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.

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.

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, Arctocephalus pusillus doriferus: pup numbers at Lady Julia Percy Island, Victoria, and a synthesis of the species' population status

2002 ◽  
Vol 29 (2) ◽  
pp. 185 ◽  
Author(s):  
P. D. Shaughnessy ◽  
R. J. Kirkwood ◽  
R. M. Warneke
Keyword(s):  
New Zealand ◽  
Adult Male ◽  
Arithmetic Mean ◽  
Population Status ◽  
Guard Hair ◽  
New Born ◽  
Sea Lions ◽  
Fur Seals ◽  
Fur Seal ◽  
Species Population

The abundance of Australian fur seal pups was determined at Lady Julia Percy Island in early January 2000 when the average age of pups was 5 weeks. A mark-recapture procedure with repeated recapture sessions was used to estimate abundance of pups in six accessible breeding areas. Pups (n = 1836) were marked by clipping guard hair on the head. Recaptures were conducted visually on 2-4 occasions, when a mean of 41% of sighted pups had been marked. Pup numbers were calculated using a modified Petersen estimate and combined by taking their arithmetic mean. The combined estimate in the accessible breeding areas was 4487 380 pups were counted at two inaccessible sites and 347 dead pups were recorded. Overall, the estimate of abundance for Lady Julia Percy Island was 5214 pups. This exceeds three previous estimates of doubtful veracity for pupping seasons in 1935-36, 1975-76 and 1986-87, and is the greatest number of pups recorded at any Australian fur seal colony. Summation of the most recent estimates of abundance of Australian fur seal pups in all colonies indicates pup production of 16 900 per annum in the 1990s. New Zealand fur seals were also breeding on the island (a mating and four new-born pups were recorded) and two adult male Australian sea lions were observed.

Pup production and distribution of the Australian fur seal, Arctocephalus pusillus doriferus, in Tasmania

1994 ◽  
Vol 21 (3) ◽  
pp. 341 ◽  
Author(s):  
D Pemberton ◽  
RJ Kirkwood
Keyword(s):  
Aerial Photography ◽  
The South ◽  
Mark Recapture ◽  
South Eastern ◽  
Fur Seals ◽  
Fur Seal ◽  
Production And Distribution ◽  
Breeding Seasons ◽  
Pup Mortality

In Tasmanian waters Australian fur seals, Arctocephalus pusillus doriferus, breed on five islands in Bass Strait with non-breeding haul-out sites situated in Bass Strait and along the south-eastern and southern Tasmanian coastline. Estimates of pup production were obtained over four breeding seasons between 1989 and 1993 by aerial photography, ground counts and mark-recapture censuses. Pupping commences in late October, with 90% of pups born between 2 and 20 December. Pup mortality is estimated at 15% by early January, when ground censusing was conducted. Pup production of breeding colonies in Tasmanian waters was highest in 1991, with 5130 pups estimated to have been born.

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.

scholarly journals Behavioral responses of Australian fur seals to boat approaches at a breeding colony

2018 ◽  
Vol 31 ◽  
pp. 35-52 ◽  
Author(s):  
Julia J. Back ◽  
Andrew J. Hoskins ◽  
Roger Kirkwood ◽  
John P.Y. Arnould
Keyword(s):  
Time Of Day ◽  
Species Variation ◽  
Strong Response ◽  
Approach Distance ◽  
Fur Seals ◽  
Increase Energy Expenditure ◽  
Fur Seal ◽  
Steep Decline ◽  
Breeding Seasons ◽  
Resting Behavior

In Australia, a multi-million-dollar industry is based on viewing the Australian fur seal (Arctocephaluspusillusdoriferus), predominantly through boat visits to breeding colonies. Regulation of boat approaches varies by site and no systematic investigations have been performed to inform management guidelines. To investigate possible effects of disturbance, experimental boat approaches were made to a colony at Kanowna Island in northern Bass Strait and seal responses were monitored using instantaneous scan sampling. Colony attendance (individuals remaining ashore) was found to be influenced by approach distance and time of day, but was not affected by environmental variables or season, whereas onshore resting behavior was influenced by approach distance, time of day, ambient temperature and wind direction. Onshore resting behavior decreased following experimental boat approaches to 75 m, but changes in abundance of individuals ashore were not observed at this distance. In contrast, approaches to 25 m elicited a strong response, with a steep decline in the number of individuals ashore. This response was strongest when approaches occurred in the morning, with a decline of approximately 47% of individuals, compared to a decline of 21% during afternoon approaches. With regard to onshore resting behavior, afternoon approaches to 75 m led to minimal response. The remaining three combinations of approach distance and time of day had a similar pattern of reductions in the proportion of individuals engaging in onshore resting behavior. The strongest response was again seen during approaches to 25 m conducted in the morning. These behavior changes suggest that unrestricted boat-based ecotourism at Australian fur seal colonies has the potential to increase energy expenditure and reduce the number of seals ashore. Increasing minimum approach distances to ≥75 m and/or restricting visits to afternoons may minimize these impacts at Kanowna Island during the post-molt and non-breeding seasons. As several studies have demonstrated considerable intra-species variation in seal responses to boat approaches, research at other colonies is needed before these findings can be generalized to the remainder of the Australian fur seal population.

