|Scientific Name:||Neophoca cinerea|
|Species Authority:||(Péron, 1816)|
|Taxonomic Notes:||The taxonomy of Phocarctos of New Zealand and Neophoca of Australia was confused until 1960 (Rice 1998).|
|Red List Category & Criteria:||Endangered A2bd+3d ver 3.1|
|Assessor/s:||Goldsworthy, S. & Gales, N. (IUCN SSC Pinniped Specialist Group)|
|Reviewer/s:||Kovacs, K. & Lowry, L. (Pinniped Red List Authority)|
The Australian Sea Lion has a small, genetically fragmented population. The global population is relatively small, population decline is documented at some colonies and most major colonies are at risk of extinction from fishery by-catch. This species should be classified as Endangered (EN).
IUCN Evaluation of the Australian Sea Lion, Neophoca cinerea
Prepared by the Pinniped Specialist Group
A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.
Australian Sea Lions have a non-annual and asynchronous breeding system. The mean interval between successive breeding seasons is 17.5 months (range16.0-19.9). Subpopulations across the range of the species breed at different times. Populations as near as 20 km can be up to 6 months out of phase in the timing of breeding. There are 73 known breeding sites. 61 of these produce >5 pups, with a total breeding cycle pup production estimated at 3,455 (mean pup production 57, median 27). 80% of the population is located in South Australia, 20% in Western Australia. Based on an age-structured model, the number of mature animals in the population is ~6,600 (Females >4.5 years; males >6 years). Genetic population substructure in the species is extreme, with most colonies (subpopulations) having unique mtDNA lineages, demonstrating extreme philopatry and meeting the IUCN definition of a severely fragmented population.
Some age-structure data are available for one Australian Sea Lion population (Seal Bay, Kangaroo Island). The generation time has been estimated to be 12.4-12.8 years. Hence 3 generations is equivalent to ~38 years.
Robust data on trends in abundance (based on pup abundance per breeding season) are available for only the three largest subpopulations:
- Seal Bay (Kangaroo Island)- pup abundance estimates have declined by 12.6% over 13 breeding season (17.7 years), a decline of -0.77%/year (-1.14%/breeding season), and population modeling projects the subpopulation to decline ?50% within 3 generations 38 years.
- The Pages Islands - trends in pup abundance for 13 breeding seasons show no significant change (i.e. stable).
- Dangerous Reef- trends in pup abundance over 8 breeding seasons from 1994/95 to 2006/07 indicate an increase of 6.9%/breeding season (4.6%/year). Most of this increase has taken place since 2000.
The main threat to the Australian Sea Lion is bycatch in demersal gillnet and trap fisheries. The recovery of the Dangerous Reef population coincides with closures in the gillnet fishery in Spencer Gulf in 2000. Fishery closures also provide protection for most of the foraging space of The Pages Islands subpopulation (stable). There are no substantive gillnet fishery closures that provide protection for the foraging space of the Seal Bay subpopulation which is declining.
No accurate trend data are available for the majority of subpopulations with low pup production (>70% of populations produce <50 pups).
Historical reductions in range and population size from sealing (1800-1830) and subsequent take are inferred. Recent reductions (last 30-40 years) have been inferred or suspected from the high proportion of small and potentially declining subpopulations based on actual and potential levels of bycatch in gillnet and trap fisheries. The causes of reduction and threat are reversible and understood (but have not ceased); thus, this criterion is not applicable.
A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on any of (a) to (e) under A1.
Declines have been detected at Seal Bay (12.6% decline over 13 breeding seasons, equivalent to a 25% decline over 3 generations). A population model suggests that this population will continue to decline at a level that will be ?50% within 3 generations.
The high proportion of small subpopulations in the species (50% produce ?27 pups per breeding season) is thought to be a consequence of systemic declines that have resulted from sustained fisheries by-catch over the last 40 years. However, trend data for these small populations are of poor quality or are totally lacking.
