Australian And New Zealand Fur Seals At The Skerries, Victoria: Recovery Of A Breeding Colony

2002 ◽  
Vol 24 (1) ◽  
pp. 57 ◽  
Author(s):  
CL Littnan ◽  
AT Mitchell
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Arithmetic Mean ◽  
Aerial Photographs ◽  
Population Estimates ◽  
Breeding Colony ◽  
Mark Recapture ◽  
Aerial Surveys ◽  
Fur Seals ◽  
Breeding Seasons

The population size of Australian fur seals Arctocephalus pusillus doriferus and New Zealand fur seals A. forsteri at The Skerries, Victoria was estimated in two consecutive breeding seasons, 1999-2000 and 2000-2001 using both mark-recapture procedures and aerial surveys. 675 and 746 A. p. doriferus pups and 37 and 47 A. forsteri pups were captured and marked in 1999-2000 and 2000-2001, respectively. Resights (1999-2000 N = 3; 2000-2001 N = 6) were conducted 2 - 3 days after marking and pup population estimates were calculated using a modified Lincoln-Petersen estimate. The arithmetic mean for A. p. doriferus pup abundance was 1,867 in the first season and 2,237 in the second. A. forsteri abundance was 75 and 78, respectively. The A. p. doriferus population is estimated to have increased an average of 19.7% (r = 0.18) between 1999 and 2000. The arithmetic mean from five counts of aerial photographs of total animals present at the colony was 1,758 in 1999-2000 and 2,965 in 2000-2001. Due to high variation between counts, aerial surveys proved to be an inconsistent and inaccurate method for estimating the population of fur seals at The Skerries.

Australian fur seals at Seal Rocks, Victoria: pup abundance by mark - recapture estimation shows continued increase

2000 ◽  
Vol 27 (6) ◽  
pp. 629 ◽  
Author(s):  
P. D. Shaughnessy ◽  
S. K. Troy ◽  
R. Kirkwood ◽  
A. O. Nicholls
Keyword(s):  
Confidence Intervals ◽  
Arithmetic Mean ◽  
Rapid Rate ◽  
Exponential Rate ◽  
Guard Hair ◽  
Mark Recapture ◽  
Fur Seals ◽  
Fur Seal ◽  
Rate Of Increase ◽  
Breeding Seasons

The abundance of Australian fur seal pups was determined at Seal Rocks, Westernport, Victoria in late December 1997 using a mark–recapture procedure with repeated recapture sessions. Pups (n = 1291) were marked by clipping the black guard hair on the head to reveal lighter underfur. Recaptures from the whole colony were made on eight occasions 1–3 days later. In the recapture sessions, a mean of 32% of sighted pups had been marked. Estimates of pup numbers over the eight recapture sessions were calculated using the Petersen estimate and then combined by taking their arithmetic mean. The combined estimate was 4024 (95% confidence range 3908–4141). In 1991–92, a similar procedure led to an estimate of pup numbers of 2817 (95% confidence range 2703–2930). For both breeding seasons, estimates of pup numbers from each recapture session were also combined assuming a joint hypergeometric distribution; there was little difference in the results from the two procedures, although the confidence intervals for the hypergeometric mean were smaller than those for the arithmetic mean. From 1991–92 to 1997–98, pup numbers increased by 43%, at an exponential rate of 0.059 (95% confidence range 0.0526–0.0664), equivalent to 6.1% per annum (5.4–6.9%). This is greater than the rate of increase of pups at the colony between 1968–69 and 1991–92, which was 0.023 (95% confidence range 0.0198–0.0268), equivalent to 2.4% per annum (2.0–2.7%). Because of the rapid rate of increase of the Australian fur seal colony at Seal Rocks and the importance of the locality for tourism, we recommend that the abundance of pups there be determined every 3–5 years using a mark–recapture technique.

