SEA snake populations at Ashmore Reef, a biodiversity hotspot off the Kimberley's coast, have dropped dramatically in numbers with some common species disappearing altogether, according to recent research.
James Cook University marine molecular ecologist Vimoksalehi Lukoschek says the change has been one of the most marked declines of a large marine vertebrate ever recorded.
Dr Lukoschek says this finding has no obvious attributable cause, and the massive drop in sea snake populations occurred well before the catastrophic Montara oil spill of 2009.
“The major declines happened between 1998 and 2002,” she says.
“Since 2005 the number of species and the number of individuals hasn’t really changed very much.”
Dr Lukoschek says high concentrations of sea snakes had been reported by colleague Dr Mick Guinea in the 1990s.
“He also started reporting the absence of some species that he’d previously seen in high numbers and also a general kind of decline in the numbers that he was seeing on his trips,” she says.
She first visited the reef, located in the Timor Sea, while doing her PhD research in 2002.
“There were some species of sea snakes which I had expected to find which had always been reported there in quite high numbers, and they weren’t there,” she says.
“It was an intensive field trip and it was unlikely we would have missed them if they had been there.”
WA Museum coral biodiversity specialist Dr Zoe Richards also noted the decline while leading the 2009 National Marine Survey of Ashmore and Cartier Reefs.
“I brought this to the attention of the Federal government in our report and recommended more specific research attention,” she says.
Dr Lukoschek made a dedicated field trip to survey sea snakes in 2010.
The team found just two species present.
“In addition to Aipysurus laevis we caught one Astrotia stokesii ,” she says.
“There were no Emydocephalus annulatus—which used to be hugely abundant.
“We manta towed 50 kilometres of reef, a huge proportion of the outer circumference, and then other areas where sea snakes have previously been reported in high numbers.”
They found snakes in just one small area of the reef complex.
“[Previously] you could go anywhere within the reef complex and within a short time you’d see sea snakes,” she says.
“There were at least seven resident species, and a total of 14 species had been recorded at Ashmore Reef at some point or another.”
She says more research is needed.
The paper: Enigmatic declines of Australia’s sea snakes from a biodiversity hotspot by Vimoksalehi Lukoschek, Maria Beger, Daniela Ceccarelli, Zoe Richards, Morgan Pratchett is published in Biological Conservation, October 2013, Pages 191–202.