I don't know about migratory browns on the west here, but there is some anecdotal evidence that the bigger char in one system move between lochs, not just to spawn, these are char that have been seen, at around 2 1/2 lb, moving through a 3 loch system,with a 4 mile river, so migratory browns in a similar situation would not be unusual, and the don is a decent sized system,easgach 1