Changes in the abundance of New Zealand fur seals, Arctocephalus forsteri, on Kangaroo Island, South Australia

1995 ◽  
Vol 22 (2) ◽  
pp. 201 ◽  
Author(s):  
PD Shaughnessy ◽  
SD Goldsworthy ◽  
JA Libke
Keyword(s):  
New Zealand ◽  
South Australia ◽  
Early Years ◽  
Mark Recapture ◽  
Fur Seals ◽  
Fur Seal ◽  
Rate Of Increase ◽  
New Zealand Fur Seal ◽  
Breeding Seasons ◽  
Made In

Kangaroo Island was an important seal-harvesting site during the early years of European colonisation of Australia. A recent survey of the New Zealand fur seal, Arctocephalus forsteri, in South and Western Australia indicates that Kangaroo I. is still an important centre for the species. In order to determine changes in the abundance of the population, numbers of pups were determined at four colonies on Kangaroo Island by mark-recapture in up to five breeding seasons from 1988-89 to 1992-93. Clipping was the preferred technique for mark-recapture estimation of pups because it was quick, easy and effective. Recaptures were conducted visually; they were repeated several times in each season to improve precision of the estimates. No pups were marked between recaptures in order to minimise disturbance. Assumptions made in estimating population size by the mark-recapture technique pertinent to this study are reviewed. Pup numbers increased at three colonies: at Cape Gantheaume, from 458 to 867 over five years (with exponential rate of increase r = 0.16, n = 5); at Nautilus North, from 182 to 376 over five years (at r = 0.19, n = 4); and at North Casuarina Islet, from 442 to 503 over four years (at r = 0.043, n = 2). Rates of increase in the first two colonies are similar to those at the most rapidly increasing fur seal populations in the Southern Hemisphere. The Kangaroo I. population is estimated to be 10000 animals in 1992-93. It is likely to be at the recolonisation phase of growth, with high rates of increase at individual colonies (or parts of colonies) resulting from local immigration. As space does not appear to be limiting expansion in these colonies, fur seal numbers may continue to increase there.

Changes in the abundance of New Zealand fur seals, Arctocephalus forsteri, on the Neptune Islands, South Australia

1996 ◽  
Vol 23 (6) ◽  
pp. 697 ◽  
Author(s):  
PD Shaughnessy ◽  
I Stirling ◽  
TE Dennis
Keyword(s):  
New Zealand ◽  
South Australia ◽  
Breeding Population ◽  
The South ◽  
Mark Recapture ◽  
The North ◽  
Fur Seals ◽  
Fur Seal ◽  
New Zealand Fur Seal ◽  
Breeding Seasons

The South Neptune Island group is a well-known site for the New Zealand fur seal, Arctocephalus forsteri. A survey of seals in South Australia and Western Australia in the 1989-90 summer indicated that colonies on the South Neptunes and the adjacent North Neptunes group contained half of the breeding population in Australia. The abundance of pups at the South Neptune group was determined in four breeding seasons: 1969-70, 1988-89, 1989-90 and 1992-93. The population on Main Island increased at an exponential rate of r = 0.053 (equivalent to 5.4% per annum) between the first two surveys: counts of pups increased from 487 to 1333, and the breeding area expanded to include several new colonies. Mark-recapture estimates of pup numbers in the two largest colonies in 1989-90 and 1992-93 did not differ statistically. Rates of increase in individual colonies over the 19 or 20 years from 1970 ranged from r = 0.031 (3.1%) to r = 0.256 (29.2%). On the South Neptune Islands, the estimate of pup abundance in the most recent survey (1992-93) was 1916, on the basis of mark-recapture in most colonies and of counting in a few small ones. On the North Neptune Islands, the estimate of pup abundance in 1992-93 was 2756, on the basis of mark-recapture in most colonies. By applying a multiplier of 4.9 to convert pup numbers to an estimate of abundance of the whole population, estimates of 9400 and 13500 fur seals were obtained for the South Neptune and North Neptune Islands in 1992-93, respectively. These estimates provide a firm foundation for comparisons in future years.

Estimating brush-tailed rock-wallaby population size using individual animal recognition

2011 ◽  
Vol 33 (2) ◽  
pp. 228
Author(s):  
Karl Vernes ◽  
Stuart Green ◽  
Piers Thomas
Keyword(s):  
Population Size ◽  
National Park ◽  
New South ◽  
Morphological Characters ◽  
Population Estimates ◽  
Individual Animal ◽  
Mark Recapture ◽  
South Wales ◽  
North Eastern ◽  
Estimate Population Size

We undertook surveys of brush-tailed rock-wallabies (Petrogale penicillata) at four colonies in Oxley Wild Rivers National Park, north-eastern New South Wales, with the aim of developing a technique based upon individual animal recognition that could be used to obtain robust population estimates for rock-wallaby colonies. We identified individuals on the basis of distinct morphological characters in each colony using visual observations, and used the data within a ‘mark–recapture’ (or sight–resight) framework to estimate population size. More than 37 h of observations were made over 10 sampling days between 18 May and 9 June 2010. We could identify 91.7% of all rock-wallabies that were independently sighted (143 of 156 sightings of 35 animals). A small percentage of animals could not be identified during a visit because they were seen only fleetingly, were in dense cover, or were partly obscured by rock. The number of new animals sighted and photographed declined sharply at the midpoint of the survey, and there was a corresponding increase in resighting of known individuals. Population estimates using the mark–recapture methodology were nearly identical to estimates of total animals seen, suggesting that this method was successful in obtaining a complete census of rock-wallabies in each colony.

