Mystery Seal deaths

Very interesting image of a seal recently killed off Great Britain in The UK Sun. It appears that there is a continuous circular laceration that corkscrews from the head to the tail. They seem to have eliminated a lot of potential causes such as propellers and sharks. the continuous nature of the wound makes you think that they rotated through the blade much like an impeller in a turbine.
Sad , but an interesting puzzle.

Universal News And Sport
Science sleuths have been hunting for the 'murder weapon' since the first seals started dying last year, but they are still clueless? Now they are appealing to Sun readers to see if you can solve the mystery?
Horrified scientists have found around 60 carcasses so far? Most of the seals were spotted off the Norfolk coast, but ten more have been discovered at St Andrew's on the east coast of Scotland?
The cut goes all the way around the seals' bodies from head to stomach like a CORKSCREW ?
Professors have so far eliminated sharks, tidal power generators and ordinary boat propellers from the list of suspects - but they have no idea what else could have caused the injuries?
The search is now on for a mystery vessel that could have inflicted the mechanical wounds?
Top mammal scientist Callan Duck told The Sun: "It's a very clean cut - it looks like one single cut? If you're cutting a loaf of bread, there's a sawing action and you leave jagged edges, but there are none of those, so it looks like one continuous movement?
"The skin has been ripped clean off the seals' jaws? It would take hours to do that with a scalpel yourself?" The clever animals have learnt to avoid swimming too close to ships, leaving Mr Duck's team puzzled that they seem to have swum into the blade HEAD FIRST ?
He added: "Seals are pretty savvy creatures and they won't approach an obvious threat, but very suddenly they're being dragged head first into a rotating blade?"
The Scottish killings have already hit ten per cent of the breeding population of se als - and scientists are worried that the species could soon be wiped out entirely?
The seal team at St Andrew's University has already asked the RSPCA, the National Trust and even the Scottish Government to solve the mystery - with no luck?
The baffled experts are now hoping Sun readers can piece together the puzzle for them?
Mr Duck said: "It's a good mystery? We do believe it's solvable? Once we find out where, we can move on to why and what?
"We'd like to encourage members of the public to call in and make suggestions?"
Experts are also keen for any snaps of the dead seals? Mr Duck added: "They can be smelly but please take a picture?"