The major causes for reduction based on observed and potential levels of by-catch in gillnet and trap fisheries are known and have not ceased. As the rate of decline has only been estimated for one subpopulation and ranges from 25 to ?50% reduction over 3 generations, and declines are inferred in other (depleted) subpopulations, the Australian Sea Lion meets criterion A2b and A2d for Vulnerable (VU).
A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.
A population model suggests that the Seal Bay subpopulation will decline ?50% within 3 generations 38 years (indicating E). A population viability analysis indicates that many South Australian subpopulations (~30%) are vulnerable to extinction in the absence of additional by-catch mortality. With low levels of fishery by-catch mortality (egg. 1-2 additional female mortalities/year/subpopulation), 80% of subpopulations are projected to be declining, and 42% may be quasi-extinct (?10 females) within 25 years (<3 generations). Current estimated by-catch levels are likely to be within these ranges.
At a subpopulation level, under criterion A3d, 38% of South Australian subpopulations are assessed as either VU or EN, and at least 42% are assessed as Critically Endangered (CR) based on criterion A3 (d) CR if current by-catch levels remain.
A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.
A population decline has been detected in the recent past at Seal Bay (12.6% decline over 13 breeding seasons, equivalent to a 25% decline over 3 generations) and is projected to continue (?50% decline within 3 generations). The only subpopulation known to be increasing has only done so since gillnet fisheries were closed within its foraging grounds in 2000. The high proportion of small subpopulations in the species is suspected to result from systemic declines that have resulted from fisheries bycatch. Current rates of by-catch are high and have not ceased, and population modeling of South Australian populations suggests that even low levels of by-catch will lead to quasi-extinctions of some subpopulations (42% quasi-extinct within 3 generations) and continuing declines in others (38%). Hence, subpopulations range from VU to CR under A3 and A4d, though it is not possible to make an accurate global assessment for the species with available data.
B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1. Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²
EOO for Australian Sea Lions is > 20,000 km²
B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²
AOO for Australian Sea Lions is > 2,000 km²
AND at least 2 of the following:
(a) Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.
None of the criteria (a), (b) or (c) is satisfied.
C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000
Based on an age-structured model and estimates of pup production for the species, the number of mature individuals is estimated to be ~6,600 (Females >4.5 years; males >6 years). This meets criterion C for Vulnerable (VU).
AND either C1 or C2:
C1. An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
For the Seal Bay subpopulation a continuing decline is projected for the future (?50% decline within 3 generations) satisfying V. For subpopulations vulnerable to fisheries by-catch, with by-catch of ?1-2 females per year, declines are expected that would satisfy the EN or VU criteria for many subpopulations, and CR to quasi-extinct for some others.
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
For the 61 subpopulations that produce ?5 pups per breeding season, based on the number of mature individuals, most (48%) are categorized as CR , 39% as EN and 13% VU. The median number of mature individuals in each subpopulation is 52. If the breeding sites that producer <5 pups per breeding season are included, the median number of mature individuals per subpopulation would be <50, which satisfies a classification of CR.
(a ii) % individuals in one subpopulation: CR = 90?100%; EN = 95?100%; VU = 100%
The largest subpopulation contains ~20% of individuals of the species.
(b) Extreme fluctuations in the number of mature individuals.
Based on C, C1 and C2(ai), the species is categorized as VU, although under some criteria, EN and CR could be justified.
D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5
The number of mature individuals in the Australian Sea Lion population is estimated to be ~6,600. This does not meet any of the above criteria.
E. Quantitative analysis
Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years
A population viability analysis has been undertaken for South Australian subpopulations (assuming a stable population structure, r = 0). PVAs were undertaken on individual subpopulation because of the extreme philopatry in the species. These determined that with no additional bycatch mortality, ~30% of subpopulations are presently categorized as EN or CR, based on criterion E. With low levels of fishery by-catch mortality (e.g., 1-2 additional female mortalities/year/subpopulation), 80% of subpopulations are categorized as either EN or CR, with 42% quasi-extinct (?10 females) within 25 years. Current estimated bycatch levels are likely to be within these ranges. Based on these quantitative analyses, at least 42% of South Australian populations would meet the criterion for Critically Endangered (CR), and 38% meet the criterion of either Endangered (EN) or Critically Endangered (CR).
