New Zealand sea lion
The New Zealand sea lion, once known as Hooker's sea lion, and as pakake or whakahao and kake in Māori, is a species of sea lion that is endemic to New Zealand and primarily breeds on New Zealand's subantarctic Auckland and Campbell islands, and have in recent years been slowly breeding and recolonising around the coast of New Zealand's South and Stewart islands. The New Zealand sea lion numbers around 12,000 and is one of the world's rarest sea lion species. They are the only species of the genus Phocarctos.
Physiology and behaviour
New Zealand sea lions are one of the largest New Zealand animals. Like all otariids, they have marked sexual dimorphism; adult males are long and weigh, while adult females are long and weigh. At birth, pups are long and weigh ; 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 grey 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. New Zealand sea lions are strongly philopatric.The New Zealand sea lion's terrestrial behaviour is unique among other pinniped species. In the breeding season, female New Zealand sea lions gradually move inland with their pups to protect them from harassment by males, wind, storms, and potential parasitic infections. They can move up to inland, from sandy beaches to tall grasses, and into forests. They are the only pinniped species known to disperse far inland and have a preference for forests. As mainland populations have grown since the 1990s, this behaviour has led to an increasing incidence of sea lions entering human spaces.
Distribution
The main breeding populations are at the Auckland and Campbell Islands in the New Zealand subantarctic, where approximately 99% of the species' annual pup production occurs. There are currently three functioning breeding rookeries on the Auckland Islands. Most sea lions are born on Dundas Island. A smaller rookery exists 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.Historically, New Zealand sea lions were distributed all over mainland New Zealand and Stewart Island, but were extirpated from these areas due to human hunting activities. For the first time in over 150 years, sea lions began breeding again on the South Island coast in 1993, on the Otago Peninsula after Mum gave birth. Other small populations of breeding sea lions have recently begun to establish in various parts of the Stewart Island coastline and have been observed on the Catlins coast south of the Clutha River.
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 was wiped out by the first Maori settlers, and the subantarctic lineage has since then gradually filled the ecological niche. It has been inferred from middens and ancient DNA that a third lineage was made extinct at the Chatham Islands due to predation by the Moriori people.
Diet and predation
New Zealand sea lions are known to prey on a wide range of species including fish such as Antarctic horsefish, red cod, opalfish and Patagonian toothfish, rays, sharks, cephalopods, crustaceans, seabirds and other marine mammals, and even New Zealand fur seals. Studies indicate a strong location effect on diet, with almost no overlap in prey species comparing sea lions at Otago Peninsula and Campbell Island, at the north and south extents of the species' breeding range. New Zealand sea lions are in turn preyed on by great white sharks, with 27% showing evidence of scarring from near-miss shark attacks in an opportunistic study of adult New Zealand sea lions at Sandy Bay, Enderby Island.Status
New Zealand sea lions are considered the most threatened sea lion in the world. The species' status is largely driven by the main breeding population at the Auckland Islands, which declined by ~50% between 2000 and 2015. The 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 was the highest in five years. The Campbell Island population 'appears to be increasing slowly' and births here comprise ~30% of the species' total. The Otago and Stewart Island sea lion populations are currently small, though increasing. Population estimates for the whole species declined from ~15,000 in the mid-1990s to 9,000 in 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% 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'. In 2015, the International Union for Conservation of Nature changed the classification of this species to "Endangered", based on low overall population size, the small number of breeding populations and the projected trend of the Auckland Islands breeding population.
In 2019, the New Zealand sea lion's status was found to have improved and they are now "Nationally Vulnerable". Their overall rate of population decline has slowed in most breeding locations and Stewart Island was officially recognised as a new breeding colony in 2018. Their global IUCN status remains "Endangered".
File:New Zealand Sea Lions at The Spit, Aramoana.jpg|thumb|Sea lions on Aramoana in the Otago Harbour
Threats
Subsistence hunting and commercial sealing
Subsistence hunting and commercial harvest of sea lions greatly reduced the breeding range and population size of New Zealand sea lions between the 13th and 19th Centuries. In 1893, sealing for both New Zealand sea lions and New Zealand fur seals was prohibited by law in New Zealand. In their book The Animals of New Zealand, Frederick Hutton and James Drummond described the hunt for the New Zealand sea lion:—The Auckland Islands were the scene of sealing activity for many years, the first expeditions setting out from Sydney early in the nineteenth century. The industry, which was conducted on a large scale, reached the height of its prosperity between 1810 and 1820. The sealers had to suffer great hardships, but they were attracted by the lucrative trade, and large numbers of seals were slaughtered in the race for wealth.
Commercial fishery bycatch
In the 1990s, as the volume of squid fishing around the Auckland Islands increased, numbers of sea lions were captured as bycatch and drowned in the squid trawl nets. The government uses a modelling system to set a fishing-related mortality limit 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 a number of closures occurred in the 1990s.In late February 2013, the first observed sea lion mortalities in the Auckland Island squid fleet in three years occurred. Juvenile sea lions 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 2013, one adult female was taken as incidental bycatch.
In August 2013, the seasonal southern blue whiting fleet captured 21 male sea lions in fishing grounds more than 100 km off the Campbell Islands. Four were released alive. No captures were reported by government observers the year before. The government responded to the captures by requesting the vessels try sea lion exclusion devices to reduce this bycatch.
The estimated captures in the 2014 season were 11.58% of the FRML. 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. During the 2014 season, the observers' coverage was of 84% of tows. In the concluded 2014 season, two sea lions were reportedly captured in the fishery.