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New Zealand Journal of Marine and Freshwater Research abstracts

Distribution, abundance and growth of New Zealand sea lion Phocarctos hookeri pups on Campbell Island

Simon Childerhouse 1
Nadine Gibbs 1
Gus McAlister 2
Shaun McConkey 3
Helen McConnell 1,3
Nathan McNally 1
David Sutherland 4

1Department of Conservation
P.O. Box 10420
Wellington, New Zealand

25 Blue Cliffs Beach Rd
RD 1
Tuatapere, New Zealand

3New Zealand Sea Lion Trust
76 Elm Row
Dunedin, New Zealand

479/4 Alice St
Invercargill, New Zealand

Abstract  Nine weeks field work was completed during two trips in January/February and March/April 2003 to investigate the distribution and abundance of New Zealand sea lion Phocarctos hookeri pups at Campbell Island. A total of 161 pups were tagged and a further 138 dead pups were found. A closed mark-recapture model was used to estimate the total number of live pups (e.g., tagged plus untagged pups) at Campbell Island in April as 247 (SE = 28, 95% CI 198-308). Pup production at Campbell Island is estimated at 385, which comprises 13% of the total pup production for the species in the 2003 season. This is the first robust estimate of pup production for New Zealand sea lions at Campbell Island. The figure of 385 pups is considerably higher than any of the previous estimates reported from Campbell Island. The high level of pup mortality (36%) at Campbell Island for approximately the first 2 months after birth is higher than the 17% reported for the Auckland Islands for approximately the same period in 2003, but is similar to unusually high levels of mortality (20-30%) reported at the Auckland Islands in recent years. It was not possible to determine the cause of death of the 138 dead pups owing to scavenging and decomposition. Pups were found over the whole Island, with the exception of its northern end. Male pups were significantly heavier and faster growing than female pups over the same period.

Keywords  Phocarctos hookeri; subantarctic; sea lion; New Zealand; Campbell Island; survey; breeding; distribution; abundance; pup growth

M04151; Online publication date 17 June 2005 Received 2 November 2004; Accepted 28 January 2005
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39: 889-898
0028-8330/05/3904-0889 © The Royal Society of New Zealand 2005

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