Species group report card




старонка1/3
Дата канвертавання25.04.2016
Памер189.72 Kb.
  1   2   3
Species group report card
—cetaceans

Supporting the marine bioregional plan


for the South-west Marine Region

prepared under the Environment Protection and Biodiversity Conservation Act 1999

MAR171.0612

Disclaimer

© Commonwealth of Australia 2012

This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the Commonwealth. Requests and enquiries concerning reproduction and rights should be addressed to Department of Sustainability, Environment, Water, Population and Communities, Public Affairs, GPO Box 787 Canberra ACT 2601 or email public.affairs@environment.gov.au
Contents

Species group report card—cetaceans

1. Cetaceans of the South-west Marine Region

2. Vulnerabilities and pressures

3. Relevant protection measures



References

Attachment 1: Cetacean species occurring in the South-west Marine Region

Species group report


card—cetaceans

Supporting the marine bioregional plan for the South-west Marine Region


prepared under the Environment Protection and Biodiversity Conservation Act 1999

Report cards

The primary objective of the report cards is to provide accessible information on the conservation values found in Commonwealth marine regions. This information is maintained by the Department of Sustainability, Environment, Water, Population and Communities and is available online through the department’s website (www.environment.gov.au). A glossary of terms relevant to marine bioregional planning is located at www.environment.gov.au/marineplans.

Reflecting the categories of conservation values, there are three types of report cards:


  • species group report cards

  • marine environment report cards

  • heritage places report cards.

While the focus of these report cards is the Commonwealth marine environment, in some instances pressures and ecological processes occurring in state waters are referred to where there is connectivity between pressures and ecological processes in state and Commonwealth waters.

Species group report cards

Species group report cards are prepared for large taxonomic groups that include species identified as conservation values in a region; that is, species that are listed under Part 13 of the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and live in the Commonwealth marine area for all or part of their lifecycle. All listed threatened, migratory and marine species and all cetaceans occurring in Commonwealth waters are protected under the EPBC Act and are identified in the relevant marine bioregional plans as conservation values.

Species group report cards focus on species for which the region is important from a conservation perspective; for example, species of which a significant proportion of the population or an important life stage occurs in the region’s waters.

For these species, the report cards:



  • outline the conservation status of the species and the current state
    of knowledge about its ecology in the region

  • define biologically important areas; that is, areas where aggregations
    of individuals of a species display biologically important behaviours

  • assess the level of concern in relation to different pressures.




1. Cetaceans of the South-west Marine Region

Under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), all cetaceans (whales, dolphins and porpoises) are protected in Australian waters. Thirty-three species of cetacean protected under the EPBC Act are known to occur in the South-west Marine Region and a further nine species may occur infrequently in the region (Attachment 1).

Use of the region’s marine habitats and resources varies among cetaceans. Baleen whales occurring in the region include regular visitors such as southern right, humpback and blue whales, as well as less commonly seen species such as fin, sei and pygmy right whales. Baleen whales use the region for calving (southern right), feeding (blue whale), and as a migration pathway (including resting areas) between their feeding and breeding areas (humpback whales). Toothed whales found in the region include sperm whales, killer whales and pilot whales. They feed on a wide range of prey including fish, squid and, in the case of killer whales, other marine mammals.

Beaked whales also occur in the region. Information is limited on the ecology of beaked whales, and most information about the species group has been gleaned from stranded specimens (MacLeod & Mitchell 2006). Beaked whales are generally found in deep water offshore around seamounts and canyons. They dive for long periods and are rarely observed. South-west Australia has been listed as one of the key areas for beaked whales worldwide, particularly Hector’s, Andrew’s and Cuvier’s beaked whales (MacLeod & Mitchell 2006), while the most common beaked whale to strand in South Australia is the strap-toothed beaked whale (Kemper 2008).

This report card focuses on four species (blue, southern right, humpback and sperm whales) in the South-west Marine Region. These species are the focus of the report card as there is a relatively large amount of information on these species and the region is known to support biologically important behaviours (e.g. calving/nursing, migration, resting on migration, and foraging). While other species of cetacean feed, breed and calve in the region they are less well understood and are not discussed in this report card.

Blue whale

The taxonomy of blue whales (Balaenoptera musculus) is unclear but it is generally accepted that there are two subspecies in the Southern Hemisphere: Antarctic blue whales (B. m. intermidia) and pygmy blue whales (B. m. brevicauda). Antarctic blue whales are typically found south of 60° S and pygmy blue whales are found north of 55° S. As Antarctic blue whales feed predominantly in polar waters, and acoustic information indicates that Antarctic blue whales are likely to occur infrequently in the region, it has been suggested that the majority of blue whales sighted in Australian waters are pygmy blue whales (Branch et al. 2007). The following information is relevant to blue whales at the species level (Balaenoptera musculus), unless stated otherwise.

