Growth and survival of New Zealand sea lions, Phocarctos hookeri: birth to 3 months

Chilvers, B. Louise; Robertson, Bruce C.; Wilkinson, I. S.; Duignan, Pádraig J.

doi:10.1007/s00300-006-0203-9

Cited by 41 publications

(32 citation statements)

References 52 publications

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“…Lactation lasts approximately 10 mo (Gales 1995), during which females split their time between foraging at sea and spending time ashore feeding their dependent pup . The absolute growth rate per day for the first 60 d of a pup's life is 151 g d -1 (Chilvers et al 2007b). This growth rate is lower than that reported for Steller Eumetopias jubatus, Californian Zalophus californianus or southern Otaria flavescens sea lions (Higgins et al 1988, Boness et al 1991, Cappozzo et al 1991, Schulz & Bowen 2004.…”

Section: Nz Sea Lion Biologycontrasting

confidence: 41%

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New Zealand sea lions Phocarctos hookeri and squid trawl fisheries: bycatch problems and management options

Chilvers¹

2008

Endang. Species Res.

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The New Zealand (NZ) sea lion Phocarctos hookeri is one of the world's most rare and highly localized pinnipeds. NZ sea lions only breed on New Zealand's subantarctic islands, with 86% of breeding occurring on the Auckland Islands (50°S, 166°E). In 1995, the sea surrounding the Auckland Islands out to 12 nautical miles (n miles) was declared a Marine Mammal Sanctuary, primarily to protect the breeding area of this species. Subsequently, in 2003, this area became a concurrent notake Marine Reserve. Both protection measures ban commercial trawl fishing within this area. Trawling is the predominant anthropogenic impact upon this species, both through direct (mortality as a result of bycatch) and potential indirect (resource competition) effects. However, despite this areabased protection and the fisheries management measures in the surrounding waters, the species, which numbers less than 12 000 ind., has shown a 30% decline in pup production over the last 8 yr. In this paper, I review the biology, foraging ecology and management of NZ sea lions in relation to the subantarctic arrow squid Nototodarus sloanii fishery to explore alternative management options within the framework of current legalisation in New Zealand. Management options need to afford better protection for this declining species, while still allowing profitable commercial fisheries operations for arrow squid in New Zealand waters.

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Section: Nz Sea Lion Biologycontrasting

confidence: 41%

“…At the Auckland Islands, mean pupping date is 26/27 December each year, with 69% of all pups born 1 wk either side of this date (Chilvers et al 2007b). Lactation lasts approximately 10 mo (Gales 1995), during which females split their time between foraging at sea and spending time ashore feeding their dependent pup .…”

Section: Nz Sea Lion Biologymentioning

confidence: 99%

New Zealand sea lions Phocarctos hookeri and squid trawl fisheries: bycatch problems and management options

Chilvers¹

2008

Endang. Species Res.

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“…For live pups, the age at sampling was known because these animals were identified and marked at birth with a plastic cap. For dead pups, the age could only be estimated based on the annual mean birth date (26 December; Chilvers et al, 2007) and the date of necropsy. Overall, the age of pups was categorized as follows: ,1 mo, 1-3 mo, and approximately 5 mo (live pups captured in May 2000) ( Table 1).…”

Section: Collection Of Samplesmentioning

confidence: 99%

Humoral Immune Response to Klebsiella Spp. In New Zealand Sea Lions (Phocarctos Hookeri) and the Passive Transfer of Immunity to Pups

Castinel

Kittelberger²,

Pomroy

et al. 2008

Journal of Wildlife Diseases

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ABSTRACT:During the 2001-02 and 2002-03 breeding seasons, epizootics of Klebsiella pneumoniae resulted in a dramatic increase of pup mortality in New Zealand sea lions (Phocarctos hookeri; NZSLs) on Enderby Island (Auckland Islands). To estimate the prevalence of infection in the NZSL population, a serologic test was developed using a Western blot and a polysaccharide antigen derived from a K. pneumoniae isolate from a NZSL pup. All archived serum samples collected between 1997 and 1998 and 2004 and 2005 at Sandy Bay Beach rookery, Enderby Island, were tested (314 pups and 302 adult females). Anti-Klebsiella antibodies were detected throughout this period, but overall, only 16% of NZSL pups between birth and 5 mo of age were seropositive compared with 95.7% of adults. There was no apparent change in antibody prevalence as a result of the two epizootics. A method to determine total immunoglobulin G (IgG) levels in sea lion serum also was developed to investigate passive immunoglobulin transfer to neonates and development of an acquired immune response. The IgG concentration was significantly lower in pups (median 2.1 mg/ml) than in adult females (median 80 mg/ml). Based on serologic results, it was not possible to determine whether K. pneumoniae was an endemic or a novel pathogen to the NZSL population because the test was not able to discriminate between Klebsiella species. However, this study suggested that the transfer of passive immunity to neonates was very low in the NZSL, especially for anti-Klebsiella antibodies.

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“…Female NZ sea lions come ashore from early December to early January, 1 to 3 d before giving birth. Mothers give birth to a single pup and remain with it for 5 to 10 d before returning to sea to forage (Chilvers et al 2007b). They then alternate between feeding at sea (1 to 5 d) and nursing the pup ashore (1 to 3 d) until pups are weaned at approximately 9 mo of age (Cawthorn et al 1985, Chilvers et al 2007b.…”

Section: Methodsmentioning

confidence: 99%

Diverse foraging strategies in lactating New Zealand sea lions

Chilvers¹,

Wilkinson²

2009

Mar. Ecol. Prog. Ser.

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Diving and foraging behaviours of marine predators are thought to be coupled with species demographics, with benthic foraging species found to have small population sizes and low growth rates. This was thought to be the case for New Zealand (NZ) sea lions Phocarctos hookeri, previously identified as solely benthic foragers with a small declining population. Female NZ sea lions dive deeper and for longer than any other otariids (eared seals). They exceed their calculated aerobic dive limits (cADL) during 68% of all dives, indicating that they are operating near their maximum physiological capacity. Recently, however, individual NZ sea lions have been found to have 2 distinct dive profile types or foraging patterns: a benthic diving profile and a deeper, more varied meso-pelagic diving profile. The ecological significance and implications of individual foraging specialisation in otariids have had limited attention in the past. Here, we compared the foraging behaviour of female NZ sea lions that use these 2 distinct dive profiles and discuss how the 2 foraging patterns may indicate differing prey choice, as well as their possible implications for individual reproductive ability and interactions with fisheries and, therefore, species demographics. Our ultimate goal is to understand the causes of this individual foraging specialisation and to incorporate such variation when determining management options for this threatened, declining species.

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Growth and survival of New Zealand sea lions, Phocarctos hookeri: birth to 3 months

Cited by 41 publications

References 52 publications

New Zealand sea lions Phocarctos hookeri and squid trawl fisheries: bycatch problems and management options

New Zealand sea lions Phocarctos hookeri and squid trawl fisheries: bycatch problems and management options

Humoral Immune Response to Klebsiella Spp. In New Zealand Sea Lions (Phocarctos Hookeri) and the Passive Transfer of Immunity to Pups

Diverse foraging strategies in lactating New Zealand sea lions

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