have a look at
not very cheery reading but it gives some information which may be of use
'In the UK sector, guard vessels have, commonly, been drawn from the fishing fleet, which suits the needs of both industries. From the oil industry perspective, they are confident that they are using experienced seafarers who know the North Sea, are able to cope with the harsh conditions often found in winter, and can liaise well with other fishing vessels actively engaged in fishing. For the fishermen, it provides a welcome boost to their income without being as physically demanding, or dangerous, as fishing operations.
A single UK company, SFF Services Ltd, Aberdeen (SFF), provides the necessary intermediary services between the two industries. SFF draws up a list of candidate guard ship vessels on a register and provides instructions on the work to be carried out, the duration, location and other relevant information to the delegated vessels.'