Antarctic blue whales are considered among the most endangered of all baleen whale populations (Clapham, Young & Brownell 1999). Branch, Matsuoka and Miyashita (2004) estimated a catastrophic decline in Antarctic blue whales due to whaling, from 239 000 individuals pre-whaling to 360 individuals by 1973. Recent estimates of Antarctic blue whale population size provide a circumpolar abundance estimate of 2280 (Branch 2008). There are no comparable data for pygmy blue whales, although they were whaled illegally after whaling bans were in place: an estimated 11 000 catches were undeclared to the International Whaling Commission (Mikhalev 2000).

Although there is not a population estimate available for pygmy blue whale in Australia, McCauley and Jenner (2010) used acoustic data to estimate abundance of the population of pygmy blue whales migrating south along the Western Australian coast. Their abundance estimate was based on acoustic data recorded in 2004 and provided an estimate of between 662 to 1559 whales.

The sighting rates of blue whales, (with the large majority probably pygmy blue whales), off southern and western Australia are among the highest recorded (Branch et al. 2007). It is likely that pygmy blue whales in the area from Tasmania west to Indonesia form one population (Branch et al. 2007). This hypothesis is supported by acoustic data, which indicates that blue whale calls from aggregations at the Bonney Upwelling (located in the South-east Marine Region) and the Perth Canyon are identical (McCauley et al. 2004). Also, by photo-identification matching, Jenner, Gill and Morrice (unpublished data) have demonstrated an interchange between the Bonney Upwelling and Perth Canyon.

The migratory habits of pygmy blue whales along the Western Australian coast are now reasonably well understood (see McCauley and Jenner 2010).On their northern migration pygmy blue whales come into the Perth Canyon in the period January to May and then head up the coast passing Exmouth in the period April through to August before continuing north, with animals known to frequent Indonesian waters. Their southern migration down the


Western Australian coast is from October to late December.

Acoustic records from off Cape Leeuwin in July–October are exclusively for Antarctic blue whales, with no pygmy blue whale call types recorded there during this time of year (McCauley et al. 2004). However, acoustic records suggest only a small number of Antarctic blue whales are likely to be present in the region.

Blue whales, principally pygmy blue whales, use the region for migration, foraging, feeding and resting. Blue whale aggregations in Australian waters appear to be determined by the location of predictable, productive feeding grounds (e.g. the Bonney Upwelling and Perth Canyon).

The Perth Canyon is a seasonally important aggregation area where pygmy blue whales feed on krill at depths of 200–300 metres in the canyon from January to May (with feeding peaking in the area from March to May). Up to 40 blue whales have been sighted in a single aerial survey in the Perth Canyon; however, numbers vary from year to year.

The Eastern Great Australian Bight Upwelling/Kangaroo Island canyons are other important foraging habitats for pygmy blue whales between November and May (peaking in December). The first aerial survey in this area (2003–04) found up to 30 blue whales feeding in the area (Gill & Morrice 2008). Aerial surveys in 2003–04, 2004–05 and 2005–06 show that blue whale relative abundance in the eastern Great Australian Bight is highly variable both between and within seasons.

Geographe Bay is thought to be an important migratory habitat for pygmy blue whale from September to December, with cows and calves observed resting in the area. Relatively high numbers of blue whales have been observed annually in Geographe Bay, during October–December surveys, since 1994. Surveys in 2003 recorded more than 100 sightings (Burton 2003). No feeding behaviour has been observed in Geographe Bay; however, small calves are regularly seen. Most whales move slowly into the bay from the north and follow the shallow bathymetry around Cape Naturaliste to the west.



Southern right whale

In 1997, the International Whaling Commission (2001) estimated that 17 per cent, or approximately 1200, of the global southern right whale (Eubalaena australis) population occurred in Australia (based on a global abundance of 7 000). Currently, the southern right whale population is increasing at or close to the maximum biological rate. The total current Australian population is approximately 2 400 individuals (Bannister 2009).

Shore-based and pelagic whaling in the early to mid-1800s reduced the southern right whale population off Australia to a remnant population. Low-level catches continued until at least the 1930s, principally in pelagic whaling operations. A take of 3 368 southern right whales by the former Soviet Union in the period 1950–71 (Tormosov et al. 1998; Yablokov 1994), despite international protection, is likely to have prevented significant recovery until more recent decades. The recovery of the species is not yet assured as the current population is likely to be less than 10 per cent of pre-exploitation abundance (IWC 2001). In addition, recovery in severely and rapidly depleted populations is likely to be affected by a loss of genetic diversity, making the species more vulnerable, for example, to a random disease event (IWC 2001).