Listing recommendation ? The Australian Sea Lion population is thought to be significantly reduced in size from historical levels. It is a non-annual, asynchronous breeder that exhibits extreme site fidelity to its multiple, small colonies within its fragmented population. Based on: levels of fishing effort over the last 40 years; current estimates of fishery by-catch rates of sea lions; the high proportion of small, depleted subpopulations; quantitative analyses, which suggest that until fishery by-catch is manage, subpopulations will continue to decline or disappear; and projected declines in abundance in excess of 50% for major colonies - the Australian Sea Lion should be classified as Endangered (EN).
|Range Description:||Australian Sea Lions are found in southern and southwestern Australia from just east of Kangaroo Island west to Houtman Albrolhos in Western Australia. Vagrants have come ashore in Eastern Australia, as far north as the middle of New South Wales. Australian Sea Lions breed on at least 73 islands and at several mainland sites (McKenzie et al. 2005). Five sites account for approximately 60% of the annual pup production.|
|FAO Marine Fishing Areas:||
Indian Ocean – eastern
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The total population of Australian Sea Lions is estimated to be 13,790 individuals based on an estimated total pup production of 3,380 (2,674 in South Australia and 706 in Western Australia) and a multiplication factor of 4.08 pups per breeding cycle (Goldsworthy et al. 2003, Goldsworthy and Page 2007).|
|Habitat and Ecology:||
Australian Sea Lions are sexually dimorphic, with adult males reaching 1.25 times the length and 2.5-3.5 times the weight of adult females. Very little information on sizes of adult males is available, and some values in the literature may be overestimates. Adult males reach lengths of at least 2.5 m and weights of 200 to at least 300 kg. Females are 1.3 to just over 1.8 m and weigh from 61-105 kg. At birth, pups are approximately 60-70 cm long and weigh 6.4-7.9 kg. Pups are dark chocolate brown to charcoal in colour at birth and lighten to a smoky gray. The crown is paler than the rest of the body and there is a dark mask across the face. The postnatal moult starts when pups are 8-10 weeks old and is completed in several weeks; pups in their juvenile pelage resemble adult females.
Females become sexually mature at 4.5-6 years of age and males at 6 years or more. The mean age of breeding females is 11 years (McIntosh 2007). The oldest breeding female recorded was aged 24 years, while the maximum longevity recorded is 26 years for females and 21.5 years for males (McIntosh 2007). Age-specific survival probabilities are high (0.98) after six years of age and are similar for males and females (McIntosh 2007).
Australian Sea Lions are unusual among pinnipeds in having a supra-annual pupping interval (Gales et al. 1994, Gales and Costa 1997), with females producing pups every 17-18 months (mean breeding interval is 17.5 months, range 16.0-19.9). Females mated about 7-10 following the birth of a pups. Like most other pinnipeds, there is a 4-6 month period of delayed implantation of the blastocyst following conception. This leads to a prolonged (active) placental gestation of up to 14 months, the longest for any pinniped (Gales and Costa 1997). The annual pregnancy rate of mature females is ~71 % (Higgins and Gas 1993). Pups can be born at any time of the year, with females at a given site being loosely synchronous with each other and pupping generally occurring over a 5-7 month period at a given locale (Higgins 1993). Even neighbouring sites can be on entirely different breeding schedules. Males are sequentially polygynous, establishing territories around individual females, herding them in an effort to keep them from departing until the onset of estrous. This pattern is repeated until the male is compelled to go to sea and forage, after which he returns and repeats the strategy. Males defend their territories with guttural clicking, growling and barking vocalizations, posturing, and by fighting with rivals. Pups can be trampled when males are fighting or moving rapidly to confront rivals and control females, and killed outright in aggressive acts.
