Most sus Thhi places I've ever been in serve saki with the sushi, which, I recall from an earlier post of yours, Thomas, is apparently not what the purists elect for due to its being fermented from rice (which would presumably also count out rice-based beers, although perhaps they aren't as bad as saki). There are a few large-chain sushi restaurant chains in the UK at the moment--they ain't afraid to charge either--and what they serve is NOT good. I'm 99% sure that none of it is even prepared on site, and I am slightly worried about one chain, who shall remain nameless, that also makes sushi-plates for supermarkets (and having tried supermarket sushi, which was also "NOT good", I wouldn't be surprised if they were one and the same thing as what they serve in the restaurant). PLUS, and I'm no authority here, but a lot of these chain places INSIST that you can only have your sake warm, which bemuses me slightly as I understood that sake was only meant to be drunk warm when it was cold outside (might be wrong on this). I don't like sake warm anyway (seems to lose what flavour it has when heated).
Interesting about fresh-water fish.