New Zealand sea lion
|New Zealand sea lion|
|New Zealand (Hooker's) sea lion|
|New Zealand sea lion range|
The New Zealand sea lion (Phocarctos hookeri) also known as Hooker's sea lion or whakahao in Māori is a species of sea lion that primarily breeds on New Zealand's Sub-Antarctic Auckland and Campbell Islands and to some extent around the coast of New Zealand's South and Stewart Islands.
The New Zealand sea lion is probably the world's rarest sea lion and numbers around 10,000.
On the Auckland Islands there are three functioning rookeries. 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.
Characteristics and taxonomy
New Zealand 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.
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.
The Department of Conservation estimates that Auckland Islands' sea lions, nearly 80 per cent of the total, could be functionally extinct by 2035. 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.’
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. 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. 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.
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.’ 
Other small populations of breeding sea lions have recently begun to establish in various parts of the Stewart Island coastline.
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 exceed, 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.
In late February 2013 the first observed sea lion mortalities in the Auckland Island squid fleet in three years occurred. On two separate occasions, pre-adult sea lions appeared to have slipped through the grid at the opening of the net into its cod end. 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. In late May 2013 an adult female was also taken as incidental bycatch.
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 models. In the 2013 season the observers' coverage was of 86 per cent of tows.
Sea Lion Escape Devices
In 2001, the sea lion exclusion device (SLED) was introduced into the Auckland Island squid fishery to reduce sea lion bycatch. Since 2007, all vessels in the Auckland Islands fishery have been equipped with SLEDS.
Some scientists still do not believe sea lions survive the interaction with a SLED, 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 a 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'.
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. 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.
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|Wikimedia Commons has media related to Phocarctos hookeri.|
- New Zealand sea lion at the Department of Conservation
- Encyclopedia of New Zealand - New Zealand sea lion
- ARKive - images and movies of the Hooker's sea lion (Phocarctos hookeri)