Population growth of an endangered pinniped—the New Zealand sea lion (Phocarctos hookeri)—is limited more by high pup mortality than fisheries bycatch

2019 ◽  
Vol 76 (6) ◽  
pp. 1794-1806
Author(s):  
Sheryl Hamilton ◽  
G Barry Baker
Keyword(s):  
New Zealand ◽  
Population Growth ◽  
Population Viability Analysis ◽  
Mitigation Measures ◽  
Island Population ◽  
Sea Lion ◽  
Management Actions ◽  
Pup Mortality ◽  
Campbell Island ◽  
Phocarctos Hookeri

Abstract The endangered New Zealand sea lion, Phocarctos hookeri is killed as incidental bycatch in a trawl fishery operating near their second largest population on Campbell Island in New Zealand’s sub-Antarctic. Using the Potential Biological Removal (PBR) procedure to assess the sustainability of this bycatch for the sea lion population on Campbell Island indicated that annual bycatch estimates, particularly following the implementation of bycatch mitigation measures, are below the PBR threshold of 25 (derived using a precautionary approach). Preliminary Population Viability Analysis (PVA) modelling supported the finding that current bycatch levels, especially given a strong male bias (98%) in bycatch, are sustainable for this population. Models showed that reducing pup mortality through management actions, such as installing ramps in wallows where large numbers of pups drown, would lead to increased population growth. While obtaining more accurate data on population status and demographic parameters for the Campbell Island population should be a priority, this will take many years of research. The PBR and PVA tools demonstrate that contemporary conservation management should continue to focus on increasing pup survival while maintaining mitigation approaches that have reduced bycatch to low levels, together with high observer coverage to sustain confidence in annual bycatch estimates.

Abundance, distribution and status of the New Zealand sea lion, Phocarctos hookeri

1999 ◽  
Vol 26 (1) ◽  
pp. 35 ◽  
Author(s):  
Nicholas J. Gales ◽  
David J. Fletcher
Keyword(s):  
New Zealand ◽  
Breeding Site ◽  
Close Monitoring ◽  
Sea Lion ◽  
Trawl Fishery ◽  
Mitigation Action ◽  
Breeding Seasons ◽  
Pup Mortality ◽  
Campbell Island ◽  
Phocarctos Hookeri

The abundance of the New Zealand sea lion, Phocarctos hookeri, was estimated using a model that incorporated estimated pup production. Pups are born at only five sites, four of which are at the sub-Antarctic Auckland Islands, which lie to the south of New Zealand. The remaining breeding site is at Campbell Island in the same region. Pup production was estimated during the 1994/95 and 1995/96 breeding seasons from mark–recapture studies at the two largest sea lion rookeries, at the Auckland Islands (Sandy Bay and Dundas Island), which account for almost 90% of total pup production for the species. Pup production for the other sites was estimated from direct counts or, in the case of Campbell Island, from recent tagging data. Total pup production estimates for all sites during the 1994/95 and 1995/96 breeding seasons are 2640 and 2807 respectively. During the four-week pupping season, pup mortality at most sites was estimated to be about 10%. The estimates of absolute abundance based on pup production for the two breeding seasons were 11 700 (95% confidence interval (CI): 10 500–13 100) and 12 500 (95% CI: 11 100–14 000) respectively. This population abundance is among the smallest reported for a species within the Otariidae. The highly localised, and historically reduced distribution make this species vulnerable to impact and warrants particular attention from conservation managers. In particular, the potential impact of the annual bycatch of P. hookeri in a trawl fishery requires close monitoring and, ideally, some mitigation action.

Foraging energetics and diving behavior of lactating New Zealand sea lions, Phocarctos hookeri

2000 ◽  
Vol 203 (23) ◽  
pp. 3655-3665 ◽  
Author(s):  
D.P. Costa ◽  
N.J. Gales
Keyword(s):  
New Zealand ◽  
Metabolic Rate ◽  
Dive Depth ◽  
Diving Behavior ◽  
Metabolic Rates ◽  
Sea Lion ◽  
Water Turnover ◽  
Sea Lions ◽  
The Mean ◽  
Phocarctos Hookeri

