Geographe Bay to Eucla Shelf and Coastal Waters IMMA

Criterion A – Species or Population Vulnerability

Blue whales are listed as Endangered globally (IUCN 2020) and in Western Australia (WA) (Biodiversity Conservation Act, 2016). The total eastern Indian Ocean blue whale population last estimated in 2010 was small at 662-1559 (McCauley & Jenner 2010) and is presumably still recovering from commercial whaling. Australian sea lions are Globally listed as Endangered (IUCN 2020) and Vulnerable within WA (Biodiversity Conservation Act 2016). The species is endemic to Australia, occurring only in WA and South Australia. Some breeding island sub-populations are in decline, and none are increasing (Friedman and Campbell 2014).

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations 

Sheltered, coastal waters of the area, stretching from Geographe Bay (most westerly area), to Israelite Bay (most easterly area) contain important calving grounds for southern right whales; a species having high calving ground site fidelity with mothers returning to calve at the same locations. Large established aggregation areas are recognized (according to the Commonwealth criteria) at Doubtful Island and Israelite Bays, while a small established area is recognized at Yokinup Bay (DSEWPaC 2012). Twilight Cove, Hassel Beach, Cheyne, Wray, Dillon and Bremer Bays are recognized as emerging coastal aggregation areas. While not yet recognised in Commonwealth aggregation area criteria, Point Charles Bay (from Point Anne to Point Charles), Cheynes Beach, King George Sound, and Geographe Bay are regularly used by southern right whales for calving and by resting mothers nursing young calves (Bannister 2001, Salgado et al. 2022). The broad coastal area within this IMMA is important as part of the network of critical calving grounds for the population. In particular, the zone from the coast up to ~2-3 km from shore along the entire southern coast of Australia is important for coastal movement corridors for southern right whales. Movement of calving and non-calving adults has been recorded across broad distances both within and across seasons (Pirzl et al. 2009).

The total eastern Indian Ocean blue whale population was estimated at 662-1559 in 2010 (McCauley & Jenner, 2010). Large numbers of pygmy blue whales from this population” (and probably some Antarctic blue whales) with calves use Geographe Bay and the Naturaliste Plateau as a narrow transit corridor (Recalde-Salas 2014; Salgado Kent et al. 2012; Salgado Kent et al. 2014). Because of this narrowing of the corridor and the relatively large number of whales using it, the area is judged as one where ‘aggregation’ occurs. Southbound blue whales move slowly into Geographe bay following the shallow bathymetry, often travelling within 100 m of the shore. In recent years shore-based day-time counts have recorded up to ~250 blue whales (Burton, unpublished data). Peak numbers are observed October-December. Flinders Bay and the Naturaliste Plateau and westward are also used by northward migrating blue whales between ~March-May (Gavrilov et al. 2012). During their northward migration, humpback whales also occur in higher densities in Geographe Bay and offshore, and within sheltered areas on the southwest coast such as Flinders Bay and King George Sound. On their southward migration, humpbacks often rest and nurse their calves and socialize in large, competitive groups. Peak numbers are observed September-November, with ~4700 humpback whales counted migrating through Geographe Bay in a season during day-time shore-based counts (Burton, unpublished data). Because of this narrowing of the corridor, namely for southbound mothers and calves, ‘the area is judged as one where ‘aggregation’ occurs. Flinders Bay and bays on the southwest coast are used by northward migrating humpback whales between ~June-August.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Australian sea lions are endemic to Australia, occurring only in Western Australia and South Australia and have experienced a greater than 60% decline over the past 40 years (Goldsworthy et al. 2021). It is unique in having large numbers of small breeding colonies, low reproductive rates, an unusually long and asynchronous breeding cycle (17-18 months), high site fidelity, and poor dispersal (Campbell et al. 2008 Lowther et al. 2012). This IMMA includes the majority of breeding islands in Western Australia, representing around 30% of the breeding sites (Goldsworthy et al.  2014; Shaughnessy et al. 2005). The high degree of site fidelity exhibited by females means that each breeding colony has become somewhat genetically isolated, making this species highly vulnerable to local extinction of breeding colonies (Campbell et al. 2008).

