribution, relative abundance, residency and site fidelity were studied using historical sightings (n = 1071, 1970-2013) and photo-identified individuals (n = 191, 2006-2019). Whales were observed throughout the study area and concentrated in Encounter Bay during April to November where an inshore core calving area was identified between Port Elliot and the River Murray Mouth. Annual maximum daily sightings increased from 2 to 8 ((X) over bar = 2.9) whales during 1983-1997 to 1-25 ((X) over tilde = 8.6) after 2002. Numbers of identified female-calf pairs (CC) increased from 10 (2006-2012) to 31 (2013-2019). During 2013-2019, when survey effort increased, a mean of 4.4 (1-9 pairs/year) CC and 18.0 (7-40/year) unaccompanied animals (UA) visited Encounter Bay each season. Mean residency was greater for CC (51.3, 13-126 days) than UA (13.4, 2-40 days). Calving females that arrived pregnant had more than twice the residency time than those first sighted with a calf. A quarter of calving females returned in two or three subsequent seasons. Encounter Bay is an important calving area and requires reclassification by the Commonwealth from "emerging aggregation area" to "small, established aggregation area". Ongoing research is needed to document southern right whale population dynamics at Encounter Bay in the context of the broader Australian population.