THE families of the five men who died when Mallaig fishing boat the Silvery Sea collided with a German freighter off Denmark two years ago are convinced that whoever was on watch must have suffered a heart attack or a brain haemorrhage prior to the accident.

They will never know, however, because no post-mortem examinations were carried out by the Danish authorities.

A statement from the families of skipper Alexander Manson, 57, from Mallaig, and crewmen Alexander Mackenzie, 32, and Michael Dyer, 36, both from Arisaig, Alan MacDonald, 31, from Morar and Billy Tait from Fraserburgh, was issued yesterday, in response to the publication of the Marine Accident Investigation Branch's report on the accident.

The MAIB found that the Silvery Sea did not meet her international obligations to keep out of the way of freighter Merkur, while the chief officer of the German ship did not take appropriate action early enough to best avoid an accident.

In the early hours of June 14 1998, the Silvery Sea had been on passage from the fishing grounds near the entrance to the Firth Of Forth to Esbjerg in Denmark, fully loaded with a catch of sand eels. The Merkur was sailing from Hamburg to Gothenburg partly loaded with containers.

According to the MAIB: ''Shortly after 05.30, Merkur's chief officer saw an echo on the edge of his radar screen. It was on his port bow at a range of seven miles. As the bearing of the echo did not change, he assessed that a risk of collision existed, and by International Regulations for Preventing Collisions at Sea it was the fishing vessel's responsibility to keep out of the way of the vessel on her starboard bow, the German container ship. The chief officer, in the stand-on vessel, maintained his course and speed.

''There is some doubt as to whether or not the chief officer left the bridge before collision. However, the evidence indicates that at 06.00, he plotted Merkur's position and entered it into the deck logbook. He then returned to the navigation console and saw that the fishing vessel had taken no avoiding action. Realising there was a risk of an imminent collision, he sounded a warning signal on the whistle. The fishing boat did not respond, and although Merkur's chief officer altered course to starboard, it was too late and the two vessels collided.

''The fishing vessel sank very quickly. Merkur's chief officer sounded the general alarm, called the master and made a distress call.''

Yesterday the bereaved families welcomed the report, which they described as ''a very fair document'' and thanked the MAIB for the sensitive way in which it had carried out its investigations, whose purpose was not to attribute blame.

They continued: ''The conclusions of the report depend upon a number of assumptions which are often made without supporting evidence. Therefore it will never be known precisely why, as stated in the report, such a well run and highly disciplined vessel as the Silvery Sea, failed to make the appropriate course alteration. However, it was established by the German inquiry, and restated in the MAIB report that the first officer aboard the Merkur acted incorrectly.

''We are persuaded that some unprecedented disaster had affected the watchkeeper aboard Silvery Sea, such as a cardiac arrest, and there is some evidence to support this. We regret that following the accident no post mortems were carried out, which would have allowed this to be substantiated . . .

''The report suggests that had the weather tight door in the forward bulkhead been closed the vessel would probably have survived.''

The families also welcomed the move by the MAIB to draw the Crown Office's attention to the failure to carry out post-mortem examinations and its recommendation that procedures be reviewed.