New Zealand fur seals breed on offshore islands between southern Western Australia and New Zealand and some Subantarctic islands (Shaughnessy 1999). During recent decades, New Zealand fur seals have been experiencing a healthy recovery from sealing. In Australia, while there is genetic exchange between the populations in WA and the east coast, colonies are separated by the Great Australian Bight (>750 km; Berry et al. 2012). In Western Australia, all 20 of the known breeding colonies are located within the IMMA (Campbell et al. 2014), and were estimated to make up 14% of the population size in Australia during the 2010 – 2014 time period (Shaughnessy et al. 2015).

Important calving grounds for southern right whales; a species having high calving ground site fidelity with mothers returning to calve at the same locations, are located within the sheltered, coastal waters of the IMMA, stretching from Geographe Bay (most westerly area) to Israelite Bay (most easterly area)  (Bannister 2001).

Sub-criterion C2: Feeding Areas

In Western Australia, all 20 of the known breeding colonies of New Zealand fur seal (Campbell et al. 2014) estimated to make up 14% of the population size in Australia during 2010 – 2014 (Shaughnessy et al. 2015) are within the IMMA. The area includes waters from the coast out to the edge of the continental shelf occupied by fur seals during foraging trips from their haul-out and breeding colonies, acting as central place foragers (Kirkwood and Goldsworthy 2013). While some New Zealand fur seals likely forage further offshore than other animals in the population, the exact extent of such foraging movements in the region is presently unknown.

Sub-criterion C3: Migration Routes

Pygmy blue whales use offshore and coastal waters of the south coast as part of a transit corridor during migration westward from the Bonney Upwelling foraging area to the Perth Canyon foraging area between February to June. More specifically, satellite tracking data from pygmy blue whales tagged off Western Australia (Double et al. 2014; Owen et al. 2016) and in the Bonney Upwelling (Möller and Attard, 2015) off South Australia have identified the area from near King Island in southeast Australia up to the Banda and Molucca Seas as the migratory pathway of pygmy blue whales.  In addition, the movement of Southern right whales between coastal aggregation areas within and across seasons, shows that the corridor between the aggregation areas is important connective habitat.  Results from a study at the Head of Bight off South Australia support the view that greater southern right whale abundance promotes increased linkage via connective corridors between aggregation areas (Charlton et al. 2019b). Within and between season movements of southern right whales on the southern Australian coastline were documented further east by Burnell (2001). While studies on SRWs in the southwest of Australia are limited, within year movements of the same sub-population on the south coast of Australia averaged 730 km, over 34 days. The maximum reported within season movement of an individual SRWs across coastal southern Australia is 1,490 km (Burnell 2001). During migration, along the west coast of the region humpback whales occur in high densities in Geographe Bay, and within sheltered areas on the southwest coast such as Flinders Bay and King George Sound. Peak numbers are observed September-November, with ~4700 humpback whales counted migrating south through Geographe Bay in a season during day-time shore-based counts (Burton, unpublished data). This area is considered the last sheltered area they rest in during their migration from low latitude breeding grounds to high latitude feeding grounds (Salgado Kent et al. 2014). Flinders Bay, King George Sound, and coastal areas along the southwest coast are used by northward migrating humpback whales between mostly from June-August. Flinders and King George Sound are areas of whale watching operations with these and southern right whales as focal species. For example, encounters by one tour vessel in King George Sound in 2012 included a total of 419 whales in 90 groups, 11 of which had calves in them. Of the groups, 84 were humpback whales, 9 of which had calves in them. Six were southern right whales, two of which had calves in them (Salgado Kent, unpublished; data provided by “Sail-A-Way” in 2012).