The victims are seals. Since January the headless bodies of more than 40 have been washed up. The police and the Scottish Society for the Prevention of Cruelty to Animals are investigating.
The divers found the bodies of seals that had been tied round their necks and weighted down. The find indicates that the decapitated bodies are only a fraction of the number being slain.
The seal population has been building again after being devastated by a virus in 1988-89. It is estimated that there are now 6,500 common and 18,000 grey seals in the north Scottish waters.
One theory is that the killers are disgruntled salmon farmers. The fish-farming industry is suffering hard times and seals are a nuisance. Nets are available to deter them but some farmers are unwilling to pay the cost. A bullet or knife is considered easier.
The SSPCS has been using infra-red nightsights in operations to try to catch the culprits. It has received information about who is responsible. 'At first it was an uphill task but recently we have had people coming forward,' said Mike Lynch, an inspector with the society. 'Fish farmers are having problems. People look for a scapegoat and the seals are an obvious target. What is being done is madness. There is no real gain.'
During the close season, when culling seals is illegal, the animals stay with their pups on the beach or close to the shore. It is thought they are being shot in the head which then is cut off because it will sink, while the body floats; so the bullet cannot be recovered to provide incriminating evidence.
The fish-farming and lobster creel fishing communities have called for an annual cull to protect their industries.