Matt and D3, thanks for your insights. I think you are right that to concentrate on small estuaries would be the right thing. I know that Atlantics near river mouths stick close to shore because most of the commercial drift nets used to set them there in the 70s when there were commercial fisheries for Atlantics in Canada. I have seen people casting around Tide-head at the Restigouche and the river is 100s of metres wide there. Never have I seen anyone catch anything and they may simply be doing it because the Restigouche is pretty well all private water above that so that is their only chance.
Atlantics do tend to come up in waves with the rain and don't usually hang around the lower river if they don't have to. So I suppose they wont be looking around much if they are on the move. I have heard people say that Atlantics will come up into the fresh into the first pool on high tide and then drop back if conditions don't seem right. I somehow doubt it though as that transition between salt and fresh is likely to be too hard on them to repeatedly subject themselves to it.
In the Swedish Baltic I think most of the Atlantics are caught by trolling close to rivers but I am not sure if those fish are resident there all year or are on the move and have the urge to get up the river.
My guess is that a big gaudy fly that may imitate their most recent food is probably the best bet. It seems to me that the productive flies for Atlantics get smaller as the season progresses.
Please keep posting anyone with ideas.