Pups are continuously attended for the first 9-10 days after birth. Over the next 5 months females make foraging trips that average 48.5 hours in length, followed by pup attendance periods that average 33 hours. Females suckle their pups for 15-18 months, usually weaning them a month before giving birth again. Some females care for their offspring for up to three years, and can be seen with a juvenile and a new pup. Adult female Australian Sea Lions behave aggressively toward pups that are not their own. Pups will play at the shoreline and in tide pools while their mothers are away, and following their postnatal moult, will actively swim on their own.
Adult female Australian Sea Lions are benthic, diurnal foragers (Costa and Gales 2003). They routinely transit to foraging locations by swimming along the bottom. Mean depth of dives from a series of lactating females tagged with time depth recorders ranged from 41.5-83.1 m; maximum depth of dives ranged from 60-105 m. Mean duration of dives ranged from 2.2-4.1 minutes, and the longest dive recorded lasted 8.3 minutes. Australian sea lions are fast, powerful swimmers and often ?porpoise? out of the water when moving rapidly at the surface.
These sea lions are considered non-migratory and probably spend most of their lives near their natal colony. The greatest distance travelled by a tagged animal is approximately 250 km. Genetic distinctiveness has been reported between nearby colonies, indicating a high degree of site fidelity and female philopatry (Campbell et al. 2008). At sea, Australian Sea Lions spend nearly all of their time in waters over the continental shelf.
Australian Sea Lions are thought to concentrate their efforts on shallow-water benthic prey, but also take a wide variety of fishes, such as rays, small sharks, Australian salmon, and whiting. Other prey includes squid, cuttlefish, small crabs, and occasionally (perhaps rarely) penguins, flying seabirds and small sea turtles. Fishermen complain of sea lions robbing lobster traps and fishing nets. Large prey items may be taken to the surface and shaken into portions that can be swallowed.
Predators include Great White Sharks (Shaughnessy et al. 2007) and presumably Killer Whales (Ling 2002).
Australian aborigines have taken Australian Sea Lions for subsistence purposes for thousands of years. Early European colonists also took sea lions for food and other products, although numbers recorded in sealing logbooks were small (Ling 1999). Harvests by sealers in the 17th and 18th centuries reduced the population and extirpated them from areas around the Bass Strait and Tasmania.
Although now protected, the population has not rebounded fully in numbers or reoccupied all of its former range. Conflicts and interactions with fisheries exist. A high level of entanglement in abandoned and lost fishing gear and in marine debris has been reported, with a range of 0.2 to 1.3% of the population are entangled in these materials (Shaughnessy et al. 2003, Page et al. 2004). Other animals become entangled in fishing gear, particularly bottom-set gillnets of commercial shark fishers. A risk assessment of sea lion by-catch in shark gillnets indicated that there is a high risk of subpopulation extinction with even low levels of by-catch (Goldsworthy and Page 2007). A substantial sea lion tourist industry has developed; this activity is regulated at sea lion colonies in parks to minimize disturbance during the breeding season. Extensive disturbance can cause Australian Sea Lions to abandon colony sites.
|Conservation Actions:||This species is protected in Australia by State Conservation agencies under numerous independently enacted state laws, the earliest dating back to 1889. The Environment Protection and Biodiversity Conservation Act of 1999 provides protection for all pinnipeds in Australia. The Australian Sea Lion was listed as a Threatened species in the Vulnerable category in 2005. In South Australia, it was listed in February 2008 as Vulnerable under the National Parks and Wildlife Act of 1972. Fisheries are regularly monitored for evidence of marine mammal by-catch (Shaughnessy 1999). Australian fisheries have also attempted to reduce marine mammal by-catch through the development of several action plans and the development of a code of conduct for responsible fishing for at least one fishery. Several NGOs monitor by-catch issues and have prepared publications on ways to reduce marine mammal mortality in Australia?s fisheries (see Shaughnessy et al. 2003).|
|Citation:||Goldsworthy, S. & Gales, N. (IUCN SSC Pinniped Specialist Group) 2008. Neophoca cinerea. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 13 December 2013.|
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