AUSTRALIAN BROADCASTING CORPORATION 09 December 13 The mystery of Ashmore Reef's disappearing sea snakes (Ben Collins)
When Dr Vimoksalehi Lukoschek started her research on the evolution of sea snakes she needed a location with plenty of animals to study. Ashmore Reef was an obvious choice. Lying about halfway between Australia's Kimberley coast and East Timor, Ashmore Reef National Nature Reserve was renowned for being a sea snake hot spot. Previous surveys had found high numbers of sea snakes of a huge variety, some not found anywhere else in the world.
But instead of studying sea snake evolution, Dr Lukoschek found that she was documenting the disappearance of one of Ashmore Reef's natural wonders.
"In '73 there were up to 45 snakes seen per day and about eight or nine species. And then in 2002 when I was there we only saw 20 snakes a day and only four species. And in 2010 we saw a grand total of just 45 snakes over a ten day period, and essentially just one species. So the message, I guess, from that is that there's been a massive and unprecedented decline in the diversity and abundance of sea snakes at Ashmore Reef," she says.
Where have all the sea snakes gone?
Of all the remote reefs of North Western Australia, Ashmore is perhaps the last one you'd expect an entire group of marine animals to disappear from. Fishing has been restricted since the Ashmore Reef National Nature Reserve was established in 1983. Conservation status was increased in 2002 when the nature reserve was Ramsar Listed.
It's one of the few locations in the North East Indian Ocean with constant surveillance. The low-lying sand cay became a prominent destination for asylum seekers from around 2001, and there is a permanent Customs presence.
That Ashmore Reef is one of the best studied, and most protected locations in the North East Indian Ocean allows researchers to rule out all the likely causes of the decline.
"Ashmore Reef's been a marine protected area since the early 1980s and it's been closed to all fishing. There's no illegal Indonesian fishing that goes on there," Dr Lukoschek says.
Coral bleaching has had a big impact on reefs around the world, and yet Ashmore Reef has been particularly resilient.
"Australia-wide or even globally, there were these large bleaching events of coral. In 1998 Ashmore Reef wasn't particularly, strongly affected; in fact it seemed to be almost unaffected in 1998. In 2002 there was bleaching at Ashmore Reef, but the sea snake declines were already well and truly underway by then," says Dr Lukoschek.
"It's certainly puzzling to me why snakes have disappeared from Ashmore Reef, which is a marine protected area. Whereas at Scott Reef, which is about 400 kilometres away, which isn't a marine protected area, there's not evidence of similar declines... There isn't routine monitoring for sea snakes at Scott Reef, but anecdotally it seems that people still see them there," says Dr Lukoschek.
But the cause of Ashmore Reef's missing sea snakes remains a mystery.
"There's no long-term monitoring there of things that may cause loss of large predators. So the answer is 'we don't know why'. There's a few likely candidates that could be related to disease, could be related to some decline in habitat quality or prey abundance. But there's definitely no firm evidence for anything in particular."
Does anybody really care?
Many people have an instinctive fear of land snakes, and Dr Lukoschek says that sea snakes are typically highly venomous.
"So if you get bitten, it's quite likely to be fatal."
But Dr Lukoschek adds that this scenario is highly unlikely.
"They're less likely to bite out of fear because they don't have many natural predators in the wild."
"The sea snakes we have around Australia evolved from Australian land snakes. So their nearest living relatives are snakes like brown snakes and black snakes," says Dr Lukoschek.
Despite evolving eel-like paddle tails, sea snakes still have lungs rather than gills.
"They have to come to the surface on average once every one hour to two hours... They do actually get some oxygen through their skin from the ocean," she says.
Sea snakes are harvested for traditional medicine in parts of South East Asia, but overall they are economically insignificant.
"Compared to, if we lost fish or fisheries, or if we lost coral reefs; the loss of seas snakes probably wouldn't affect humans very greatly," says Dr Lukoschek.
But if the extinction of an animal concerns you, even a venomous snake that lives somewhere you're not likely to ever visit, then the loss of Ashmore Reef's sea snakes is a problem.
"At least three of the species that occur at Ashmore Reef occur in very few other places in the world," Dr Lukoschek says.
"Because sea snakes are predators, the loss of any kind of top predator often signals a high biodiversity loss throughout the food chain."
There's also the risk that the fate of Ashmore Reef's sea snakes is indicative of a widespread problem.
"There's no long-term monitoring going on for sea snakes, pretty much anywhere. They could be disappearing, we just don't know," Dr Lukoschek says.
The bleak reality for sea snakes is that their greatest hope for a future lies in our lack of knowledge about what's really happening. New populations of sea snakes thought to be facing extinction after disappearing from Ashmore Reef, have recently been found on the West Australian coast.
But Dr Lukoschek says that as long as sea snake disappearances remain a mystery, little can be done.
"In terms of Ashmore Reef itself, there isn't really much managers can do because it's hard to put a management action into place if you don't know why something has happened."
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