Aerial mark - recapture estimates of wild horses using natural markings

2008 ◽  
Vol 35 (4) ◽  
pp. 365 ◽  
Author(s):  
Michelle J. Dawson ◽  
Cameron Miller
Keyword(s):  
National Park ◽  
High Plains ◽  
Population Estimates ◽  
Small Populations ◽  
Horse Population ◽  
Mark Recapture ◽  
Aerial Surveys ◽  
Discrete Population ◽  
Over Time

Aerial mark–recapture population estimates utilising the natural markings of wild horses to identify individuals was applied in the Bogong High Plains, Alpine National Park, Victoria. A discrete population of wild horses occupying an area of 180 km2 was sampled over two days in 2005. This study explored the feasibility of a technique that aimed to enable managers to estimate the size of the horse population and monitor it over time. Four observers (including the pilot) searched for horses from a helicopter. Once horses were sighted, photographic and written observations were used to ‘mark’ each animal. The survey was repeated the following day with observations ‘recapturing’ individuals. Data were analysed using several mark–recapture estimators, and the derived population estimates ranged from 89 (±5.3, s.e.) horses to 94.7 (±7.9, s.e.) horses. We found that the method gave a level of precision relevant to management, but needs refinement. The technique and its assumptions should be tested further by increasing the number of samples and video should be used to improve identification of individuals. We believe that this is a novel application for aerial surveys, which are typically unsuitable for estimating the size of small populations. This technique was developed for horses but may be used on other conspicuous species with unique natural markings.

Australian fur seals establish haulout sites and a breeding colony in South Australia

2010 ◽  
Vol 58 (2) ◽  
pp. 94 ◽  
Author(s):  
Peter D. Shaughnessy ◽  
Jane McKenzie ◽  
Melanie L. Lancaster ◽  
Simon D. Goldsworthy ◽  
Terry E. Dennis
Keyword(s):  
Mitochondrial Dna ◽  
New Zealand ◽  
South Australia ◽  
Breeding Colony ◽  
Mitochondrial Dna Control Region ◽  
Sea Lions ◽  
Neophoca Cinerea ◽  
Fur Seals ◽  
Fur Seal ◽  
New Zealand Fur Seal

Australian fur seals (Arctocephalus pusillus doriferus) breed on Bass Strait islands in Victoria and Tasmania. They have been recorded in South Australia (SA) for many years as non-breeding visitors and on Kangaroo Island frequently since 1988, mostly in breeding colonies of the New Zealand fur seal (A. forsteri) which is the most numerous pinniped in SA. Australian fur seals have displaced New Zealand fur seals from sections of the Cape Gantheaume colony on Kangaroo Island. North Casuarina Island produced 29 Australian fur seal pups in February 2008. Australian fur seal pups were larger than New Zealand fur seal pups in the same colony and have been identified genetically using a 263-bp fragment of the mitochondrial DNA control region. North Casuarina Island has been an important breeding colony of New Zealand fur seals, but pup numbers there decreased since 1992–93 (contrary to trends in SA for New Zealand fur seals), while numbers of Australian fur seals there have increased. This study confirms that Australian fur seals breed in SA. The two fur seal species compete for space onshore at several sites. Australian fur seals may compete for food with endangered Australian sea lions (Neophoca cinerea) because both are bottom feeders.