The New Zealand sea lion, Phocarctos hookeri, is the deepest- and longest-diving sea lion. We were interested in whether the diving ability of this animal was related to changes in its at-sea and diving metabolic rates. We measured the metabolic rate, water turnover and diving behavior of 12 lactating New Zealand sea lions at Sandy Bay, Enderby Island, Auckland Islands Group, New Zealand (50 degrees 30′S, 166 degrees 17′E), during January and February 1997 when their pups were between 1 and 2 months old. Metabolic rate (rate of CO(2) production) and water turnover were measured using the (18)O doubly-labeled water technique, and diving behavior was measured with time/depth recorders (TDRs). Mean total body water was 66.0+/−1.1 % (mean +/− s.d.) and mean rate of CO(2) production was 0. 835+/−0.114 ml g(−)(1)h(−)(1), which provides an estimated mass-specific field metabolic rate (FMR) of 5.47+/−0.75 W kg(−)(1). After correction for time on shore, the at-sea FMR was estimated to be 6.65+/−1.09 W kg(−)(1), a value 5.8 times the predicted standard metabolic rate of a terrestrial animal of equal size. The mean maximum dive depth was 353+/−164 m, with a mean diving depth of 124+/−36 m. The mean maximum dive duration was 8.3+/−1.7 min, with an average duration of 3.4+/−0.6 min. The deepest, 550 m, and longest, 11.5 min, dives were made by the largest animal (155 kg). Our results indicate that the deep and long-duration diving ability of New Zealand sea lions is not due to a decreased diving metabolic rate. Individual sea lions that performed deeper dives had lower FMRs, which may result from the use of energetically efficient burst-and-glide locomotion. There are differences in the foraging patterns of deep and shallow divers that may reflect differences in surface swimming, time spent on the surface and/or diet. Our data indicate that, although New Zealand sea lions have increased their O(2) storage capacity, they do not, or cannot, significantly reduce their at-sea metabolic rates and are therefore likely to be operating near their physiological maximum.

Philopatry and site fidelity of New Zealand sea lions (Phocarctos hookeri)

2008 ◽  
Vol 35 (5) ◽  
pp. 463 ◽  
Author(s):  
B. Louise Chilvers ◽  
Ian S. Wilkinson
Keyword(s):  
New Zealand ◽  
Site Fidelity ◽  
Breeding Area ◽  
Quantitative Investigation ◽  
Sea Lion ◽  
Breeding Sites ◽  
Auckland Island ◽  
Sea Lions ◽  
Breeding Habitats ◽  
Phocarctos Hookeri

The New Zealand sea lion (NZ sea lion), Phocarctos hookeri, is New Zealand’s only endemic pinniped, and one of the worlds rarest otariids. It is classified as ‘Threatened’ based primarily on the low number of breeding sites and restricted distribution. In New Zealand, a species listed as ‘threatened’ is required to be managed to allow its recovery and removal from the list within 20 years. For NZ sea lions this is dependant on the establishment of new breeding areas. However, understanding the recolonisation processes for pinnipeds is still in its infancy with factors such as philopatry needing more research to understand individual dispersal and the recolonisation process. This paper presents the first quantitative investigation into the level of site fidelity and philopatry to breeding beaches in NZ sea lions. Data from resights of NZ sea lions marked as pups from the northern Auckland Island breeding area suggest that both site fidelity and philopatry are important characteristics of this species. Our results show that overall: (1) females have a higher resighting rate than males, particularly at natal sites; (2) female non-natal resightings are predominantly restricted to locations within the northern Auckland Island breeding area (an area of ~10 km2), whereas male resightings are more widely dispersed (up to 700 km to NZ mainland); and (3) philopatry occurs for both sexes, but is more predominant in females than males, with males displaying delay related to sexual and social maturity. The colonisation of new breeding habitats rarely occurs when philopatry is strong and population density is low, stable or declining such as seen for NZ sea lions. Therefore, this research indicates that management of NZ sea lions needs to minimise anthropogenic mortality and encourage population growth to maximise density at breeding sites and encourage females to disperse to establish new breeding areas.

scholarly journals Pup mortality in New Zealand sea lions (Phocarctos hookeri) at Enderby Island, Auckland Islands, 2013-18

PLoS ONE ◽  
2019 ◽  
Vol 14 (11) ◽  
pp. e0225461
Author(s):  
Sarah A. Michael ◽  
David T. S. Hayman ◽  
Rachael Gray ◽  
Ji Zhang ◽  
Lynn Rogers ◽  
...  
Keyword(s):  
New Zealand ◽  
Sea Lions ◽  
Pup Mortality ◽  
Phocarctos Hookeri

scholarly journals Extensive variation at MHC DRB in the New Zealand sea lion (Phocarctos hookeri) provides evidence for balancing selection

Heredity ◽  
2013 ◽  
Vol 111 (1) ◽  
pp. 44-56 ◽  
Author(s):  
A J Osborne ◽  
M Zavodna ◽  
B L Chilvers ◽  
B C Robertson ◽  
S S Negro ◽  
...  
Keyword(s):  
New Zealand ◽  
Balancing Selection ◽  
Sea Lion ◽  
Extensive Variation ◽  
Phocarctos Hookeri