Southern right whales migrate from their summer feeding grounds in the Southern Ocean to calve and breed in warmer coastal waters. Southern right whales are seasonally present off the Australian coast between about May to November, and have been recorded in the coastal waters of all Australian states except the Northern Territory (Bannister, Kemper & Warneke 1996). The entire coastline from Kangaroo Island westward and south of the Perth Canyon is thought to be an important migratory pathway for the southern right whale. Principally they are found aggregating adjacent to the region, in state waters around the southern coastline off southern Western Australia and far west South Australia.

The main calving areas adjacent to the South-west Marine Region (based on observations of mothers with very young calves in multiple years) currently known for southern right whales include:


  • Western Australia—Doubtful Island Bay (including the Point Ann to Point Charles area), Israelite Bay area, Twilight Cove, Flinders Bay, Albany to Cape Riche area and Yokinup Bay to Cape Arid area

  • South Australia—Head of Bight, Fowlers Bay and Encounter Bay (DEH 2005a).

Southern right whales exhibit a strong tendency to return to the same breeding location (Bannister 1990; Burnell 1999; Payne 1986). This is particularly evident for reproductively mature females: Burnell (1999) reported that 92 per cent of reproductively mature females showed a tendency to return to the Head of Bight calving area. Approximately 85 per cent of calves born at the Head of Bight also exhibited fidelity to their birthing location (Burnell 1999). Individuals make long-distance coastwise movements within a breeding season (Burnell 2001; Burnell & McKenna 1996), and movement of reproductively mature females between the breeding grounds has been recorded (Australian Marine Mammal Centre 2009). While southern right whales can be considered a highly mobile species, the tendency for individuals to return to the same location may limit or delay dispersal.

Humpback whale

Humpback whales (Megaptera novaeangliae) were heavily exploited through commercial whaling in all areas where they are known to have been abundant. The exact figure of how many whales were killed is uncertain (Baker & Clapham 2004; Yablokov 1994). It is thought that 95 per cent of the overall population was eliminated (Johnson & Wolman 1985).

It is generally recognised that the Australian populations appear to be growing consistently at about 10 per cent per year (Bannister & Hedley 2001; Bryden, Kirkwood & Slade 1990; Chaloupka & Osmond 1999; Paterson, Paterson & Cato 2001, 2004). Current estimates for the Australian west coast population is currently estimated to be 21 750 (Hedley, Bannister & Dunlop 2009).

Humpback whales migrate annually between their summer feeding grounds in Antarctica to their tropical and subtropical breeding grounds in winter. During migration, individuals travel alone or in temporary aggregations of generally non-related individuals (cow–calf pairs being the exception) (Valsecchi et al. 2002). The exact timing of the migration period can vary from year to year depending on water temperature, sea ice, predation risk, prey abundance and the location of the feeding ground (DEH 2005b). In general, humpback whales are sighted in southern Australian waters in May and migrate slowly up the east and west coasts. By October, most whales have started their southward migration and sightings are rarer after November.

Humpback whales migrate through coastal areas between Esperance and Kalbarri. Along parts of their migratory route there are narrow corridors and bottlenecks resulting from physical barriers where the majority of the population passes close to shore (that is within 30 kilometres of the coastline) (DEH 2005b). In the South-west Marine Region such narrow migratory corridors appear to be found in the following three areas:


  • waters between the Houtman Abrolhos Islands and the coast near Geraldton

  • waters from Geographe Bay to Rottnest Island

  • waters to the east of Augusta.

Resting areas are used by cow-calf pairs and attendant males during the southern migration. Sheltered bays appear to be opportunistically used for this purpose. There is some debate amongst scientists about resting areas for the species in the South-west Marine Region, as typically the species is observed resting in protected, shallow coastal waters. However, Geographe Bay is considered to be a resting area for the species.

Recent satellite tracking data collected by the Australian Marine Mammal Centre, however, also indicates that some humpback whales on the west coast of Australia migrate well offshore.



Sperm whale

Assessments of sperm whale (Physeter macrocephalus) abundance have historically been based on the analysis of whaling data. More recently, surveys have been done in 24 per cent of the sperm whales’ global habitat and have produced population estimates of 300 000–450 000 (Whitehead 2002). Although these estimates are based on extrapolating surveyed areas to non-surveyed areas, without a systematic survey design, these are probably the best available and most current estimates of global sperm whale abundance (National Marine Fisheries Service 2006).

In contrast, an estimate of the pre-whaling (1712) sperm whale population size is approximately 1 267 000 individuals (Whitehead 2002). This suggests that the current population is about 32 per cent of the pre-whaling level and is therefore considerably depleted. The greatest sperm whale catches have occurred since the ‘modern’ era of whaling with engine-powered whaling vessels, harpoon guns and other technical aids, but have almost ceased since the 1986 International Whaling Commission moratorium on commercial whaling. Despite the high level of take (approximately 900 000), the sperm whale remains the most abundant of the large whale species. Given that current and potential threats to the sperm whale are limited, it is likely that the global population of sperm whales is increasing.

