That makes for a delicious fish and chips indeed! In fact, a number of people argue that rock salmon was the original fish used in London for fish and chips! It has progressively gone out of fashion for reasons I ignore (apart from the fact that it is admittedly rather ugly, almost like a cross between salmon and eel, but hey, it's not as though delicious fish like lamprey and monkfish were particularly suited for the catwalk either). BTW, as I seem to remember that you now spend significant parts of your time in France, in the unlikely case you haven't found it yet, you'll get the rock salmon under the name of "saumonette"!