New Zealand sea lion (Phocarctos hookeri) epidemic 2002

2003 ◽  
Vol 51 (1) ◽  
pp. 45-46 ◽  
Author(s):  
PJ Duignan ◽  
I Wilkinson ◽  
MR Alley
Keyword(s):  
New Zealand ◽  
Sea Lion ◽  
Phocarctos Hookeri

scholarly journals Historical population size of the threatened New Zealand sea lion Phocarctos hookeri

2015 ◽  
Vol 97 (2) ◽  
pp. 436-443 ◽  
Author(s):  
Catherine J. Collins ◽  
B. Louise Chilvers ◽  
Matthew Taylor ◽  
Bruce C. Robertson
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Effective Population Size ◽  
Carrying Capacity ◽  
Effective Population ◽  
Sea Lion ◽  
Sea Lions ◽  
Target Values ◽  
Phocarctos Hookeri

Abstract Marine mammal species were exploited worldwide during periods of commercial sealing in the 18th and 19th centuries. For many of these species, an estimate of the pre-exploitation abundance of the species is lacking, as historical catch records are generally scarce and inaccurate. Genetic estimates of long-term effective population size provide a means to estimate the pre-exploitation abundance. Here, we apply genetic methods to estimate the long-term effective population size of the subantarctic lineage of the New Zealand sea lion (NZ sea lion), Phocarctos hookeri . This species is predominantly restricted to the subantarctic islands, south of mainland New Zealand, following commercial sealing in the 19th century. Today, the population consists of ~9,880 animals and population growth is slow. Auckland Island breeding colonies of NZ sea lion are currently impacted by commercial trawl fisheries via regular sea lion deaths as bycatch. In order to estimate sustainable levels of bycatch, an estimate of the population’s carrying capacity ( K ) is required. We apply the genetically estimated long-term effective population size of NZ sea lions as a proxy for the estimated historical carrying capacity of the subantarctic population. The historical abundance of subantarctic NZ sea lions was significantly higher than the target values of K employed by the contemporary management. The current management strategy may allow unsustainable bycatch levels, thereby limiting the recovery of the NZ sea lion population toward historical carrying capacity.

scholarly journals Risk Factors for New Zealand Sea Lion (Phocarctos hookeri) Pup Mortality: Ivermectin Improves Survival for Conservation Management

2021 ◽  
Vol 8 ◽  
Author(s):  
Sarah A. Michael ◽  
David T. S. Hayman ◽  
Rachael Gray ◽  
Wendi D. Roe
Keyword(s):  
Risk Factors ◽  
Risk Factor ◽  
New Zealand ◽  
Active Management ◽  
Ivermectin Treatment ◽  
Treatment Trial ◽  
Sea Lions ◽  
Systemic Spread ◽  
Pup Mortality ◽  
Phocarctos Hookeri

Septicaemia due to hypervirulent (HV) Klebsiella pneumoniae is the leading cause of neonatal pup mortality in endangered New Zealand sea lions (Phocarctos hookeri) at Enderby Island, in the New Zealand sub-Antarctic. Accounting for approximately 60% of annual pup mortality at this site following an epizootic event in 2001–02, HV K. pneumoniae is also emerging worldwide as a significant community-acquired human pathogen. To facilitate efficient direct mitigation to reduce pup mortality, a case-control study and prospective cohort study were conducted to identify risk factors amenable to active management. Additionally, to investigate impacts of hookworm (Uncinaria spp.), a nested treatment trial with the anthelmintic ivermectin was undertaken concurrently. During two austral summer field seasons (2016–2018), 698 pups were captured for treatment trial recruitment and the collection of morphometric measurements, biological samples and risk factor data. Gastrointestinal carriage of the virulent phenotype of K. pneumoniae was a consistent risk factor, while ivermectin treatment and higher body condition index consistently reduced risk of HV K. pneumoniae mortality. Significantly fewer ivermectin-treated pups were found dead (24.1% control, 11.1% treatment), with a trend towards a higher proportion of HV K. pneumoniae deaths amongst the control group. This study provides evidence to support ivermectin treatment as a pup mortality mitigation strategy in New Zealand sea lions at Enderby Island. If applied to larger colonies where HV K. pneumoniae and hookworm impact pup survival, this intervention could have population-scale benefits for this endangered species. Further work is required to understand how ivermectin prevents HV K. pneumoniae septicaemia, but removal of hookworms before intestinal mucosal damage occurs could limit systemic spread of virulent bacteria from the gastrointestinal tract.

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