Sperm whales tend to inhabit offshore areas with a water depth of 600 m or more, and are uncommon in waters less than 300 m deep (NOAA 2006). Female sperm whales are generally found in deep waters (at least 1 000 m). Female and young male sperm whales appear to be restricted to warmer waters north of about 45° S in the Southern Hemisphere, while adult males travel to and from colder waters of Antarctica (Bannister, Kemper & Warneke 1996). Immature males will stay with females in tropical and subtropical waters until they begin to slowly migrate towards the poles, at anywhere between the ages of 4 and 21 years old.

Concentrations of sperm whales are found where the seabed rises steeply from great depth, and are probably associated with concentrations of major food in areas of upwelling (Bannister, Kemper & Warneke 1996). In the South-west Marine Region, it is thought the species is likely to forage along the shelf-break. Sperm whales seem to be concentrated in a narrow area only a few miles wide at the shelf edge off Albany, Western Australia, moving westwards through the year (Bannister, Kemper & Warneke 1996). They have been observed foraging in waters over the Perth Canyon and over the Albany canyons group. Sperm whales are also known to occur in waters along the shelf break of the eastern Great Australian Bight, and waters to the south of Kangaroo Island, and are presumed to be foraging in these areas. Bremer Canyon is a place where sperm whales and killer whales are known to aggregate (Riggs, 2011)

Biologically important areas

Biologically important areas (BIAs) are areas are areas that are particularly important for the conservation of the protected species and where aggregations of individuals display biologically important behaviour such as breeding, foraging, resting or migration. The presence of the observed behaviour is assumed to indicate that the habitat required for the behaviour is also present. Biologically important areas have been identified for some EPBC Act listed species found in the South-west Marine Region, using expert scientific knowledge about species’ distribution, abundance and behaviour in the region. The selection of species was informed by the availability of scientific information, the conservation status of listed species and the importance of the region for the species. The range of species for which biologically important areas are identified will continue to expand as reliable spatial and scientific information becomes available.

Based on available information, biologically important areas have been identified for the blue whale, southern right whale, humpback whale and sperm whale. Behaviours that have been used to define these for cetaceans include aggregating, resting, foraging, migrating, breeding and calving (Table 1). Biologically important areas are included in the South-west Marine Region Conservation Values Atlas (www.environment.gov.au/cva).

Table 1. Cetaceans for which biologically important areas have been defined in the South-west Marine Region

Species

Conservation status

Behaviour

Pygmy blue whale
(Balaenoptera musculus)

Endangered, migratory, cetacean

Foraging, migrating, resting

Southern right whale
(Eubalaena australis)

Endangered, migratory, cetacean

Aggregating, migrating, calving

Humpback whale
(Megaptera novaeangliae)

Vulnerable, migratory, cetacean

Resting, migrating

Sperm whale
(Physeter macrocephalus)

Migratory, cetacean

Foraging

2. Vulnerabilities and pressures

Vulnerabilities

During the early 1800s, whaling was an important industry in the region. Semi-permanent camps were set up on Eyre Peninsula, Kangaroo Island, the Esperance area of Western Australia and as far north as Shark Bay, to target a range of the larger species. Overexploitation and dramatic declines in whale numbers eventually led to the demise of the industry. Australia’s last whaling station, at Cheynes Beach near Albany, closed in 1978. In 1979, Australia adopted a pro-conservation policy, putting a permanent end to whaling in Australian waters.

Although a global moratorium on commercial whaling has been in place since 1986, populations of all species are still below pre-whaling estimates—most are considerably so. Two populations of targeted species have been recovering—the southern right whale and the west coast population of the humpback whale are increasing at rates close to their biological capacities. While not a current threat to most species, whaling is still listed as the most threatening anthropogenic activity in all five threatened cetacean recovery plans under the EPBC Act.

The life history characteristics of cetaceans make them susceptible to a range of pressures in the marine environment. They are long-lived animals that are generally slow to reach sexual maturity and have low fecundity (e.g. only producing one calf at a time and not necessarily calving every year). For example, female southern right whales do not reach sexual maturity until five or six years of age and generally have one calf at three-year intervals. In addition to these traits, many species travel relatively long distances to reach resting, foraging and breeding areas. Consequently, cetaceans are considered susceptible to anthropogenic impacts, as evidenced by the devastating impact that past commercial whaling had on populations of cetaceans in the region.


  1   2   3


База данных защищена авторским правом ©shkola.of.by 2016
звярнуцца да адміністрацыі

    Галоўная старонка