New Zealand's native sea lion population is declining at an alarming rate, prompting the launch of a threat management plan to try to ensure their survival.
It comes amidst a decline in several subantarctic species, a trend which scientists are at a loss to explain.
Conservation Minister Nick Smith has revealed the latest New Zealand sea lion tally is so low the Government will step in to try to address the population decline.
About 10,000 sea lions are left. They are the world's rarest sea lion and endemic to New Zealand.
This year, only 1575 sea lions were counted on the Auckland Islands, an 18 per cent drop on last year.
"Something is going on here that's not good," Smith said.
The total was the third-lowest since monitoring began in the mid-1990s and showed an ongoing decline over the last decade, he said.
"We need to step up our efforts to ensure these sea lions survive."
The cause of the decline was not clear, but a bacterial disease prevalent over the past two decades was known to have killed about 300 pups, or 20 per cent of newborns, this year.
The Department of Conservation was working on a vaccine for the disease which was akin to meningitis in humans.
Environmental change and prey abundance were also thought to have played a part while several hundred pups had died through misadventure such as falling down holes.
The effectiveness of Seal Exclusion Devices (SLEDS) used by the fishing industry to reduce the sea lion bycatch would be revisited, Smith said.
Creating new marine reserves in areas such as the Catlins, where sea lions have begun breeding, would also be explored.
Populations in other areas such as the Campbell Islands were more stable.
DOC marine scientist Debbie Freeman said the population decline was widespread.
Elephant seals, several penguin species and several bird species such as albatross, were also experiencing long-term declines.
For some the reason was obvious, such as small penguins being preyed on by cats and dogs and seabirds being caught in fisheries bycatch.
"Then for some species we just don't know what it is," Freeman said.
That it was affecting several different species suggested there was an overarching issue.
"There's a diversity of species that are showing the same general trends," Freeman said.
"But ... some of them don't appear to have any human impact on them – they're not caught in fisheries, they live on islands that are pest-free yet they're still declining."
While work was under way to try to understand the problem, marine animals were notoriously difficult to study, an issue made worse by the remote location of the subantarctic islands.
Smith said the overall population of subantarctic marine species was a concern and a proposed research base on the Auckland Islands could help solve the riddle.
The threat management plan would look at all possible reasons for the decline and ways to mitigate it.
It would be developed in conjunction with the Ministry for Primary Industries over the next year.
Smith said the southern ocean fisheries generated $100 million a year and this would need to be considered.
- Fairfax Media
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