New Zealand sea lion

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New Zealand sea lion
New Zealand Sea Lion.jpg
New Zealand (Hooker's) sea lion
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Pinnipedia
Family: Otariidae
Subfamily: Otariinae
Genus: Phocarctos
Peters, 1866
Species: P. hookeri
Binomial name
Phocarctos hookeri
(Gray, 1844)
New Zealand Sea Lion area.png
New Zealand sea lion range

The New Zealand sea lion (Phocarctos hookeri), also known as Hooker's sea lion, and whakahao in Māori, is a species of sea lion that primarily breeds on New Zealand's subantarctic Auckland and Campbell Islands and to some extent around the coast of New Zealand's South and Stewart Islands.[2]

Recent DNA information indicates the New Zealand sea lion is a lineage previously restricted to subantarctic regions. Somewhere between 1300 and 1500 AD a genetically distinct mainland lineage did not survive hunting by the first human settlers and the subantarctic lineage has since then gradually filled the ecological niche.[2]

The New Zealand sea lion is probably the world's rarest sea lion and numbers around 10,000.[3]

On the Auckland Islands there are three functioning rookeries.[4] Most sea lions are born on Dundas Island. There is a smaller rookery at Sandy Bay on Enderby Island and the smallest rookery is on Figure of Eight Island. An even smaller rookery at South East Point on Auckland Island appears to now have been abandoned. The other major breeding area is the Campbell Islands.

Sea lions are generally philopatric. They are the only species in their genus.

Characteristics and taxonomy[edit]

New Zealand sea lions, like all otariids, have marked sexual dimorphism. Adult males are 240–350 cm long and weigh 320–450 kg and adult females are 180–200 cm long and weigh 90–165 kg. At birth, pups are 70–100 cm long and weigh 7–8 kg; the natal pelage is a thick coat of dark brown hair that becomes dark gray with cream markings on the top of the head, nose, tail and at the base of the flippers. Adult females' coats vary from buff to creamy gray with darker pigmentation around the muzzle and the flippers. Adult males are blackish-brown with a well-developed black mane of coarse hair reaching the shoulders.[5]

Endangered[edit]

One of the larger New Zealand animals, it has been a protected species since the 1890s, is in decline[6] and is considered the most threatened sea lion in the world.[7]

It has been inferred from middens that the Hooker's sea lion was made locally extinct in the Chatham Islands due to predation by the Moriori.[8]

There was thought to be a population of around 15,000 in the mid-1990s. Estimates (based on the number of pups born) were about 9,000 for 2008.

In 2010 the Department of Conservation - responsible for marine mammal conservation - changed the New Zealand Threat Classification System ranking from Nationally Endangered to Nationally Critical.[9]

The Department of Conservation estimates that Auckland Islands' sea lions, nearly 80 per cent of the total, could be functionally extinct by 2035.[10][11] However the New Zealand Ministry for Primary Industries considers research on which this prediction is based is low quality and ‘should not be used in management decisions.’[12]

The January 2013 sea lion pup production count on the Auckland Islands showed the number of pups born on the islands has risen to 1931, from the 2012 figure of 1684. The 2013 number is the highest in five years.[13][14] Dead pups are also counted, since the annual pup count is used to assess the population of breeding females, but not future births when the counted pups mature.

The Campbell Islands population 'appears to be increasing slowly' and births here comprise about 20 per cent of the national total.[15] In August 2013 the seasonal southern blue whiting fleet captured 21 male sea lions in fishing grounds more than 100 kilometres off the Campbell Islands. Four were released alive. There were no captures reported by government observers the year before. The government responded to the captures by requesting the vessels trial sea lion exclusion devices (SLEDs) to reduce this by-catch.

Sea lions in the Otago Harbour

For the first time in 150 years sea lions began breeding again on the South Island coast in 1994, on the Otago Peninsula. The Otago sea lion population is currently small but estimated to reach 1000 animals by 2044, leading to issues of ‘marine protected areas, local fishing quotas and numbers management.’ [16]

Other small populations of breeding sea lions have recently begun to establish in various parts of the Stewart Island coastline and sea lions have been observed on the Catlins coast south of the Clutha River.[17]

Bycatch[edit]

In the 1990s, as the volume of squid fishing round the Auckland Islands increased, numbers of sea lions were captured as bycatch and drowned in the squid trawl nets. The government uses a modeling system to set a fishing related mortality limit (FRML) each year. If the limit is predicted to be exceeded, the Minister of Primary Industries may close the fishery. The last time the FRML was exceeded was in 2000, though there were a number of closures in the 1990s.[12]

The estimated (as different from reported) captures in the 2014 season were 11.58 per cent of the FRML.[18]

In late February 2013 the first observed sea lion mortalities in the Auckland Island squid fleet in three years occurred. Pre-adult sea lions slipped through the grid at the opening of the net into its cod end.[19] The 23 cm grid aperture is designed to hold adult sea lions in the SLED and yet still allow squid to pass into the net.[12] In 2013 one adult female was taken as incidental bycatch.[20] In the concluded 2014 season two sea lions were reported captured in the fishery.[21]

The proportion of vessels in the Auckland Island squid fishery with government observers has increased over the years, providing independent reports of bycatch based on observation rather than computer model estimates. In the 2014 season the observers' coverage was of 84 per cent of tows.[22]