A painter in the Bering Sea: Henry Wood Elliott and the northern fur seal

Polar Record ◽  
2013 ◽  
Vol 50 (3) ◽  
pp. 311-318
Author(s):  
Robert McCracken Peck
Keyword(s):  
Abundant Species ◽  
Historical Record ◽  
Fur Seals ◽  
Commercial Harvest ◽  
Dramatic Decline ◽  
Fur Seal ◽  
Pribilof Islands ◽  
Breeding Seasons ◽  
The U.S

ABSTRACTHenry Wood Elliott (1846–1930), a U.S. Treasury official assigned to monitor the harvest of northern fur seals on the Pribilof Islands in the 1870s, became a self-taught expert on, and defender of, the species. His careful documentation of the seals’ breeding behaviour, and of their commercial harvest, complemented by hundreds of detailed and evocative watercolours, provides a unique record of this once abundant species and the lucrative industry that revolved around it. Elliott's outspoken lobbying on behalf of the seals’ protection is often credited with saving the species from extinction. His paintings of the seals, the seal harvest, and life on the Pribilof Islands in the second half of the nineteenth century constitute an unmatched historical record of this remote region.Elliott was able to witness two full breeding seasons (and harvesting) of the fur seals during his initial stay on the Pribilofs from April 1872 to October 1873. He returned to the islands to conduct a follow-up census of the seals, on behalf of the U.S. Government, in the summer of 1874. He traveled there unofficially and at his own expense in 1876. His fourth trip to the Pribilofs was in the spring of 1890 (again on behalf of the U.S. Department of the Treasury), in response to news of a dramatic decline of the seal populations. In April, 1891, because of his public revelation of mismanagement of the fur seal harvest, Elliott was fired by the Treasury. He continued his tireless lobbying on behalf of the fur seals as a private citizen for the rest of his life. He visited the Pribilofs for the last time on behalf of the House Committee on Expenditures in the Department of Commerce and Labor in the summer of 1913. Born in Cleveland Ohio on November 13, 1846, Elliott died in Seattle Washington on May 25, 1930.

Changes in the abundance of New Zealand fur seals, Arctocephalus forsteri, in Western Australia

2000 ◽  
Vol 27 (2) ◽  
pp. 165 ◽  
Author(s):  
N. J. Gales ◽  
B. Haberley ◽  
P. Collins
Keyword(s):  
New Zealand ◽  
Western Australia ◽  
South Australia ◽  
Rate Of Change ◽  
Population Increase ◽  
Absolute Abundance ◽  
Abundance Estimate ◽  
Fur Seals ◽  
Fur Seal ◽  
Rate Of Increase

New Zealand fur seals, Arctocephalus forsteri, have been increasing in abundance in South Australia for at least the past three decades. A survey of New Zealand fur seals during the 1989/90 breeding season determined that about 20% of the Australian population bred at 16 sites in Western Australia, amounting to 1429 pups and an absolute abundance estimate of 7100 fur seals. A further survey of all fur seal colonies in Western Australia to determine current pup production and abundance estimates, and trends in pup production since the previous survey was undertaken in January 1999. Of the 17 breeding sites now known in Western Australia, 16 were surveyed and pup production had increased at all but one. The rate of change in pup production at the one unsurveyed site (West Island), was estimated as being equivalent to the mean rate of change at other sites. The estimated mean annual, exponential rate of increase (r) for all sites was 0.09, equivalent to a 9.8% annual increase in pup production and an overall increase in pup production in Western Australia of 113.3% between surveys. Total annual pup production has increased to 3090. The estimate of absolute abundance of New Zealand fur seals in Western Australia is now 15 100, in contrast to the 7100 estimated for the 1989/90 season. Mortality of pups at the time of the survey was estimated to be at least 1.3%. It is predicted that New Zealand fur seal populations will continue to increase in Western Australia. This is likely to have important management implications regarding aquaculture and fisheries activities. The increase in fur seal populations appears to be in contrast to populations of Australian sea lions, Neophoca cinerea, for which preliminary data show no evidence for a population increase. It is unknown whether the dynamics affecting these two species are related.

Separation of foraging habitat among breeding sites of a colonial marine predator, the northern fur seal (Callorhinus ursinus)

2004 ◽  
Vol 82 (1) ◽  
pp. 20-29 ◽  
Author(s):  
Bruce W Robson ◽  
Michael E Goebel ◽  
Jason D Baker ◽  
Rolf R Ream ◽  
Thomas R Loughlin ◽  
...  
Keyword(s):  
Breeding Site ◽  
Callorhinus Ursinus ◽  
Northern Fur Seal ◽  
Breeding Sites ◽  
Marine Predator ◽  
Fur Seals ◽  
Geographical Separation ◽  
Fur Seal ◽  
Satellite Transmitters ◽  
Breeding Seasons

This study examines whether lactating northern fur seals (Callorhinus ursinus) from different breeding sites on the Pribilof Islands in the eastern Bering Sea forage in separate areas. Satellite transmitters were attached to 97 northern fur seal females from nine breeding areas for 119 complete foraging trips during the 1995 and 1996 breeding seasons. Females from St. Paul and St. George islands tended to travel in different directions relative to their breeding site in both years of the study. St. Paul Island females dispersed in all directions except to the southeast, where St. George Island females foraged. Habitat separation was also observed among breeding areas on northeastern and southwestern St. Paul Island and to a lesser degree on northern and southern St. George Island. Although foraging direction led to geographical separation among sites, the maximum distance traveled and the duration of foraging trips did not differ significantly among islands in either year. The results of this study document that lactating fur seals from the same site share a common foraging area and that females from different breeding sites tend to forage in separate areas and hydrographic domains.

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