A short shark shock

by Rebecca Priestley / 20 June, 2013
Shark populations are surprisingly vulnerable – and shark-finning is a serious threat.
Photo/Thinkstock


One of the most unlikely things I did last year was snorkelling with sharks. On previous snorkelling excursions, I’d been ready to get out of the water if I saw a shark. But here, in the Kermadec Islands, roughly halfway between New Zealand and Tonga, sharks were pretty much guaranteed.

I was with a team of scientists, including Department of Conservation shark specialist Clinton Duffy, collecting seaweeds, coral and starfish from the waters around the Meyer Islands. It was August, and I’m not sure if the involuntary gasp I gave as I plunged into the water was because of the cold or because the first thing I saw swimming beneath me was a Galapagos shark. That one was a baby; the second one I saw, patrolling a deep rocky hole lined with pink coralline algae, was 1.5m long, and soon there were four sharks in the water with us.

Duffy, who is researching the conservation biology of great white sharks for a PhD in marine science, says sharks are a sign of a healthy marine ecosystem. The waters for 12 nautical miles around each of the Kermadec islands are marine reserves and, unlike most New Zealand marine environments, are largely unaltered by fishing.

Sharks suffer from fishing for the same reasons as marine turtles and marine mammals, says Duffy. “They are long-lived species with generally low biological productivity – the females often don’t mature until half their life expectancy, then only breed every second or third year. That’s fine in a species that’s an apex predator – they don’t need to replace themselves very rapidly because almost nothing else is eating them. But when you put fishing pressure onto a species like that, they can’t sustain a great deal of take.”

But of our 112 species of sharks and rays, 73 are commercially fished. Some of these – including vulnerable species – are caught solely for their fins, with $4.5 million worth exported each year, mostly to Hong Kong.

The New Zealand Shark Alliance, which says we need to do more to protect our sharks from fishing, is calling for New Zealand to join the 98 countries that have already banned shark-finning. They are also calling for changes to the Quota Management System, which currently manages only 11 shark species. “For some shark species, it’s been estimated that you can only sustainably fish the population down about 5% below the unfished biomass,” says Duffy.

Many island territories, including the Cook Islands, Tokelau and Tahiti, have created extensive marine sanctuaries that offer full protection for sharks. Although the waters around the Kermadec Islands are among the most protected in New Zealand, even that might not be enough for its sharks, says Duffy. “The issues up there include expansion of drop-lining and tuna long-lining. Most of the Galapagos shark habitat is protected within the marine reserve, but fishing between the islands outside the reserve could still deplete the shark population.”

International experience – some Atlantic populations have completely collapsed under fishing pressure – has shown shark populations are very vulnerable. “In the long term I would like to see an enlarged continuous marine reserve that took in all of the Kermadec Islands, and more of the deep water between the islands.”

Pew Environment Group, WWF and Forest & Bird are calling for full protection of the Kermadec waters, out to the 200-nautical-mile extent of the exclusive economic zone. Along with banning shark-finning, and better quota management, creating more ocean sanctuaries will help to protect New Zealand’s sharks, as well as other big predatory fish like kingfish and grouper.

www.nzsharkalliance.org.nz
www.thekermadecs.org

Send questions to science@listener.co.nz
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