Sea lion escape devices[edit]

In 2001, the sea lion exclusion device (SLED) was introduced into the Auckland Island squid fishery to reduce sea lion bycatch.[23] Since 2007, all vessels in the Auckland Islands fishery have been equipped with SLEDS.[12]

Some scientists still do not believe sea lions survive the interaction with a SLED,[24] though the Ministry for Primary Industries (MPI) believes the direct effect of fishing-related mortality on the sea lion population is minimal. MPI has concluded that a sea lion has an 85 per cent change of escaping the SLED and a 97 per cent probability of surviving a SLED escape, though it says this estimate may be 'mildly pessimistic'.[12]

Conservation advocates have supported SLED use to protect other marine animals or sharks. They include the Green Party’s Gareth Hughes and NIWA marine scientist Malcolm Francis.[25][26]

Diseases[edit]

Though the Auckland Island sea lion pup production is highly variable, a decline trend for some years followed the outbreak of the introduced bacterial disease Campylobacter in 1998 which killed an estimated 53 per cent of newborn pups and 20 per cent of adult females. In 2002, another probably introduced bacterial disease Klebsiella pneumoniae killed 32 per cent of pups, and in 2003 another 21 per cent of the pups.[27] Since 2002 Klebsiella pneumoniae bacteria have caused significant mortality in the sea lion pups at Enderby Island. Infected pups have meningitis as well as septicemia.[28]

On 12 March 2014 the Conservation Minister Nick Smith was quoted as saying there was an 'excessive focus on fishing bycatch' and 300 pups had died this summer from an as yet unidentified disease.[29]

References[edit]

  1. ^ Gales, N. (2008). Phocarctos hookeri. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 30 January 2009. Listed as Vulnerable (VU A3b)
  2. ^ a b "Research reveals New Zealand sea lion is a relative newcomer". Otago University. 14 May 2014. Retrieved 14 May 2014. 
  3. ^ "Facts about sea lion". Department of Conservation. Retrieved 8 May 2013. 
  4. ^ "DoC: 7 March 2013, CSP Technical Working Group". 
  5. ^ Perrin, William. Encyclopedia of marine mammals. 
  6. ^ "Forest & Bird condemns 40% rise in sea lion quota". Forest & Bird. 2008-12-19. Retrieved 2009-01-27. 
  7. ^ "New Zealand sea lion". NZ Department of Conservation. Retrieved 2009-01-27. 
  8. ^ McFadgen, B.G. (March 1994). "Archaeology and Holocene sand dune stratigraphy on Chatham Island". Journal of the Royal Society of New Zealand (Royal Society of New Zealand) 24 (1). doi:10.1080/03014223.1994.9517454. 
  9. ^ "Zero quota urged for sea lion". Radio New Zealand. 19 June 2010. Retrieved 20 June 2010. 
  10. ^ "New Zealand sea lion". WWF. Retrieved 25 November 2012. 
  11. ^ "NZ sea lions facing extinction in 24 years - study". nzherald.co.nz. 11 January 2012. Retrieved 25 November 2012. 
  12. ^ a b c d e "SQUID (SQU6T) – FINAL ADVICE PAP". New Zealand Ministry for Primary Industries. Retrieved 2012. 
  13. ^ "DoC: 7 March 2013m CSP Technical Working Group". 
  14. ^ "Seafood NZ: Auckland Island Sea Lion Pup Count Up For Second Year". 
  15. ^ Robertson, Bruce C. "The population decline of the New Zealand sea lion". Mammal Society: 2011. 
  16. ^ Augé, A.A; A.B. Moore, B.L. Chilvers (2012). "Predicting interactions between recolonizing marine mammals and fisheries: defining precautionary management". Fisheries Management and Ecology. doi:10.1111/j.1365-2400.2012.00861.x. 
  17. ^ "Hungry for Answers". National Institute of Water and Atmospheric Research. 
  18. ^ Ministry for Primary Industries, SQU6T Weekly Report for week ending 29 June
  19. ^ "Accidental Sea Lion Captures Regretable". Ministry for Primary Industries. 
  20. ^ Ministry for Primary Industries, SQU6T Weekly Report for week ending 26 May
  21. ^ Ministry for Primary Industries, SQU6T Weekly Report for week ending 29 June
  22. ^ Ministry for Primary Industries, SQU6T Weekly Report for week ending 29 June
  23. ^ "Sea lion bycatch in New Zealand trawl fisheries". Dragonfly Limited. Retrieved 12 February 2013. 
  24. ^ "Plan to end sea lion kill limit criticised". Otago Daily Times. Retrieved 22 February 2013. 
  25. ^ Davidson, Issac (26 Feb 2013). "Plan to save feared predator delves into murky waters". NZ Herald. 
  26. ^ "Shock over accidental catch rates". 3 News. 13 Feb 2013. 
  27. ^ Kate Mulcahy and Raewyn Peart (2012). Wonders of the Sea – the protection of New Zealand’s marine mammals. New Zealand Environmental Defence Society. p. 320. ISBN 978-0-9876660-1-7. 
  28. ^ "Staff Profile; Dr Wendi Roe". Massey University. 
  29. ^ Fox, Rebecca (12 March 2014). "300 sea lion pup deaths prompts search for answers". Otago Daily Times. 

External links[edit]