Now the days are shortening I am dipping into my fishing book library and am currently reading(?) Buller's "Domesday book of salmon". There are some interesting numbers on catches a century or so back. For instance the 8th Duke of Roxburgh spent a month Alta for 17 years catching over 1000 fish with one at 53lbs and 7 over 40lbs. All on fly.
What comes to mind though is that a large proportion of the big fish came from the Alta in Norway and in the Uk , the Awe. Now the Awe is a shadow of its foremr self for it is used for hydro electric generation. Prior to that along with the Alta is was a very fast flowing river. So my question is do big fish prefer powerful rivers of do they have to be big to negotiate them?

A lot of rivers are but shadows of their former selfs due to abstraction etc.
My opinion is that the longest most powerful rivers tend to have the earliest running and largest salmon.

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There maybe something in this. Look at the monster fish that used to come from the Aaro (Aaroy) - has anyone heard about this river recently?) and of course the Vosso (sadly no more) Do fast rivers breeed them big and strong to take on the current?

I have wondered if it something to do with the substrate size. I.e. you have to be big to spawn successfully in orange to football sized cobble!

Also maximum swimming speed is proportional to length so chutes and waterfalls can often be size selecting.

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