THE mystery surrounding the spate of 'corkscrew' seal deaths in Scottish waters has spilled over into a war of words between conservationists and the Scottish and UK governments.
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It is still not known what is killing the seals and leaving strange corkscrew shaped injuries on their bodies. Some think it is seals cannibalising each other, others that it is ship propellers.
Now, a coalition of wildlife and conservation groups is urging the Scottish and UK governments to withdraw advice to the shipping industry that they believe could see more seals killed by corkscrew injuries.
Official advice was changed last month after researchers found evidence that an adult male grey seal in the Firth of Forth had killed and cannibalised young grey seals and left distinctive spiral lacerations around their bodies. Before that, ships using ducted propellers had been blamed by scientists for the horrific corkscrew wounds, thought to have killed at least 100 seals in Scotland.
But now 19 environmental groups are saying that propellers can not be ruled out as causes of injury so it is "premature" to change shipping advice. Previous precautionary warnings not to use ducted propellers near seal conservation areas and to avoid the breeding season should be reinstated, they say.
New advice, given internally to staff at Scottish Natural Heritage and other government wildlife agencies across the UK, concludes that ducted propellers may not be responsible for corkscrew injuries, however. "Therefore mitigation measures and monitoring may not be necessary," it says.
But the new advice also accepts that that "it would be premature to completely discount the possibility that some of the corkscrew injuries are caused by interactions with propellers".
This has been seized on by campaigners worried that seals could still be killed by propellers. "We need to do more, not less, to turn around the declines in seals, so the ... advice is premature and inappropriate," said Sarah Dolman, Northeast Atlantic programme manager for Whale and Dolphin Conservation.
"We urgently need a UK-wide strategy to recover seal populations that should include monitoring at haul-out sites, post-mortem examinations to determine all causes of death and peer-review of all previous work on corkscrew injuries including historical analysis. Precautionary mitigation guidance should be in place until all causes of death are clearly understood."
There are particular concerns over harbour seals, which have suffered steep declines around Scotland in recent years. Populations on the east coast and in Orkney and Shetland plummeted by up to 85 per cent between 2000 and 2010.
Conservationists point out that there is no evidence to date that grey seals are killing adult harbour seals with corkscrew injuries. More than 30 of those found with the injuries have been harbour seals.
The shipping industry, however, attacked campaigners for ignoring the new evidence on seal predation. "It is frustrating that now the evidence does not suit their theories they continue to blame the industry regardless," said David Balston, policy director at the Chamber of Shipping.
"The evidence now shows natural factors are to blame for seal deaths. It is time environmental campaign groups stopped demonising the industry," he argued. "We should have a constructive debate but one that is based on science and evidence, not ideology."
According to the Scottish Government, the new research was clear evidence that grey seals were likely to be the main cause of corkscrew deaths, rather than propellers. "However Marine Scotland will continue to monitor our seal population for further injuries and any evidence about the causes," said a government spokeswoman.
"We will continue to monitor interactions between harbour seals and shipping, including the potential for any disturbance or collisions."
The government is funding a major research project to identify the causes of the decline in harbour seals.
Evidence of another possible cause of seal deaths has been uncovered by scientists from the University of St Andrews and elsewhere. They found high levels of toxins from algal blooms in harbour seals and concluded that they could have been poisoned by eating contaminated fish.
"We suggest that exposure to these toxins are likely to be important factors driving the harbour seal decline in some regions of Scotland," they say in an article in the scientific journal, Toxicon.
Campaigners claim that pollution could be making algal blooms worse, and point out that seals are also shot by fish farmers and fishermen. "Our government should immediately stop issuing licenses to shoot seals and launch a full investigation into what is causing seals to resort to cannibalism and fund more research into the cause and effect of toxic algal blooms," said John Robins of Save Our Seals Fund.