Changes in the abundance and distribution of the New Zealand fur seal (Arctocephalus forsteri) in Western Australia: are they approaching carrying capacity?

Abstract

New Zealand fur seals have been increasing in abundance across Australia over the past 20 years, with annual population growth rates of 10–15%. Recent changes in distribution in Western Australia suggested that the population was increasing and expanding in range beyond the known historical distribution. We aimed to determine the growth rate of individual colonies and the overall population across Western Australia and identify new breeding and haulout sites. We used the direct count technique to estimate New Zealand fur seal pup production at 17 breeding sites. We estimated pup production to be 3518 in the 2010/11 austral summer, producing a resultant population estimate of ~17 200 New Zealand fur seals in Western Australia. This represented an exponential growth rate over the past 12 years of ~1% per annum, a significant reduction from the estimated rate of 10% per annum between 1989 and 1999. There were clusters of colonies that showed large annual declines of 6–7% in pup production over the past 12 years and at other colonies maximal rates of increase of pup production were 6–9% per annum. Three new breeding colonies were discovered. It appears that the New Zealand fur seal population is nearing its carrying capacity in Western Australia.

Intrinsic and extrinsic influences on standard metabolic rates of three species of Australian otariid

“…Australian sea lions typically forage in temperatures of 12–22°C in South Australia ( Lowther et al ., 2013 ). Male New Zealand fur seals forage in waters around Macquarie Island (54°S, 159°E), where the water temperature can be as low as 2°C, to Montague Island (36°S, 150°E) and across to western Australia (33°S, 114°E), where the water can reach 24°C ( Campbell et al ., 2014 ; McIntosh et al ., 2014 ). Australian fur seals are found predominantly in the Bass Strait, southern Australia, where water temperatures have a much smaller range of 12.6–19.3°C ( Kirkwood et al ., 2006 ; McIntosh et al ., 2014 ).…”

“…The habitats of the Australian fur seal and the Australian sea lion do not overlap, but the New Zealand fur seal occurs across both the feeding and breeding ranges of the other two species ( Page et al ., 2005a ; Campbell et al ., 2014 ). The ranges of the Australian fur seal and the New Zealand fur seal are currently expanding as they begin to reoccupy territory they held before commercial sealing ( Goldsworthy et al ., 2003 ), whereas the Australian sea lion is listed as endangered, and the population continues to decline ( McIntosh et al ., 2013 ).…”

Earthquake impacts on a protected pinniped in New Zealand

“…Calculating population abundance estimates for NZFSs has typically involved using multipliers to convert pup production estimates (Shaughnessy et al, 1994; Shaughnessy, Goldsworthy & Libke, 1995; Campbell et al, 2014; Chilvers, 2021). The previously applied multipliers of 4.76 (Goldsworthy & Page, 2007) and 4.9 (Taylor, 1982) were used here (Table 2).…”

News media portrayal of attributed stakeholder attitudes to shark management in Australia

“…Environmental factors, such as climate change-induced warmer sea-surface temperatures and/or increasing populations of shark prey species, may also contribute (Bruce, Albright, Sheehan, & Blewitt 2014;Campbell, Holley, Collins, & Armstrong, 2014;Chapman & McPhee, 2016). However, increased shark abundance is unlikely to be responsible because approximately 25% of the world's more than 500 shark species are classified as being in decline (IUCN, 2016).…”