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Research adds cautionary note to seal success story

27/07/2017 11:30:00 a.m.


New Lincoln University research* is highlighting conservation issues around the recovery of the New Zealand fur seal after centuries of overexploitation.

It involved reconstructing the demographic history of the seals using maternally inherited, mitochondrial DNA sequences.
 
Associate professor Adrian Paterson said samples were obtained from 186 fur seals from around New Zealand and the Bounty Islands in the Sub Antarctic.
 
“We got information from whole mitochondrial genomes for each of these seals which allowed us to look at how genetically different the various colonies and areas were from each other.”
 
Results showed a seal population of up to 3,000,000 in pre-human New Zealand— twice as large as estimated previously.
Hunting, and then commercial sealing reduced it to 10,000 by the end of the 19th century.

“This pre-human population figure gives us an estimate for the best (or worst) case scenario for seal population growth,” Associate Professor Paterson said.

Conservation measures have led to a recovery. The estimate for the New Zealand fur seal population in 2015 was about 200,000 individuals, approximately 6 per cent of the pre-human population.
 
Associate Professor Paterson said fur seals have effectively gone beyond the conservation phase and are a self-managing population.
 
“They are one of the few New Zealand native species success stories.”
 
However, they increasingly spill over into areas used by humans for fishing, swimming and recreation.
 
 “As fur seal numbers increase they are setting up new colonies in new areas, and moving into new regions where they have seldom been seen. Fur seals are also generalist feeders whose diet does include commercially important species.
 
“It is very likely that the fur seal population can, and will, continue to grow considerably from what we see today. So in future we will see more seals, new colonies in areas settled by humans, and some competition for fish species of interest to humans. In short, lots of wildlife management issues to solve so that humans and seals can continue to live together.”
 
He said the question of what size population is both acceptable and manageable in a modern
New Zealand is one that needs to be addressed further.

*Mitogenomics data reveal effective population size, historical bottlenecks, and the effects of
hunting on New Zealand fur seals (Arctocephalus forsteri)
 

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