The Loire, a lovely big river with some real biggies of all species in it (for example, I saw a 20-plus zander taken on a "leurre souple", the 'rubber fish' that were taking France by storm in the early 1980s and which we've only got round to using over the past decade ... cor, did they once catch me some mahseer...).
Try visiting the Favri Peche tackle shop in Angers, about thirty miles from Saumur - when I was there to see its owner thirty years ago I was staggered by the sheer Gallic enthusiasm for all things fishy, impressed by the skill of the anglers, the owner's customers, I was taken out one misty winter's morning to watch.