Mitogenomics data reveal effective population size, historical bottlenecks, and the effects of hunting on New Zealand fur seals (Arctocephalus forsteri)

2017 ◽  
Vol 29 (4) ◽  
pp. 567-580 ◽  
Author(s):  
Arsalan Emami-Khoyi ◽  
Adrian M. Paterson ◽  
David A. Hartley ◽  
Laura J. Boren ◽  
Robert H. Cruickshank ◽  
...  
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Effective Population Size ◽  
Effective Population ◽  
Fur Seals ◽  
Historical Bottlenecks

Increasing abundance of pups of the long-nosed fur seal (Arctocephalus forsteri) on Kangaroo Island, South Australia, over 26 breeding seasons to 2013–14

2015 ◽  
Vol 42 (8) ◽  
pp. 619 ◽  
Author(s):  
Peter D. Shaughnessy ◽  
Simon D. Goldsworthy
Keyword(s):  
New Zealand ◽  
South Australia ◽  
Breeding Habitat ◽  
Early Nineteenth Century ◽  
Fur Seals ◽  
Fur Seal ◽  
Rate Of Increase ◽  
Subantarctic Islands ◽  
Direct Counting ◽  
Breeding Seasons

Context Long-nosed (or New Zealand) fur seals breed on the southern coast of Australia, in New Zealand and on its subantarctic islands. They are recovering from over-harvesting that occurred in the early nineteenth century. Aims We estimated the rate of increase of the population at two colonies on Kangaroo Island, South Australia: Cape Gantheaume and Cape du Couedic. Methods From 1988–89 to 2013–14, pup abundance was estimated using a mark–resight procedure with multiple resights in large aggregations of pups and by direct counting in small aggregations. Key results At Cape Gantheaume, pup numbers increased by a factor of 10.7 from 457 to 5333 over 26 breeding seasons and the exponential rate of increase averaged 10.0% per annum (p.a.). Between 1988–89 and 1997–98, the population increased at 17.3% p.a., after which the increase was 7.2% p.a. At Cape du Couedic, pup numbers increased by a factor of 12.8 from 295 to 4070 over 21 breeding seasons at 11.4% p.a. Between 1988–89 and 1997–98, the increase averaged 14.2% p.a., after which it was 9.6% p.a. These increases have been accompanied by expansion in sub-colonies that existed in January 1989 and establishment of several new sub-colonies. Increases are likely to continue on Kangaroo Island. Conclusions There are few examples of increasing population levels for Australian native mammals and this is one of the best documented. It demonstrates that fur seal populations can recover from uncontrolled harvesting provided breeding habitat ashore is protected. Implications Fur seals interfere with fishers, disturb farmed tuna in aquaculture pens, and prey on little penguins.

Seasonal oscillation in shore attendance and transience of New Zealand fur seals

1999 ◽  
Vol 77 (5) ◽  
pp. 814-823 ◽  
Author(s):  
Corey JA Bradshaw ◽  
Chris Lalas ◽  
Lyndon Perriman ◽  
Robert G Harcourt ◽  
Hugh Best ◽  
...  
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Relative Abundance ◽  
Fur Seals ◽  
Large Numbers ◽  
Fur Seal ◽  
Seasonal Oscillation ◽  
Estimate Population Size ◽  
New Zealand Fur Seal ◽  
Seasonal Oscillations

The New Zealand fur seal (Arctocephalus forsteri) appears to show regular shore attendance in the form of seasonal oscillations. This phenomenon should be quantified to properly interpret counts of fur seals >1 year old (i.e., non-pups). Here we test the predictability of peaks in the annual shore-attendance oscillation on Otago Peninsula using an autoregressive sine model and >2 years of intensive survey data. We predicted that the peak in fur seal numbers ashore would lie between 14 January - 4 April (1996) and 8 January - 2 April (1997), although this low predictability is undesirable when attempts are made to monitor population trends. Estimating population size from counts of non-pups also requires knowledge of the rate of turnover of individuals. Therefore, we tested the hypothesis that tagged animals from other colonies are immigrants to Otago Peninsula. With sightings on Otago Peninsula of fur seals tagged elsewhere in New Zealand, we used a Monte Carlo approach to simulate the expected frequency of single and multiple sightings of individuals. We found that the observed frequency of multiple sightings was significantly less than predicted by the model (P < 0.0001), indicating that tagged animals were transients. We also discovered that the sex ratio of tagged animals varied with breeding colony of origin (G1 = 52.07, P < 0.0001), suggesting that the impetus for emigration differs among colonies. We concur with the view that counting pups is the only way to estimate the relative abundance of New Zealand fur seals. In addition, we showed that counts of non-pups cannot be used to estimate population size because an unknown proportion of individuals is transient. However, counting of pups does not address the issue of estimating relative abundance for locations with large numbers of nonbreeding individuals and few or no breeders. With few or no pups it is impossible to estimate relative abundance using counts of pups.

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